malaria information essay

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Health and medicine

Course: health and medicine   >   unit 13, what is malaria.

• The basics of malaria
• Diagnosing malaria
• Treatment of malaria
• Preventing malaria

How does malaria cause disease?

• If you are bitten by a mosquito carrying malaria parasites, it injects them into your bloodstream in the form of sporozoites (a spore-like form). Sporozoites travel in your blood until they reach and infect your liver cells.
• Over 5-16 days, the time depends on which species of malaria you have, the sporozoites multiply and mature, producing tens of thousands of young adults, called merozoites, inside each liver cell. For some species, the merozoites remain dormant, but may reactivate weeks or months later.
• When they are ready, the young adult parasites leave your liver cells for your bloodstream where they infect red blood cells. This begins a cycle of asexual reproduction in which broods of thousands of newly formed merozoites are produced and released over 1-3 days (again, the time depends on which species of malaria you have). It is the cyclical release of broods of merozoites into your bloodstream during this stage that causes the periodic feverish symptoms of malaria. Importantly, not all merozoites are destined for an asexual existence, some develop sexually instead. This produces male and female forms (gametocytes) that your blood cells carry around in your bloodstream.
• Now when another mosquito bites you, it ingests blood cells containing gametocytes. The mosquito digests the blood cells, releasing the male and female gametes, which fuse together and burrow into the mosquito’s gut wall, where they mature inside oocysts.
• After 8-15 days (depending on the species) the oocysts burst and sporozoites are released into the body cavity of the mosquito. From there, they travel to the salivary glands, leaving the mosquito primed to transmit malaria parasites to new hosts.

What are the symptoms of malaria?

Situations that increases your chances of getting malaria.

• Sub-Saharan Africa,
• The Indian subcontinent
• South Pacific Islands (Solomon Islands, Papua New Guinea)
• Haiti (in the Caribbean)

How likely are you to get malaria?

Risk of malaria around the world, what steps can you take to prevent malaria.

• Assess your risk . The chances of getting malaria are largely based on when and where you are going – May to December are prime months for contracting malaria, particularly in sub-Saharan Africa, the Indian subcontinent, and Southeast Asia, and especially during and after the rainy season. Before you leave, check out your local disease control center for disease prevention information. You need to know the level of risk and the recommended type of prevention to deal with the risk. Then, get prepared.
• Take personal protection . Your first lines of defense against mosquito bites are mosquito repellent and mosquito nets. These are recommended wherever and whenever there is any risk of malaria. Apply insect repellent in the early evening, before the mosquitos are out looking for dinner, and sleep behind insecticide-treated bed nets. These are around twice as effective as untreated nets, and this combination approach gives you the maximum personal protection against mosquito bites. 2 , 3 ‍  
• Take additional measures . Not all malaria parasites are created equal, so if you are traveling to a region that is known to have mosquitos with the more prevalent and dangerous types ( P. vivax and P. falciparum ) you will need additional defenses to protect you. These come in the form of preventative medications that can stop the parasites in their tracks after they get into your bloodstream. You may have to take these medications before, during and after you return from your travels, and to have them work properly, you need to be sure to take them as directed.

What treatments are available for malaria?

• the type of parasite you are infected with
• where and when you got infected
• how severe your symptoms are
• if you have other illnesses or conditions, are taking other medication, and/or have drug allergies
• whether or not you are pregnant
• whether or not the parasites in the region where you were infected are resistant to any of the available antimalarial drugs ( is the parasite resistant to treatment? ).

Consider the following:

• People who were born and raised, or who lived as a child in a region where malaria occurs, but who as adults are living in a malaria-free country, are often at extremely high risk of getting malaria when they return for a visit. Why would that be? First, any immunity to malaria that they may have gained through childhood exposure decreases with time. Although they may not realize it, this means that like other non-immune travellers they are very vulnerable to the disease if they get bitten by an infected mosquito. Second, people visiting friends and family are more likely to travel to remote regions where malaria transmission rates may be particularly high. Lack of awareness of the need to take precautions against mosquito bites puts travelers visiting friends and family at particularly high risk of disease.
• If you are bitten with P. vivax malaria, you may feel fine between attacks, and even without treatment, the paroxysms will most likely subside in a few weeks. However, if you get P. falciparum malaria, you are likely to feel unwell even between attacks and, without treatment, you may die. Why do you think this might be? One explanation is that the P. falciparum malaria infects red blood cells, regardless of whether they are young or old, producing very high numbers of parasites in the blood. P. vivax , on the other hand, only infects young red blood cells, which limits the number of parasites that can accumulate.

Attributions

• WHO (2014). World malaria report 2014. World Health Organization. Retrieved from: http://www.who.int/malaria/publications/world_malaria_report_2014/wmr-2014-no-profiles.pdf?ua=1
• Lengeler, C. (2004). Insecticide-treated bed nets and curtains for preventing malaria. Cochrane Database Syst Rev, 2(2).
• Hill, N., Lenglet, A., Arnéz, A. M., & Carneiro, I. (2007). Plant based insect repellent and insecticide treated bed nets to protect against malaria in areas of early evening biting vectors: double blind randomised placebo controlled clinical trial in the Bolivian Amazon. BMJ : British Medical Journal, 335(7628), 1023.
• Plasmodium vivax blood smear: By Photo Credit: Content Providers(s): CDC/ Steven Glenn, Laboratory & Consultation Division Transwiki approved by: w:en:User:Dmcdevit [Public domain], via Wikimedia Commons.
• Plasmodium falciparum blood smear: By Photo Credit: Content Providers(s): CDC/Dr. Mae Melvin Transwiki approved by: w:en:User:Dmcdevit [Public domain], via Wikimedia Commons.
• Plasmodium ovale blood smear: By Photo Credit: Content Providers(s): CDC/ Steven Glenn, Laboratory & Consultation Division Transwiki approved by: w:en:User:Dmcdevit [Public domain], via Wikimedia Commons.
• Plasmodium malariae blood smear: By Photo Credit: Content Providers: CDC/Dr. Mae Melvin [Public domain], via Wikimedia Commons.

Malaria: Obstacles and Opportunities (1991)

Chapter: 1. conclusions and recommendations, conclusions and recommendations, defining the problem.

The outlook for malaria control is grim. The disease, caused by mosquito-borne parasites, is present in 102 countries and is responsible for over 100 million clinical cases and 1 to 2 million deaths each year. Over the past two decades, efforts to control malaria have met with less and less success. In many regions where malaria transmission had been almost eliminated, the disease has made a comeback, sometimes surpassing earlier recorded levels. The dream of completely eliminating malaria from many parts of the world, pursued with vigor during the 1950s and 1960s, has gradually faded. Few believe today that a global eradication of malaria will be possible in the foreseeable future.

Worldwide, the number of cases of malaria caused by Plasmodium falciparum , the most dangerous species of the parasite, is on the rise. Drug-resistant strains of P. falciparum are spreading rapidly, and there have been recent reports of drug resistance in people infected with P. vivax , a less virulent form of the parasite. Furthermore, mosquitoes are becoming increasingly resistant to insecticides, and in many cases, have adapted so as to avoid insecticide-treated surfaces altogether.

In large part because of the spread of drug and insecticide resistance, there are fewer tools available today to control malaria than there were 20 years ago. In many countries, the few remaining methods are often ap-

plied inappropriately. The situation in many African nations is particularly dismal, exacerbated by a crumbling health infrastructure that has made the implementation of any disease control program difficult.

Malaria cases among tourists, business travelers, military personnel, and migrant workers in malarious areas have been increasing steadily in the last several years, posing new concerns that the disease will be introduced to currently nonmalarious areas. Recent epidemics have claimed tens of thousands of lives in Africa, and there is an increasing realization that malaria is a major impediment to socioeconomic development in many countries. Unless practical, cost-effective strategies can be developed and successfully implemented, malaria will continue to exact a heavy toll on human life and health around the world.

Although often considered a single disease, malaria is more accurately viewed as many diseases, each shaped by subtle interactions of biologic, ecologic, social, and economic factors. The species of parasite, the behavior of the mosquito host, the individual's immune status, the climate, human activities, and access to health services all play important roles in determining the intensity of disease transmission, who will become infected, who will get sick, and who will die.

Gem miners along the Thailand-Cambodia border, American tourists on a wildlife safari in East Africa, villagers living on the central highlands in Madagascar, residents of San Diego County, California, a young pregnant woman in Malawi, Swiss citizens living near Geneva International Airport, children in Africa south of the Sahara, and a U.S. State Department secretary in Tanzania seem to have little in common, yet they are all at risk of contracting malaria. Because of the disease's variable presentations, each will be affected differently, as illustrated below.

For the hundreds of thousands of Thai seasonal agricultural workers who travel deep into the forest along the Thailand-Cambodia border to mine for gems, malaria is the cost of doing business. These young men are exposed to aggressive forest mosquitoes, and within two to three weeks after arriving, almost every miner will get malaria. Many gem miners seek medications to prevent and self-treat mild cases of the disease. But because malaria in this part of the world is resistant to most antimalarial drugs, the few effective drugs are reserved for the treatment of confirmed cases of malaria. To complicate matters, there are no health services in the forest to treat patients, and the health clinics in Thailand are overburdened by the high demand for treating those with severe malaria, most of whom are returning gem miners. A similar scenario involving over 400,000 people exists among gold miners in Rondonia, Brazil.

Each year, over seven million U.S. citizens visit parts of the world

where malaria is present. Many, at the recommendation of their travel agent or physician, take antimalarial medications as a preventive measure, but a significant number do not. Tourists and other travelers who have never been exposed to malaria, and therefore have never developed protective immunity, are at great risk for contracting severe disease. Ironically, it is not the infection itself that poses the biggest danger, but the chance that treatment will be delayed because of misdiagnosis upon the individual's return to the United States. Most U.S. doctors have never seen a patient with malaria, are often confused by the wide array of symptoms, and are largely unaware that malaria in a nonimmune person can be a medical emergency, sometimes rapidly fatal.

Prior to 1950, malaria was the major cause of death in the central highlands of the African island nation of Madagascar. In the late 1950s, an aggressive program of indoor insecticide spraying rid the area of malaria-carrying mosquitoes, and malaria virtually disappeared. By the 1970s, confident of a victory in the battle against malaria, Madagascar began to phase out its spraying program; in some areas spraying was halted altogether. In the early 1980s, the vector mosquitoes reinvaded the central highlands, and in 1986 a series of devastating epidemics began. The older members of the population had long since lost the partial immunity they once had, and the younger island residents had no immunity at all. During the worst of the epidemics, tens of thousands of people died in one three-month period. The tragedy of this story is that it could have been prevented. A cheap antimalarial drug, chloroquine, could have been a powerful weapon in Madagascar, where drug resistance was not a significant concern. Because of problems in international and domestic drug supply and delivery, however, many people did not receive treatment and many died. In the last 18 months, surveillance has improved, spraying against the mosquito has resumed, and more effective drug distribution networks have been established. Malaria-related mortality has declined sharply as a result.

Malaria, once endemic in the southern United States, occurs relatively infrequently. Indeed, there have been only 23 outbreaks of malaria since 1950, and the majority of these occurred in California. But for each of the past three years, the San Diego County Department of Health Services has had to conduct an epidemiologic investigation into local transmission of malaria. An outbreak in the late summer of 1988 involved 30 persons, the largest such outbreak in the United States since 1952. In the summer of 1989, three residents of San Diego County—a migrant worker and two permanent residents—were diagnosed with malaria; in 1990, a teenager living in a suburb of San Diego County fell ill with malaria. All of the cases were treated successfully, but these incidents raise questions about the possibility of new and larger outbreaks in the future. Malaria

transmission in San Diego County (and in much of California) is attributed to the presence of individuals from malaria-endemic regions who lack access to medical care, the poor shelter and sanitation facilities of migrant workers, and the ubiquitous presence of Anopheles mosquitoes in California.

A 24-year-old pregnant Yao woman from the Mangochi District in Malawi visited the village health clinic monthly to receive prenatal care. While waiting to be seen by the health provider, she and other women present listened to health education talks which were often about the dangers of malaria during pregnancy, and the need to install screens around the house to keep the mosquitoes away, to sleep under a bednet, and to take a chloroquine tablet once a week. Toward the end of her second trimester of pregnancy, the woman returned home from her prenatal visit with her eight tablets of chloroquine wrapped in a small packet of brown paper. She promptly gave the medicine to her husband to save for the next time he or one of their children fell ill. The next week she developed a very high malarial fever and went into labor prematurely. The six-month-old fetus was born dead.

Over a two-week period in the summer of 1989, five Swiss citizens living within a mile of Geneva International Airport presented at several hospitals with acute fever and chills. All had malaria. Four of the five had no history of travel to a malarious region; none had a history of intravenous drug use or blood transfusion. Apart from their symptoms, the only thing linking the five was their proximity to the airport. A subsequent epidemiologic investigation suggested that the malaria miniepidemic was caused by the bite of stowaway mosquitoes en route from a malaria-endemic country. The warm weather, lack of systematic spraying of aircraft, and the close proximity of residential areas to the airport facilitated the transmission of the disease.

Malaria is a part of everyday life in Africa south of the Sahara. Its impact on children is particularly severe. Mothers who bring unconscious children to the hospital often report that the children were playing that morning, convulsed suddenly, and have been unconscious ever since. These children are suffering from the most frequently fatal complication of the disease, cerebral malaria. Other children succumb more slowly to malaria, becoming progressively more anemic with each subsequent infection. By the time they reach the hospital, they are too weak to sit and are literally gasping for breath. Many children are brought to hospitals as a last resort, after treatment given for “fever” at the local health center has proved ineffective. Overall, children with malaria account for a third of all hospital admissions. A third of all children hospitalized for malaria die. In most parts of Africa, there are no effective or affordable options to prevent the

disease, so children are at high risk until they have been infected enough times to develop a partial immunity.

A 52-year-old American woman, the secretary to the U.S. ambassador in Tanzania, had been taking a weekly dose of chloroquine to prevent malaria since her arrival in the country the year before. She arrived at work one morning complaining of exhaustion, a throbbing headache, and fever. A blood sample was taken and microscopically examined for malaria parasites. She was found to be infected with P. falciparum , and was treated immediately with high doses of chloroquine. That night, she developed severe diarrhea, and by morning she was found to be disoriented and irrational. She was diagnosed as having cerebral malaria, and intravenous quinine treatment was started. Her condition gradually deteriorated—she became semicomatose and anemic, and approximately 20 percent of her red blood cells were found to be infected with malaria parasites. After continued treatment for several days, no parasites were detected in her blood. Despite receiving optimal care, other malaria-related complications developed and she died just nine days after the illness began. The cause of death: chloroquine-resistant P. falciparum .

These brief scenarios give a sense of the diverse ways that malaria can affect people. So fundamental is this diversity with respect to impact, manifestation, and epidemiology that malaria experts themselves are not unanimous on how best to approach the disease. Malariologists recognize that malaria is essentially a local phenomenon that varies greatly from region to region and even from village to village in the same district. Consequently, a single global technology for malaria control is of little use for specific conditions, yet the task of tailoring strategies to each situation is daunting. More important, many malarious countries do not have the resources, either human or financial, to carry out even the most meager efforts to control malaria.

These scenarios also illustrate the dual nature of malaria as it affects U.S. policy. In one sense, it is a foreign aid issue; a devastating disease is currently raging out of control in vast, heavily populated areas of the world. In another sense, malaria is of domestic public health concern. The decay of global malaria control and the invasion of the parasite into previously disease-free areas, coupled with the increasing frequency of visits to such areas by American citizens, intensify the dangers of malaria for the U.S. population. Tourists, business travelers, Peace Corps volunteers, State Department employees, and military personnel are increasingly at risk, and our ability to protect and cure them is in jeopardy. What is desperately needed is a better application of existing malaria control tools and new methods of containing the disease.

In most malarious regions of the world, there is inadequate access to malaria treatment. Appropriate health facilities may not exist; those that do exist may be inaccessible to affected populations, may not be supplied with effective drugs, or may be staffed inappropriately. In many countries, the expansion of primary health care services has not proceeded according to expectations, particularly in the poorest (and most malarious) nations of the tropical world.

In some countries, antimalarial interventions are applied in broad swaths, without regard to underlying differences in the epidemiology of the disease. In other countries, there are no organized interventions at all. The malaria problem in many regions is compounded by migration, civil unrest, poorly planned exploitation of natural resources, and their frequent correlate, poverty.

During the past 15 years, much research has focused on developing vaccines for malaria. Malaria vaccines are thought to be possible in part because people who are naturally exposed to the malaria parasite acquire a partial immunity to the disease over time. In addition, immunization of animals and humans by the bites of irradiated mosquitoes infected with the malaria parasite can protect against malaria infection. Much progress has been made, but current data suggest that effective vaccines are not likely to be available for some time.

Compounding the difficulty of developing more effective malaria prevention, treatment, and control strategies is a worldwide decline in the pool of scientists and health professionals capable of conducting field research and organizing and managing malaria control programs at the country level. With the change in approach from malaria eradication to malaria control, many malaria programs “lost face,” admitting failure and losing the priority interest of their respective ministries of health. As external funding agencies lost interest in programs, they reduced their technical and financial support. As a consequence, there were fewer training opportunities, decreased contacts with international experts, and diminished prospects for improving the situation. Today, many young scientists and public health specialists, in both the developed and developing countries, prefer to seek higher-profile activities with better defined opportunities for career advancement.

It is against this backdrop of a worsening worldwide malaria situation that the Institute of Medicine was asked to convene a multidisciplinary committee to assess the current status of malaria research and control and to make recommen-

dations to the U.S. government on promising and feasible strategies to address the problem. During the 18-month study, the committee reviewed the state of the science in the major areas of malariology, identified gaps in knowledge within each of the major disciplines, and developed recommendations for future action in malaria research and control.

Organization

Chapter 2 summarizes key aspects of the individual state-of-the-science chapters, and is intended to serve as a basic introduction to the medical and scientific aspects of malaria, including its clinical signs, diagnosis, treatment, and control. Chapter 3 provides a historical overview of malaria, from roughly 3000 B.C. to the present, with special emphasis on efforts in this century to eradicate and control the disease. The state-of-the-science reviews, which start in Chapter 4 , begin with a scenario titled “Where We Want To Be in the Year 2010.” Each scenario describes where the discipline would like to be in 20 years and how, given an ideal world, the discipline would have contributed to malaria control efforts. The middle section of each chapter contains a critical review of the current status of knowledge in the particular field. The final section lays out specific directions for future research based on a clear identification of the major gaps in scientific understanding for that discipline. The committee urges those agencies that fund malaria research to consult the end of each state-of-the-science chapter for suggestions on specific research opportunities in malaria.

Sponsorship

This study was sponsored by the U.S. Agency for International Development, the U.S. Army Medical Research and Development Command, and the National Institute of Allergy and Infectious Diseases of the National Institutes of Health.

CONCLUSIONS AND RECOMMENDATIONS

A major finding of the committee is the need to increase donor and public awareness of the growing risk presented by the resurgence of malaria. Overall, funding levels are not adequate to meet the problem. The committee believes that funding in the past focused too sharply on specific technologies and particular control strategies (e.g., indiscriminate use of insecticide spraying). Future support must be balanced among the needs outlined in this report. The issue for prioritization is not whether to select specific technologies or control strategies, but to raise the priority for solv-

ing the problem of malaria. This is best done by encouraging balanced research and control strategies and developing a mechanism for periodically adjusting support for promising approaches.

This report highlights those areas which the committee believes deserve the highest priority for research or which should be considered when U.S. support is provided to malaria control programs. These observations and suggestions for future action, presented below in four sections discussing policy, research, control, and training, represent the views of a multidisciplinary group of professionals from diverse backgrounds and with a variety of perspectives on the problem.

The U.S. government is the largest single source of funds for malaria research and control activities in the world. This investment is justified by the magnitude of the malaria problem, from both a foreign aid and a public health perspective. The increasing severity of the threat of malaria to residents of endemic regions, travelers, and military personnel, and our diminishing ability to counter it, should be addressed by a more comprehensive and better integrated approach to malaria research and control. However, overall U.S. support for malaria research and control has declined over the past five years. The committee believes that the amount of funding currently directed to malaria research and control activities is inadequate to address the problem.

Over the past 10 years, the majority of U.S. funds available for malaria research have been devoted to studies on immunity and vaccine development. Although the promise of vaccines remains to be realized, the committee believes that the potential benefits are enormous. At the same time, the relative paucity of funds available for research has prevented or slowed progress in other areas. Our incomplete knowledge about the basic biology of malaria parasites, how they interact with their mosquito and human hosts, and how human biology and behavior affect malaria transmission and control remains a serious impediment to the development and implementation of malaria control strategies. The committee believes that this situation must be addressed without reducing commitment to current research initiatives. The committee further believes that such research will pay long-term dividends in the better application of existing tools and the development of new drugs, vaccines, and methods for vector control.

The committee recommends that increased funds be made available so that U.S. research on malaria can be broadened according to the priorities addressed in this report, including laboratory and field research on the biology of malaria parasites, their mosquito vectors, and their interaction with humans.

The committee believes that the maximum return on investment of funds devoted to malaria research and control can be achieved only by rigorous review of project proposals. The committee further believes that the highest-quality review is essential to ensure that funding agencies spend their money wisely. The committee believes that all U.S.-supported malaria field activities, both research and control, should be of the highest scientific quality and relevance to the goals of malaria control.

The committee recommends decisions on funding of malaria research be based on scientific merit as determined by rigorous peer review, consistent with the guidelines of the National Institutes of Health or the United Nations Development Program/World Bank/ World Health Organization Special Programme for Research and Training in Tropical Diseases, and that all U.S.-supported malaria field projects be subject to similar rigorous review to ensure that projects are epidemiologically and scientifically sound.

Commitment and Sustainability

For malaria control, short-term interventions can be expected to produce only short-term results. The committee believes that short-term interventions are justified only for emergency situations. Longer-term interventions should be undertaken only when there is a national commitment to support sustained malaria surveillance and control.

The committee recommends that malaria control programs receive sustained international and local support, oriented toward the development of human resources, the improvement of management skills, the provision of supplies, and the integration of an operational research capability in support of an epidemiologically sound approach to malaria control.

Surveillance

During the major effort to eradicate malaria from many parts of the world that began in the late 1950s and ended in 1969, it was important to establish mechanisms to detect all malaria infections. As a result, systems were established in many countries to collect blood samples for later microscopic examination for the presence of parasites. Each year, the results from more than 140 million slides are reported to the World Health Organization, of which roughly 3 to 5 percent are positive for malaria. This approach seeks to answer the question posed 30 years ago: How many people are infected with the malaria parasite? It does not answer today's questions: Who is sick? Where? Why? The committee concludes that the mass collection of blood slides requires considerable resources, poses seri-

ous biosafety hazards, deflects attention from the treatment of ill individuals, and has little practical relevance for malaria control efforts today.

Instead of the mass collection of slides, the committee believes that the most effective surveillance networks are those that concurrently measure disease in human populations, antimalarial drug use, patterns of drug resistance, and the intensity of malaria transmission by vector populations. The committee believes that malaria surveillance practices have not received adequate recognition as an epidemiologic tool for designing, implementing, and evaluating malaria control programs.

The committee recommends that countries be given support to orient malaria surveillance away from the mass collection and screening of blood slides toward the collection and analysis of epidemiologically relevant information that can be used to monitor the current situation on an ongoing basis, to identify high-risk groups, and to detect potential epidemics early in their course.

Inter-Sectoral Cooperation

The committee believes that insufficient attention has been paid to the impact that activities in non-health-related sectors, such as construction, industry, irrigation, and agriculture, have on malaria transmission. Conversely, there are few assessments of the impact of malaria control projects on other public health initiatives, the environment, and the socioeconomic status of affected populations. Malaria transmission frequently occurs in areas where private and multinational businesses and corporations (e.g., hotel chains, mining operations, and industrial plants) have strong economic interests. Unfortunately and irresponsibly, some local and multinational businesses contribute few if any resources to malaria control in areas in which they operate.

The committee recommends greater cooperation and consultation between health and nonhealth sectors in the planning and implementation of major development projects and malaria activities. It also recommends that all proposed malaria control programs be analyzed for their potential impact on other public health programs, the environment, and social and economic welfare, and that local and multinational businesses be recruited by malaria control organizations to contribute substantially to local malaria control efforts.

New Tools for Malaria Control

The committee believes that, as a policy directive, it is important to support research activities to develop new tools for malaria control. The

greatest momentum for the development of new tools exists in vaccine and drug development, and the committee believes it essential that this momentum be maintained. The committee recognizes that commendable progress has been made in defining the characteristics of antigens and delivery systems needed for effective vaccines, but that the candidates so far tested fall short of the goal. Much has been learned which supports the hope that useful vaccines can be developed. To diminish activity in vaccine development at this stage would deal a severe blow to one of our best chances for a technological breakthrough in malaria control.

The committee recommends that vaccine development continue to be a priority of U.S.-funded malaria research.

Only a handful of drugs are available to prevent or treat malaria, and the spread of drug-resistant strains of the malaria parasite threatens to reduce further the limited pool of effective drugs. The committee recognizes that there is little economic incentive for U.S. pharmaceutical companies to undertake antimalarial drug discovery activities. The committee is concerned that U.S. government support of these activities, based almost entirely at the Walter Reed Army Institute of Research (WRAIR), has decreased and is threatened with further funding cuts. The committee concludes that the WRAIR program in antimalarial drug discovery, which is the largest and most successful in the world, is crucial to international efforts to develop new drugs for malaria. The benefits of this program in terms of worldwide prevention and treatment of malaria have been incalculable.

The committee strongly recommends that drug discovery and development activities at WRAIR receive increased and sustained support.

The next recommendation on policy directions reflects the committee 's concern about the lack of involvement in malaria research by the private sector. The committee believes that the production of candidate malaria vaccines and antimalarial drugs for clinical trials has been hampered by a lack of industry involvement. Greater cooperation and a clarification of the contractual relationships between the public and private sectors would greatly enhance the development of drugs and vaccines.

The committee recommends that mechanisms be established to promote the involvement of pharmaceutical and biotechnology firms in the development of malaria vaccines, antimalarial drugs, and new tools for vector control.

Coordination and Integration

The committee is concerned that there is inadequate joint planning and coordination among U.S.-based agencies that support malaria research and

control activities. Four government agencies and many nongovernmental organizations in the United States are actively involved in malaria-related activities. There are also numerous overseas organizations, governmental and nongovernmental, that actively support such activities worldwide.

The complexity and variability of malaria, the actual and potential scientific advances in several areas of malariology, and most important the worsening worldwide situation argue strongly for an ongoing mechanism to assess and influence current and future U.S. efforts in malaria research and control.

The committee strongly recommends the establishment of a national advisory body on malaria.

In addition to fulfilling a much needed coordinating function among U.S.-based agencies and between the U.S. and international efforts, the national advisory body could monitor the status of U.S. involvement in malaria research and control, assess the relevant application of knowledge, identify areas requiring further research, make recommendations to the major funding agencies, and provide a resource for legislators and others interested in scientific policy related to malaria. The national advisory body could convene specific task-oriented scientific working groups to review research and control activities and to make recommendations, when appropriate, for changes in priorities and new initiatives.

The committee believes that the national advisory body should be part of, and appointed by, a neutral and nationally respected scientific body and that it should actively encourage the participation of governmental and nongovernmental organizations, industry, and university scientists in advising on the direction of U.S. involvement in malaria research and control.

The increasing magnitude of the malaria problem during the past decade and the unpredictability of changes in human, parasite, and vector determinants of transmission and disease point strongly to the need for such a national advisory body, which can be responsive to rapidly changing problems, and advances in scientific research, relating to global efforts to control malaria.

Malaria Research Priorities

Malaria control is in crisis in many areas of the world. People are contracting and dying of severe malaria in unprecedented numbers. To address these problems, the committee strongly encourages a balanced research agenda. Two basic areas of research require high priority. Research that will lead to improved delivery of existing interventions for malaria, and the development of new tools for the control of malaria.

Research in Support of Available Control Measures

Risk Factors for Severe Malaria People who develop severe and complicated malaria lack adequate immunity, and many die from the disease. Groups at greatest risk include young children and pregnant women in malaria endemic regions; nonimmune migrants, laborers, and visitors to endemic regions; and residents of regions where malaria has been recently reintroduced. For reasons that are largely unknown, not all individuals within these groups appear to be at equal risk for severe disease. The committee believes that the determinants of severe disease, including risk factors associated with a population, the individual (biologic, immunologic, socioeconomic, and behavioral), the parasite, or exposure to mosquitoes, are likely to vary considerably in different areas.

The committee recommends that epidemiologic studies on the risk factors for severe and complicated malaria be supported.

Pathogenesis of Severe and Complicated Malaria Even with optimal care, 20 to 30 percent of children and adults with the most severe form of malaria—primarily cerebral malaria—die. The committee believes that a better understanding of the disease process will lead to improvements in preventing and treating severe forms of malaria. The committee further believes that determining the indications for treatment of severe malarial anemia is of special urgency given the risk of transmitting the AIDS virus through blood transfusions, the only currently available treatment for malarial anemia. Physicians need to know when it is appropriate to transfuse malaria patients.

The committee recommends greater support for research on the pathogenesis of severe and complicated malaria, on the mechanisms of malarial anemia, and on the development of specific criteria for blood transfusions in malaria.

Social Science Research The impact of drugs to control disease or programs to reduce human-mosquito contact is mediated by local practices and beliefs about malaria and its treatment. Most people in malaria-endemic countries seek initial treatment for malaria outside of the formal health sector. Programs that attempt to influence this behavior must understand that current practices satisfy, at some level, local concerns regarding such matters as access to and effectiveness of therapy, and cost. These concerns may lead to practices at odds with current medical practice. Further, many malaria control programs have not considered the social, cultural, and behavioral dimensions of malaria, thereby limiting the effectiveness of measures undertaken. The committee recognizes that control programs often fail to incorporate household or community concerns and resources

into program design. In most countries, little is known about how the demand for and utilization of health services is influenced by such things as user fees, location of health clinics, and the existence and quality of referral services. The committee concludes that modern social science techniques have not been effectively applied to the design, implementation, and evaluation of malaria control programs.

The committee recommends that research be conducted on local perceptions of malaria as an illness, health-seeking behaviors (including the demand for health care services), and behaviors that affect malaria transmission, and that the results of this research be included in community-based malaria control interventions that promote the involvement of communities and their organizations in control efforts.

Innovative Approaches to Malaria Control Malaria control programs will require new ideas and approaches, and new malaria control strategies need to be developed and tested. There is also a need for consistent support of innovative combinations of control technologies and for the transfer of new technologies from the laboratory to the clinic and field for expeditious evaluation. Successful technology transfer requires the exchange of scientific research, but more importantly, must be prefaced by an improved understanding of the optimal means to deliver the technology to the people in need (see Chapter 11 ).

The committee recommends that donor agencies provide support for research on new or improved control strategies and into how new tools and technologies can be better implemented and integrated into on-going control efforts.

Development of New Tools

Antimalarial Immunity and Vaccine Development Many people are able to mount an effective immune response that can significantly mitigate symptoms of malaria and prevent death. The committee believes that the development of effective malaria vaccines is feasible, and that the potential benefits of such vaccines are enormous. Several different types of malaria vaccines need to be developed: vaccines to prevent infection (of particular use for tourists and other nonimmune visitors to endemic countries), prevent the progression of infection to disease (for partially immune residents living in endemic areas and for nonimmune visitors), and interrupt transmission of parasites by vector populations (to reduce the risk of new infections in humans). The committee believes that each of these directions should be pursued.

The committee recommends sustained support for research to identify mechanisms and targets of protective immunity and to exploit the

use of novel scientific technologies to construct vaccines that induce immunity against all relevant stages of the parasite life cycle.

Drug Discovery and Development Few drugs are available to prevent or treat malaria, and the spread of drug-resistant strains of malaria parasites is steadily reducing the limited pool of effective chemotherapeutic agents. The committee believes that an inadequate understanding of parasite biochemistry and biology impedes the process of drug discovery and slows studies on the mechanisms of drug resistance.

The committee recommends increased emphasis on screening compounds to identify new classes of potential antimalarial drugs, identifying and characterizing vulnerable targets within the parasite, understanding the mechanisms of drug resistance, and identifying and developing agents that can restore the therapeutic efficacy of currently available drugs.

Vector Control Malaria is transmitted to humans by the bites of infective mosquitoes. The objective of vector control is to reduce the contact between humans and infected mosquitoes. The committee believes that developments are needed in the areas of personal protection, environmental management, pesticide use and application, and biologic control, as well as in the largely unexplored areas of immunologic and genetic approaches for decreasing parasite transmission by vectors.

The committee recommends increased support for research on vector control that focuses on the development and field testing of methods for interrupting parasite transmission by vectors.

Malaria Control

Malaria is a complex disease that, even under the most optimistic scenario, will continue to be a major health threat for decades. The extent to which malaria affects human health depends on a large number of epidemiologic and ecologic factors. Depending on the particular combination of these and other variables, malaria may have different effects on neighboring villages and people living in a single village. All malaria control programs need to be designed with a view toward effectiveness and sustainability, taking into account the local perceptions, the availability of human and financial resources, and the multiple needs of the communities at risk. If community support for health sector initiatives is to be guaranteed, the public needs to know much more about malaria, its risks for epidemics and severe disease, and difficulties in control.

Unfortunately, there is no “magic bullet” solution to the deteriorating worldwide malaria situation, and no single malaria control strategy will be applicable in all regions or epidemiologic situations. Given the limited available financial and human resources and a dwindling pool of effective

antimalarial tools, the committee suggests that donor agencies support four priority areas for malaria control in endemic countries.

The committee believes that the first and most basic priority in malaria control is to prevent infected individuals from becoming severely ill and dying. Reducing the incidence of severe morbidity and malaria-related mortality requires a two-pronged approach. First, diagnostic, treatment, and referral capabilities, including the provision of microscopes, training of technicians and other health providers, and drug supply, must be enhanced. Second, the committee believes that many malaria-related deaths could be averted if individuals and caretakers of young children knew when and how to seek appropriate treatment and if drug vendors, pharmacists, physicians, nurses, and other health care providers were provided with up-to-date and locally appropriate treatment and referral guidelines. The development and implementation of an efficient information system that provides rapid feedback to the originating clinic and area is key to monitoring the situation and preventing epidemics.

The committee believes that the second priority should be to promote personal protection measures (e.g., bednets, screens, and mosquito coils) to reduce or eliminate human-mosquito contact and thus to reduce the risk of infection for individuals living in endemic areas. At the present time, insecticide-treated bednets appear to be the most promising personal protection method.

In many environments, in addition to the treatment of individuals and use of personal protection measures, community-wide vector control is feasible. In such situations, the committee believes that the third priority should be low-cost vector control measures designed to reduce the prevalence of infective mosquitoes in the environment, thus reducing the transmission of malaria to populations. These measures include source reduction (e.g., draining or filling in small bodies of water where mosquito larvae develop) or the application of low-cost larval control measures. In certain environments, the use of insecticide-impregnated bednets by all or most members of a community may also reduce malaria transmission, but this approach to community-based malaria control remains experimental.

The committee believes that the fourth priority for malaria control should be higher cost vector control measures such as large-scale source reduction or widespread spraying of residual insecticides. In certain epidemiologic situations, the use of insecticides for adult mosquito control is appropriate and represents the method of choice for decreasing malaria transmission and preventing epidemics (see Chapter 7 and Chapter 10 ).

The committee recommends that support of malaria control programs include resources to improve local capacities to conduct prompt diagnosis, including both training and equipment, and to ensure the availability of antimalarial drugs.

The committee recommends that resources be allocated to develop and disseminate malaria treatment guidelines for physicians, drug vendors, pharmacists, village health workers, and other health care personnel in endemic and non-endemic countries. The guidelines should be based, where appropriate, on the results of local operational research and should include information on the management of severe and complicated disease. The guidelines should be consistent and compatible among international agencies involved in the control of malaria.

The committee recommends that support for malaria control initiatives include funds to develop and implement locally relevant communication programs that provide information about how to prevent and treat malaria appropriately (including when and how to seek treatment) and that foster a dialogue about prevention and control.

Organization of Malaria Control

One of the major criticisms of malaria control programs during the past 10 to 15 years has been that funds have been spent inappropriately without an integrated plan and without formal evaluation of the efficacy of control measures instituted. In many instances, this has led to diminished efforts to control malaria.

The committee strongly encourages renewed commitment by donor agencies to support national control programs in malaria-endemic countries.

The committee recommends that U.S. donor agencies develop, with the advice of the national advisory body, a core of expertise (either in-house or through an external advisory group) to plan assistance to malaria control activities in endemic countries.

The committee believes that the development, implementation, and evaluation of such programs must follow a rigorous set of guidelines. These guidelines should include the following steps:

Identification of the problem

Determine the extent and variety of malaria. The paradigm approach described in Chapter 10 should facilitate this step.

Analyze current efforts to solve malaria problems.

Identify and characterize available in-country resources and capabilities.

Development of a plan

Design and prioritize interventions based on the epidemiologic situation and the available resources.

Design a training program for decision makers, managers, and technical staff to support and sustain the interventions.

Define specific indicators of the success or failure of the interventions at specific time points.

Develop a specific plan for reporting on the outcomes of interventions.

Develop a process for adjusting the program in response to successes and/or failures of interventions.

Review of the comprehensive plan by a donor agency review board

Modification of the plan based on comments of the review board

Implementation of the program

Yearly report and analysis of outcome variables

To guide the implementation of the activities outlined above, the committee has provided specific advice on several components, including an approach to evaluating malaria problems and designing control strategies (the paradigm approach), program management, monitoring and evaluation, and operational research.

Paradigm Approach

Given the complex and variable nature of malaria, the committee believes that the epidemiologic paradigms (see Chapter 10 ), developed in conjunction with this study, may form the basis of a logical and reasoned approach for defining the malaria problems and improving the design and management of malaria control programs.

The committee recommends that the paradigm approach be field tested to determine its use in helping policymakers and malaria program managers design and implement epidemiologically appropriate and cost-effective control initiatives.

The committee recognizes that various factors, including the local ecology, the dynamics of mosquito transmission of malaria parasites, genetically determined resistance to malaria infection, and patterns of drug use, affect patterns of malaria endemicity in human populations and need to be considered when malaria control strategies are developed. In most endemic countries, efforts to understand malaria transmission through field studies of vector populations are either nonexistent or so limited in scope that they have minimal impact on subsequent malaria control efforts. The committee recognizes that current approaches to malaria control are clearly inadequate. The committee believes, however, that malaria control strategies are sometimes applied inappropriately, with little regard to the underlying differences in the epidemiology of the disease.

The committee recommends that support for malaria control programs include funds to permit a reassessment and optimization of antimalarial tools based on relevant analyses of local epidemiologic, parasitologic, entomologic, socioeconomic, and behavioral determinants of malaria and the costs of malaria control.

Poor management has contributed to the failure of many malaria control programs. Among the reasons are a chronic shortage of trained managers who can think innovatively about health care delivery and who can plan, implement, supervise, and evaluate malaria control programs. Lack of incentives, the absence of career advancement options, and designation of responsibility without authority often hinder the effectiveness of the small cadre of professional managers that does exist. The committee recognizes that management technology is a valuable resource that has yet to be effectively introduced into the planning, implementation, and evaluation of most malaria control programs.

The committee recommends that funding agencies utilize management experts to develop a comprehensive series of recommendations and guidelines as to how basic management skills and technology can be introduced into the planning, implementation, and evaluation of malaria control programs.

The committee recommends that U.S. funding of each malaria control program include support for a senior manager who has responsibility for planning and coordinating malaria control activities. Where such an individual does not exist, a priority of the control effort should be to identify and support a qualified candidate. The manager should be supported actively by a multidisciplinary core group with expertise in epidemiology, entomology, the social sciences, clinical medicine, environmental issues, and vector control operations.

Monitoring and Evaluation

Monitoring and evaluation are essential components of any control program. For malaria control, it is not acceptable to continue pursuing a specific control strategy without clear evidence that it is effective and reaching established objectives.

The committee recommends that support for malaria control programs include funds to evaluate the impact of control efforts on the magnitude of the problem and that each program be modified as necessary on the basis of periodic assessments of its costs and effectiveness.

Problem Solving (Operational Research) and Evaluation

At the outset of any malaria prevention or control initiative and during the course of implementation, gaps in knowledge will be identified and problems will arise. These matters should be addressed through clearly defined, short-term, focused studies. Perhaps the most difficult aspects of operational research are to identify the relevant problem, formulate the appropriate question, and design a study to answer that question.

The committee recommends that a problem-solving (operational research) component be built into all existing and future U.S.-funded malaria control initiatives and that support be given to enhance the capacity to perform such research. This effort will include consistent support in the design of focused projects that can provide applicable results, analysis of data, and dissemination of conclusions.

The committee concludes that there is a need for additional scientists actively involved in malaria-related research in the United States and abroad. To meet this need, both short- and long-term training at the doctoral and postdoctoral levels must be provided. This training will be of little value unless there is adequate long-term research funding to support the career development of professionals in the field of malaria.

The committee recommends support for research training in malaria.

Whereas the curricula for advanced degree training in basic science research and epidemiology are fairly well defined, two areas require attention, especially in the developing world: social sciences and health management and training.

The committee recommends that support be given for the development of advanced-degree curricula in the social sciences, and in health management and training, for use in universities in developing and developed countries.

The availability of well-trained managers, decision makers, and technical staff is critical to the implementation of any malaria prevention and control program. The development of such key personnel requires a long term combination of formal training, focused short courses, and a gradual progression of expertise.

The committee recommends support for training in management, epidemiology, entomology, social sciences, and vector control. Such training for malaria control may be accomplished through U.S.-funded grant programs for long-term cooperative relationships

between institutions in developed and developing countries; through the encouragement of both formal and informal linkages among malaria-endemic countries; through the use of existing training courses; and through the development of specific training courses.

The committee recommends further that malaria endemic countries be supported in the development of personnel programs that provide long-term career tracks for managers, decision makers, and technical staff, and that offer professional fulfillment, security, and competitive financial compensation.

Malaria is making a dramatic comeback in the world. The disease is the foremost health challenge in Africa south of the Sahara, and people traveling to malarious areas are at increased risk of malaria-related sickness and death.

This book examines the prospects for bringing malaria under control, with specific recommendations for U.S. policy, directions for research and program funding, and appropriate roles for federal and international agencies and the medical and public health communities.

The volume reports on the current status of malaria research, prevention, and control efforts worldwide. The authors present study results and commentary on the:

• Nature, clinical manifestations, diagnosis, and epidemiology of malaria.
• Biology of the malaria parasite and its vector.
• Prospects for developing malaria vaccines and improved treatments.
• Economic, social, and behavioral factors in malaria control.

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Malaria is a mosquito-borne infectious disease caused by the bite of female Anopheles mosquitoes, which spread infectious Plasmodium parasites into a host. Traditional malaria symptoms include fever, chills, headache, muscle aches and fatigue. Nausea, vomiting and diarrhea also are common. Untreated malaria can lead to severe disease, kidney failure and death. Neurological complications can occur in severe cases, most commonly in young children.

Most malaria cases occur during rainy periods in endemic regions. The World Health Organization estimates that in 2020 , globally about 240 million people had malaria and about 627,000 of them died. A disproportionate burden of malarial disease occurs in Sub-Saharan Africa, where children under age 5 account for about 80% of all malaria deaths.

A vaccine to prevent malaria is available; however, its variable efficacy underscores the need for new interventions that offer high-level protection against disease. Malaria is a research priority at NIAID, which is the lead U.S. government agency investigating the disease. Scientists are researching improved vaccines and preventive interventions as well as mosquito control techniques, easy-to-use diagnostics, and improved therapies as parasites continue to develop resistance to currently available antimalarials.

News Releases

• Experimental NIH Malaria Monoclonal Antibody Protective in Malian Children April 26, 2024
• NIAID Marks World Malaria Day April 25, 2023
• Monoclonal Antibody Prevents Malaria Infection in African Adults October 31, 2022

See all Malaria related news releases

NIAID Now Blog

• The Hidden Link Between Malaria and Lupus July 5, 2024
• NIAID Raises Awareness to Malaria-like Diseases in W. Africa June 6, 2024
• NIAID Commemorates World Malaria Day 2024 April 25, 2024

See all Malaria related NIAID Now posts

Related Public Health and Government Information

To learn about risk factors for malaria and current prevention and treatment strategies visit the MedlinePlus malaria site .

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Patterns and predictors of malaria among head porters: a mobile population in Ghana

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Lifestyles associated with malaria in pregnancy in northwest Colombia: a mixed study from Latin American critical epidemiology

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Malaria and typhoid fever co-infection: a retrospective analysis of University Hospital records in Nigeria

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Evidence on sulfadoxine-pyrimethamine resistance molecular markers from India: interpret with caution

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Quinine, an old anti-malarial drug in a modern world: role in the treatment of malaria

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Effectiveness of plant-based repellents against different Anopheles species: a systematic review

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Foul wind, spirits and witchcraft: illness conceptions and health-seeking behaviour for malaria in the Gambia

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malaria summary

malaria , A serious relapsing infection caused by protozoa of the genus Plasmodium ( see plasmodium), transmitted by the bite of the Anopheles mosquito . Known since before the 5th century bc , it occurs in tropical and subtropical regions near swamps. The roles of the mosquito and the parasite were proved in the early 20th century. Annual cases worldwide are estimated at 250 million and deaths at 2 million. Malaria from different Plasmodium species differs in severity, mortality, and geographic distribution. The parasites have an extremely complex life cycle; in one stage they develop synchronously inside red blood cells. Their mass fissions at 48- or 72-hour intervals cause attacks lasting 4–10 hours. Shaking and chills are followed by fever of up to 105 °F (40.6 °C), with severe headache and then profuse sweating as temperature returns to normal. Patients often have anemia, spleen enlargement, and general weakness. Complications can be fatal. Malaria is diagnosed by detecting the parasites in blood. Quinine was long used to alleviate the fevers. Synthetic drugs, such as chloroquine, destroy the parasites in blood cells, but many strains are now resistant. Carriers of a gene for a hemoglobinopathy have natural resistance. Malaria prevention requires preventing mosquito bites: eliminating mosquito breeding places and using insecticides or natural predators, window screens, netting, and insect repellent. See also protozoal disease.

The deadly disease transmitted by mosquitoes is one of the leading causes of death in children. How did we eliminate the disease in some world regions and how can we continue progress against malaria?

By: Max Roser and Hannah Ritchie

This article was first published in November 2015, and last revised in February 2024.

Malaria is a disease that is spread between people via infected mosquitoes. The bite of an infected Anopheles mosquito transmits a Plasmodium parasite that enters the victim’s blood and travels into the person’s liver, where it reproduces. The parasites then travel through the bloodstream and enter red blood cells, where they rapidly reproduce and burst red blood cells open; this repeats in cycles, leading to cycles of high fevers with shaking chills, and pain. In the worst cases, malaria leads to coma and death.

The parasites are single-celled microorganisms of the Plasmodium group. Plasmodium falciparum is the most lethal in humans, and responsible for most deaths.

Over half a million people died from the disease each year in the 2010s. Most were children, and the disease is one of the leading causes of child mortality .

For an overview of malaria — and how we can make progress against it — you can read the following essay:

Malaria: One of the leading causes of child deaths, but progress is possible and you can contribute to it

We do not have to live in a world in which 1320 children die from a preventable disease every day.

See all interactive charts on malaria ↓

Malaria deaths

In the visualizations we provide estimates of the total number of deaths from the World Health Organization (WHO) from 2000 onwards, and the Institute of Health Metrics and Evaluation (IHME), Global Burden of Disease (GBD) from 1990 onwards.

These estimates are notably different across various countries which affects the total number of reported deaths. IHME figures, as shown, tend to be higher.

Malaria death estimates from WHO

The WHO has published estimates of the global number of people who die from malaria since 2000. This is shown in the chart.

The WHO estimates that the global death toll fell steadily between 2000 and 2015. Since then, progress has slowed. The number of deaths increased in 2020 as a result of disruptions during the COVID-19 pandemic . 1

Africa is the world region that is most affected by malaria. In recent years, the vast majority of deaths from malaria occurred on the African continent. But Africa is also the world region that has achieved most progress.

Malaria death estimates from IHME

The Institute of Health Metrics and Evaluation (IHME) has published estimates of the global number of people who die from malaria since 1990. This is shown in the chart.

The IHME estimates a rise, peak and fall between 1990 and 2017.

These estimates are notably higher than those of the WHO. Although divergent on the total number of malaria deaths, both the IHME and WHO estimate that the vast majority of deaths are in the African region.

Malaria deaths by age group

The chart below breaks down the annual number of deaths by age group.

These figures are those published by the IHME’s Global Burden of Disease study — the WHO does not publish country-level data on malaria deaths by age. Note that you can view these trends for any country in the chart.

It shows that the most vulnerable age group to malaria deaths are children under five years old.

Malaria death rates

The visualization shows the age-standardized death rate from malaria, measured as the death rate per 100,000 people in the population.

New cases of malaria

The map shows the number of new cases of malaria per 100,000 people across the world. As the chart shows, malaria cases are most common in the central part of Africa north and south of the equator.

The history of malaria

Humanity’s fight against malaria has a history of many thousand years. 2

For most of that time, humanity was exposed to the disease without any defense.

Malaria’s mark on the human body

The history of humanity is so closely entangled with the history of malaria that the disease left its mark on our bodies.

Sickle cell disorder is one of these marks. It is a genetic condition that deforms red blood cells to be sickle-shaped. Carriers suffer from attacks of pain from a young age and their lives are cut short by the condition. Tens of thousands of people globally die from the disease each year. 3

Why would such a genetic mutation not die out? The reason for the continued existence is that sickle cell disorder hinders the malaria parasite from reproducing, which means people who are carriers of the mutation — with one out of two mutations for it — have a protective advantage in environments where malaria exists.

The prevalence of sickle cell disorder today is a testament to the high-malaria environments in our species’ history. 4

Malaria’s mark on history

Malaria did not only leave its mark on our bodies, but in many ways also on our history. Malaria is thought to have been a secret ally that helped the Germanic and other tribes bring about the downfall of Rome.

By examining the teeth and bones of the Romans, archaeologists have brought together more and more evidence that the mosquito-borne fever once thrived in the warm, marshy river valleys of the Tiber and the Po in the Roman empire. The disease enfeebled the mightiest army of the ancient world directly through epidemics and indirectly by reducing the productivity in the agricultural sector and hastened the fall of Rome. 5

This disease that was powerful enough to afflict the mightiest armies also left its mark on the fate of societies and the lives of many other regions of the world. 6

Malaria’s mark on our drinks

One of the first treatments people discovered against malaria was quinine, which came from an extract from the bark of the cinchona tree in South America. 7

Quinine powder was either drunk with wine or dissolved in water, a mixture that became known as “tonic water”. But quinine is so bitter that tonic water, with concentrations high enough to be effective against malaria, was unpleasant to drink. The British colonial officers stationed in malarious India therefore started to add sugar, lime, and gin to it, and thereby created a drink that is still popular today: gin and tonic.

Malaria was common across half the world — since then it has been eliminated in many regions

Malaria left its mark on our history, our bodies, our drinks, and for thousands of years, caused the deaths of people all around the world.

But in the last few generations, humanity gained ground in this long-lasting battle against the disease. The map shows in which regions of the world malaria is prevalent today (in purple) and where it was prevalent in the past.

Just a few generations ago malaria was common in many more places around the world than it is today. Over the 20 th century, the disease was eliminated in many populous regions of the world, saving the lives of millions.

What the map makes clear is that malaria is not a tropical disease, but a disease that was eliminated everywhere except for the tropics.

Historically, malaria was prevalent in Europe and North America — the poet Friedrich Schiller contracted the disease in Mannheim, Oliver Cromwell in Ireland, and Abraham Lincoln in Illinois. 9

Since then the disease has been eliminated not only there, but also in East Asia and Australia and many parts in the Caribbean, South America, and Africa.

The researchers estimate that historically — and up to around 1900 — our ancestors were at risk from malaria across about half of the world’s land surface. By 2002, the area where humans are at risk of malaria contracted to a quarter (27%). 8

Why are these parts not malarious anymore?

Three factors were responsible for this global reduction of malarious regions: 10

First, public health measures, especially the widespread use of insecticides to attack the mosquito.

Second, drainage of swampland to expand agricultural land , which had the side effect of restricting breeding grounds for mosquitoes.

Third, social and economic development, which made treatment available to those who were infected, and also led to improvements in housing conditions and mosquito nets, which lowered the chances of infection in the first place.

All three factors — insecticides, land use change, and economic development — were major reasons that Europe and the other regions shown in shades of yellow, orange, and red are free of malaria today.

Malaria in the US

The map is taken from the US census from 1870. It shows in detail what the previous section discussed. Shown is the share of all deaths caused by malaria in the American Southeast at that time.

Malaria was very prevalent in this region in the past. Particularly along the coasts and along the Mississippi, malaria killed many Americans.

How can the world continue to make progress against malaria?

The world has already been very successful against this disease which is one of the deadliest diseases in humanity's history. How was this possible and what can we do to continue this progress?

Insecticide-treated bednets

The world is making progress against malaria thanks to insecticide-treated bednets.

Even after a century of progress against malaria, the disease remains devastating for millions. The World Health Organization estimates that 216 million suffered from the disease in 2016. 12

Fortunately, only a small fraction of malaria victims die of the disease. But those who die are the very weakest; three out of four malaria victims are children younger than 5 years old making it one of the leading causes of child mortality in the world today. 13

The world is making progress against malaria

One line of humanity’s attack on malaria is to progressively reduce the area in which malaria is prevalent. Another one is to prevent the transmission of the parasite in regions where it is still prevalent. It is a surprisingly simple technology that stopped transmission and saved the lives of millions in the last few years alone.

The years since the turn of the millennium were an extraordinarily successful era in the fight against malaria. The two maps show the change in malaria mortality for children in the region where the disease causes the highest death toll. 14

One of the most important contributors to the decline was the increased distribution of insecticide-treated bed nets.

Bed nets protect those who sleep under them, and the insecticide used on the bed nets kills the mosquitoes. So a community where a sufficiently high number of people sleep under bed nets the entire community is protected, regardless of whether they use the bed nets themselves. This is similar to the positive externality effect that vaccination has on communities.

Two other interventions that were important for the reduction in the disease burden of malaria were indoor residual spraying (IRS) of insecticides, and the treatment of malaria patients with artemisinin-based combination therapy (ACT).

Read more in our article:

Vaccines against malaria

Charles Alphonse Laveran discovered in 1880 that the Plasmodium parasite was the cause of malaria. 15 But all earlier attempts to develop vaccines were unsuccessful. Malaria vaccines such as SPf66 were insufficiently effective and until recently none of the scientific efforts led to a licensed vaccine. 16

This has changed with the malaria vaccine RTS,S , the world's first licensed malaria vaccine, which has been recommended for use by the WHO since 2021. The vaccine is undergoing pilot trials in select countries and it is hoped to protect against the parasite in the future. 17 Since then, another malaria vaccine has also been developed — the R21/Matrix-M vaccine, which has been recommended for use since 2023.

Malaria and economic prosperity

There are high economic costs of malaria.

Malaria was once prevalent in many of today's richest countries, but it was eliminated there over the last century. Today, malaria still affects some of the poorest countries in the world, as the chart shows.

This is partly because the poor finances make it hard to fight the disease, but also because the disease lowers the productivity of the economy.

In the chart below, you can see each country’s prevalence of malaria compared to their GDP per capita.

Interactive charts on malaria

World Malaria Report 2021 . Geneva: World Health Organization; 2021.

Wiesenfeld SL (1967) — Sickle-cell trait in human biological and cultural evolution. Science. 157:1134–40. Joy DA, Feng XR, Mu JB, et al. (2003) — Early origin and recent expansion of Plasmodium falciparum. Science. 300:318–21.

The Institute for Health Metrics and Evaluation’s 2019 Global Burden of Disease study estimated that around 40,000 people died from sickle cell disorder in 2019. Results are online here: https://vizhub.healthdata.org/gbd-compare/

See: Aidoo M, Terlouw DJ, Kolczak MS, McElroy PD, ter Kuile FO, Kariuki S, Nahlen BL, Lal AA, Udhayakumar V. (2002) — Protective Effects of the Sickle Cell Gene Against Malaria Morbidity and Mortality. In Lancet 2002; 359:1311-1312.

See Robert Sallares (2001) — Malaria and Rome: A History of Malaria in Ancient Italy and Robert Sallares, Abigail Bouwman and Cecilia Anderung (2012) — The Spread of Malaria to Southern Europe in Antiquity: New Approaches to Old Problems. Online here .

Daron Acemoglu, Simon Johnson, James A. Robinson (2002) — Reversal of Fortune: Geography and Institutions in the Making of the Modern World Income Distribution. In The Quarterly Journal of Economics, Vol. 117, No. 4 (Nov., 2002), pp. 1231-1294. Online here: ttps://economics.mit.edu/files/4127 John Luke Gallup and Jeffrey D. Sachs (2001) — The Economic Burden of Malaria https://www.ncbi.nlm.nih.gov/books/NBK2624/

On the history of the first effective treatments see Kennedy — A Brief History of Disease, Science and Medicine.

The original map was published in Simon I Hay, Carlos A Guerra, Andrew J Tatem, Abdisalan M Noor, and Robert W Snow (2004) — The global distribution and population at risk of malaria: past, present, and future. In The Lancet Infectious Diseases 2004 June; 4(6): 327–336. DOI: 10.1016/S1473-3099(04)01043-6. https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(04)01043-6/fulltext I have digitized the Figure 1 using image tracing in Adobe Illustrator. The historical mapping of the prevalence of malaria is based on the pioneering work of Lysenko in the 1960s: Lysenko AJ, Semashko IN. Geography of malaria (1968) — A medico-geographic profile of an ancient disease. In: Lebedew AW, editor. Itogi Nauki: Medicinskaja Geografija. Academy of Sciences, USSR; Moscow: 1968. pp. 25–146. Lysenko AJ, Beljaev AE (1969) — An analysis of the geographical distribution of Plasmodium ovale. Bull World Health Organization; 40:383–94.

On the cause of Oliver Cromwell’s death see the FAQs at OliverCromwell.org , on Friedrich Schiller see Bayerischer Rundfunk here , on Abraham Lincoln see " The Physical Lincoln ". Other famous victims — although it is not always possible to diagnose the disease of historical figures — were German painter Albrecht Dürer, who contracted the disease in the Netherlands, and several popes, who died of the disease as malaria was very prevalent in Italy until recently.

See Hay et al (2004) above and de Zulueta J. (1994) — Malaria and ecosystems: from prehistory to posteradication. In Parassitologia. 1994 August. 36(1-2):7-15. World Bank (2009) — World Development Report (2009) - Part I: Reshaping Economic Geography. Washington, DC: World Bank. Online here .

This is taken from the Statistical Atlas from the 9th Census of the United States 1870 (published 1874). All maps and charts from the Statistical Atlas from the 9th Census of the United States 1870 are online at Radical Cartography here . This map shown here is available in high-resolution here .

Figures for 2016 according to the WHO: http://www.who.int/malaria/en/

The age-specific mortality figures are those published by the IHME’s Global Burden of Disease [the WHO does not publish country-level data on malaria deaths by age]. The share of children younger than 5 among malaria victims fell slightly over the course of the last generation, from 79% in 1990 to 72% in 2015. Here is the data: https://ourworldindata.org/grapher/malaria-deaths-by-age?stackMode=relative

Both the WHO and the IHME report a strong decline of malaria deaths since 2000. But throughout this period the IHME consistently estimates the number of annual deaths to be higher.

See Francis EG Cox (2010) — History of the discovery of the malaria parasites and their vectors. In Parasites and Vectors. Online here.

For an overview see Adrian V. S. Hill (2011) — Vaccines against malaria. In Philos Trans R Soc Lond B Biol Sci. 2011 Oct 12; 366(1579): 2806–2814. doi: 10.1098/rstb.2011.0091.

See RTS,S Clinical Trials Partnership (2015) — Efficacy and safety of RTS,S/AS01 malaria vaccine with or without a booster dose in infants and children in Africa: final results of a phase 3, individually randomised, controlled trial. In The Lancet, Volume 386, ISSUE 9988, P31-45, July 04, 2015. Online here .

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• How It Spreads
• Where Malaria Occurs
• World Malaria Day 2024
• Clinical Guidance: Malaria Diagnosis & Treatment in the U.S.
• Clinical Features
• Clinical Testing and Diagnosis
• Malaria Risk Assessment for Travelers
• Choosing a Drug to Prevent Malaria
• Malaria Surveillance, United States 2019 – 2020
• How to Report a Case of Malaria
• Public Health Strategy
• Malaria's Impact Worldwide
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Malaria Surveillance, United States 2019 – 2020

What to know.

United States malaria surveillance data guides public health actions for preparedness, prevention, detection, and response at the patient, state, and federal levels. In 2019, 2,048 confirmed malaria cases were reported to the CDC National Malaria Surveillance System. Due to substantial reductions in foreign travel as a consequence of the COVID-19 pandemic, 602 malaria cases were reported to the CDC in 2020. Almost all cases reported in 2019 and 2020 were imported, or travel associated.

Malaria surveillance in the United States and its territories provides information on its occurrence (e.g., temporal, geographic, and demographic), informs recommendations for preventing malaria among travelers and guidelines for treating malaria patients, and facilitates rapid implementation of transmission control measures if locally acquired cases are identified.

Surveillance Methods

Malaria is nationally notifiable, and cases are reported directly from health departments, jurisdictions, and territories to the CDC program that implements the National Malaria Surveillance System (NMSS) as one of the diseases included in the National Notifiable Diseases Surveillance System ( NNDSS ).

As a notifiable condition, positive malaria laboratory test results are automatically reported from hospital, commercial, public health, and other laboratories to state and local health departments through the electronic laboratory reporting system . The electronic laboratory reports prompt investigations by state and local health departments, then case reports are submitted to CDC. Both systems rely on passive reporting from the jurisdictions, and the number of cases might differ, especially because of differences in date classifications. NNDSS report dates might be assigned according to the date of diagnosis, or the date reported to the health department, and NMSS assigns dates according to illness onset. This report summarizes data from the integration of all NMSS and NNDSS cases after deduplication and reconciliation. This activity was reviewed by CDC and was conducted consistent with applicable federal law and CDC policy. 1

Confirmed or suspected malaria in the United States is defined by the Council of State and Territorial Epidemiologists (CSTE) and CDC case definition . Malaria Surveillance and Case Investigation Best Practices, including resources on the malaria case definitions are available at the CDC website .

Data elements reported and analyzed include age, sex, pregnancy status, residence, illness onset date, laboratory results, travel history (countries, regions, and dates), chemoprophylaxis (medication used and adherence), history of malaria (date and species), blood transfusion or organ transplant history, hospitalization, clinical complications, treatment medications, illness outcome (survived versus died), and case classification. Data elements with missing values were excluded from analysis.

1 45 C.F.R. part 46.102(l)(2), 21 C.F.R. part 56; 42 U.S.C. §241(d); 5 U.S.C. §552a; 44 U.S.C. §3501 et seq.

Key findings

• There were 2,048 confirmed malaria cases in 2019, compared to 1,823 confirmed cases reported in 2018. In 2020 there were 602 confirmed malaria cases reported, the lowest number since 1972.
• There were more U.S. civilian cases in 2019 compared to 2018. Compared to 2019, in 2020 there were fewer cases across all residence categories.
• For 2019 and 2020, the most common demographic characteristics among reported cases were males, those aged 18 – 64 years, non-Hispanic ethnicity, and Black/African American race.
• In 2019 and 2020, Africa is the primary region of acquisition for travel-associated U.S. malaria cases, and cumulatively, more than half of all cases during these years were acquired from West Africa. In 2019 and 2020, ≤6% of cases were acquired from Asia, and 1% or fewer cases were acquired in South America, Central America and the Caribbean, the Middle East, and Oceania.
• Among U.S. civilians, malaria cases reported visiting friends and relatives as the primary reason for travel in both years, followed by business travel.
• Plasmodium falciparum  (85.5% in 2019 and 77.2% in 2020) is the most common species diagnosed among the malaria cases with a species determination, followed by  Plasmodium vivax  (6.0% in 2019 and 12.1% in 2020) and  Plasmodium ovale  (4.9% in 2019 and 6.2% in 2020).
• Thirteen states/jurisdictions in 2019 and twelve states/jurisdictions in 2020 were in the top quartile for having the most malaria cases. Eleven states/jurisdictions were in the top quartile for both years, and include New York City, Maryland, Texas, California, Pennsylvania, Virginia, New Jersey, Minnesota, North Carolina, Florida, and Ohio

What is CDC doing?

• CDC supports U.S. states, territories, and jurisdiction health departments in the investigation, response and reporting of malaria cases.
• CDC provides  resources  to health care providers in the United States including diagnosis and treatment guidelines and a 24/7/365 malaria hotline for clinicians and state and local health department staff.

Number of malaria cases by species and year, 2014 – 2020

For years 2014 – 2020, P. falciparum is the predominant species of malaria diagnosed in the United States, followed by P. vivax . The highest proportion of P. falciparum observed over this period occurred in 2019. 2020 had the lowest proportion of P. falciparum during this period. The proportion of the relapsing species ( P. vivax and P. ovale ) was higher in 2020 than in 2019.

Number of malaria cases by demographics, region of acquisition, and primary reason for travel, by patient resident status — United States, 2019

In 2019, most people diagnosed with malaria in the United States were male, 18 – 64 years old, non-Hispanic or Latino ethnicity, and Black/African American race. Case patients predominantly traveled to Africa. More than half of all case patients traveled to or from West Africa. More than two thirds of U.S. civilians with malaria traveled to visit friends and relatives in 2019.

Number of malaria cases by demographics, region of acquisition, and primary reason for travel, by patient resident status — United States, 2020

In 2020, most people diagnosed with malaria in the United States were male, 18 – 64 years old, non-Hispanic or Latino ethnicity, and Black/African American race. Case patients predominantly traveled to Africa. More than half of all case patients traveled to or from West Africa.  More than half of U.S. civilians with malaria traveled to visit friends and relatives in 2020.

The stacked bar graph shows the number of cases by illness onset month. The species determination for each case is colored ( P. falciparum in blue, P. vivax and P. ovale in orange, and other or unknown species in green). In 2019, the lowest number of cases had illness onset in February through April; the highest number of cases were in July through September. In 2020, the lowest number of malaria cases were in April through June 2020. The highest number of malaria cases had illness onset in January 2020. In both years, Plasmodium falciparum made up the highest proportion of cases. Compared to 2019, in 2020 the proportion of P. vivax and P. ovale species was higher.

Supplementary data files

Downloadable data files‎.

• Mace KE, Lucchi NW, Tan KR. Malaria Surveillance — United States, 2018. MMWR Surveill Summ 2022;71(No. SS-8):1–29. DOI: http://dx.doi.org/10.15585/mmwr.ss7108a1 .
• Electronic Laboratory Reporting (ELR) | Electronic Laboratory Reporting (ELR) | CDC
• Clinical Guidance: Malaria Diagnosis & Treatment in the U.S. | Malaria | CDC
• How NNDSS Conducts Case Surveillance | CDC
• Criteria for defining a case of malaria https://cdn.ymaws.com/www.cste.org/resource/resmgr/PS/13-ID-08.pdf
• Morbidity and Mortality Weekly Report , Vol. 29, No. 34 (August 29, 1980), pp. 413-415

Malaria is a serious disease caused by a parasite that infects the Anopheles mosquito. You get malaria when bitten by an infective mosquito.

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The unintended consequences of success against malaria

by North Carolina State University

For decades, insecticide-treated bed nets and indoor insecticide spraying regimens have been important—and widely successful—treatments against mosquitoes that transmit malaria, a dangerous global disease. Yet for a time, these treatments also suppressed undesirable household insects like bed bugs, cockroaches and flies.

Now, a new North Carolina State University study reviewing the academic literature on indoor pest control shows that as the household insects developed resistance to the insecticides targeting mosquitoes, the return of these bed bugs, cockroaches and flies into homes has led to community distrust and often abandonment of these treatments—and to rising rates of malaria.

The work appears in Proceedings of the Royal Society B: Biological Sciences .

In short, the bed nets and insecticide treatments that were so effective in preventing mosquito bites —and therefore malaria—are increasingly viewed as the causes of household pest resurgence.

"These insecticide-treated bed nets were not intended to kill household pests like bed bugs, but they were really good at it," said Chris Hayes, an NC State Ph.D. student and co-corresponding author of a paper describing the work. "It's what people really liked, but the insecticides are not working as effectively on household pests anymore."

"Non-target effects are usually harmful, but in this case they were beneficial," said Coby Schal, Blanton J. Whitmire Distinguished Professor of Entomology at NC State and co-corresponding author of the paper.

"The value to people wasn't necessarily in reducing malaria, but was in killing other pests," Hayes added. "There's probably a link between use of these nets and widespread insecticide resistance in these house pests, at least in Africa."

The researchers add that other factors—famine, war, the rural/city divide, and population displacement, for example—also could contribute to rising rates of malaria.

To produce the review, Hayes combed through the academic literature to find research on indoor pests like bed bugs, cockroaches and fleas, as well as papers on malaria, bed nets, pesticides and indoor pest control. The search yielded more than 1,200 papers, which—after an exhaustive review process—were whittled down to a final count of 28 peer-reviewed papers fulfilling the necessary criteria.

One paper—a 2022 survey of 1,000 households in Botswana—found that while 58% were most concerned with mosquitoes in homes, more than 40% were most concerned with cockroaches and flies.

Hayes said a recent paper—published after this NC State review was concluded—showed that people blamed the presence of bed bugs on bed nets.

"There is some evidence that people stop using bed nets when they don't control pests," Hayes said.

The researchers say that all hope is not lost, though.

"There are, ideally, two routes," Schal said. "One would be a two-pronged approach with both mosquito treatment and a separate urban pest management treatment that targets pests. The other would be the discovery of new malaria -control tools that also target these household pests at the same time. For example, the bottom portion of a bed net could be a different chemistry that targets cockroaches and bed bugs .

"If you offer something in bed nets that suppresses pests, you might reduce the vilification of bed nets."

Journal information: Proceedings of the Royal Society B

Provided by North Carolina State University

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• Published: 20 July 2024

Influence of environmental, geographic, socio-demographic, and epidemiological factors on presence of malaria at the community level in two continents

• Oswaldo C. Villena 1 ,
• Ali Arab 2 ,
• Catherine A. Lippi 3 , 4 ,
• Sadie J. Ryan 3 , 4 , 5 &
• Leah R. Johnson 6 , 7 , 8  

Scientific Reports volume  14 , Article number:  16734 ( 2024 ) Cite this article

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• Climate sciences
• Computational biology and bioinformatics
• Environmental sciences

The interactions of environmental, geographic, socio-demographic, and epidemiological factors in shaping mosquito-borne disease transmission dynamics are complex and changeable, influencing the abundance and distribution of vectors and the pathogens they transmit. In this study, 27 years of cross-sectional malaria survey data (1990–2017) were used to examine the effects of these factors on Plasmodium falciparum and Plasmodium vivax malaria presence at the community level in Africa and Asia. Monthly long-term, open-source data for each factor were compiled and analyzed using generalized linear models and classification and regression trees. Both temperature and precipitation exhibited unimodal relationships with malaria, with a positive effect up to a point after which a negative effect was observed as temperature and precipitation increased. Overall decline in malaria from 2000 to 2012 was well captured by the models, as was the resurgence after that. The models also indicated higher malaria in regions with lower economic and development indicators. Malaria is driven by a combination of environmental, geographic, socioeconomic, and epidemiological factors, and in this study, we demonstrated two approaches to capturing this complexity of drivers within models. Identifying these key drivers, and describing their associations with malaria, provides key information to inform planning and prevention strategies and interventions to reduce malaria burden.

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Introduction.

Malaria is the deadliest vector-borne disease worldwide, causing 249 million infections and taking the lives of 608,000 people in 2022 alone 1 . The overwhelming majority (94%) of malaria cases occur in Africa, where Plasmodium falciparum is the most prevalent malaria parasite, accounting for 99.5% of cases versus the 0.5% caused by P. vivax 1 . Asia also has considerable malaria burden, where 50.9% of cases are caused by P. vivax and 49.1% are caused by P. falciparum 2 . Despite a 14-year decline in global malaria cases and deaths following continued intervention efforts, a major resurgence of malaria has occurred worldwide since 2014 1 , 3 , 4 . One of the biggest challenges to reducing malaria burden is understanding the complex interaction of factors that drive and shape malaria transmission dynamics.

Transmission dynamics of mosquito-borne diseases (MBDs), like malaria, can be difficult to describe and predict due to multiple levels of complexity arising from interactions between vectors, pathogens, hosts, and the environment 5 , 6 . Transmission of MBDs is directly impacted by climate, particularly temperature and precipitation, and to a lesser degree humidity and wind patterns 7 , 8 . Yet, there are many other factors that can mediate the spatial and temporal distribution, intensity, and duration of MBDs 5 , 6 , 9 . There is evidence to support that malaria occurrence, transmission, and seasonality are influenced by environmental (e.g., isothermality), socio-economic (e.g., human population density), and health factors (e.g., access to health services) 10 . Yet, the influence of these interacting elements on malaria transmission dynamics is often not well understood, or are highly variable across regions.

The effects of temperature and rainfall on malaria dynamics are probably the most well studied because these two factors are believed to have the greatest direct impact on mosquito-borne diseases 9 . Mosquitoes are ectotherms, and temperature affects their physiology, behavior, and development 11 . Furthermore, temperature also affects the development of Plasmodium parasites inside the mosquito (e.g., the extrinsic incubation period, 12 ). Therefore, malaria transmission dynamics are highly constrained by temperature 11 , 13 , 14 , 15 , 16 . Precipitation and related factors (e.g., evaporation rates, presence of breeding habitat, irrigation, etc.) also play vital roles in MBD transmission dynamics by creating habitats necessary for the aquatic stages of mosquito development 9 , thereby impacting vector abundance and distribution 17 , 18 , 19 .

Although temperature and precipitation are key drivers of MBDs, additional factors affect malaria transmission dynamics, but are less well-studied. These include heterogeneous human population density linked to urbanization, economic development (e.g., measured as gross domestic product per capita, GDPPC, or the human development index, HDI or habitat which can be measured as variables such as normalized difference vegetation index (NDVI) or elevation). For example, prior studies found human population density to be a reliable metric to define patterns of malaria risk, with moderately populated areas typically having high malaria prevalence 20 , 21 . In Africa, malaria was not historically considered a public health problem in urban centers, compared to rural areas, because urbanization is associated with the reduction of suitable breeding habitats and vegetation cover for the primary malaria vectors, Anopheles gambiae , An. arabiensis , An. coluzzii, and An. Funestus 22 , 23 , 24 ] . In contrast, An. stephensi , An. minimus , and An. dirus are the main malaria vectors in southern and western Asia, where urban and coastal malaria outbreaks are more common 24 . However, the recent expansion of An. stephensi from Asia into Africa 25 poses a major potential health risk for densely populated urban areas in Africa, as this malaria vector is well adapted to reproduce in built environments 26 . Changes in temperature and precipitation patterns due to climate change has significant implications for malaria vectors and the transmission dynamics of malaria such as vector survival and development, parasite development, range expansion, length of transmission season, availability of breeding sites, and insecticide resistance, etc. 27 , 28 , 29 .

Poverty is historically associated with malaria since families in areas with lower GDPPC usually have less access to quality housing, health services, and municipal water and sanitation services 30 , 31 . In the past, environmental and socio-economic changes contributed to malaria eradication in the USA and Europe, and improved control in most of Central and South America 32 , 33 . However, the relationship between GDPPC and malaria may be bi-directional: GDPPC could affect malaria prevalence and/or malaria prevalence could affect countries’ GDPPC. Similarly, lower values of HDI are associated with high malaria 34 . Measures of environmental conditions can also serve as predictors of malaria activity. While there is consensus that high malaria prevalence occurs in areas of moderate elevation, the utility of other indicators, like NDVI, can vary across studies 21 . Some studies have found that NDVI is positively associated with mosquito abundance, mosquito community assembly, and malaria cases 35 , 36 . However, other studies found that NDVI is negatively associated with malaria cases 37 . These discrepancies could be due to the differences in the underlying habitat preferences of the mosquitoes, perhaps making NDVI useful in more nuanced modeling applications 37 .

In this study, an integrated modeling framework for evaluating impacts of environmental, geographic, socio-demographic, and epidemiological factors on malaria in Sub-Saharan Africa and Southeast Asia is presented and implemented. Additionally, the association of P. falciparum and P. vivax malaria survey data with the basic reproductive number ( R 0 ), defined as the number of secondary cases that on average an infected individual will cause in a susceptible population, was assessed. To our knowledge, this is the first study to incorporate R 0 as a factor to assess for its association with malaria survey data.

• Malaria survey data

Data on P. falciparum and P. vivax malaria at the community level in 46 countries in Africa and 21 countries in Asia from 1990 to 2017 (Figure S1; supplemental material) were obtained from the Malaria Atlas Project (MAP), https://malariaatlas.org/ 38 , 39 . The survey-data collected by MAP followed the General Data Protection Regulation (GDPR) and associated data protection legislation, https://malariaatlas.org/privacy-policy/ . The survey data is publicly available and consist of the number of individuals at each sampled location (i.e., longitude, latitude) observed to have P. falciparum and P. vivax parasites in their blood, together with the total number of individuals sampled, respectively. Data was aggregated from multiple malaria survey studies which number varies by community, country, and continent. The malaria survey data were converted to presence/absence of malaria at the community level (i.e., 1 was assigned if malaria was present and 0 is malaria was absent). Plasmodium vivax malaria in Africa was not assessed due to insufficient data (718 records of which only 155 showed malaria presence; Table 1 ).

Environmental and geographic variables

Temperature and precipitation.

Monthly temperature and precipitation data from 1990 to 2017 were obtained from the WorldClim Global Climate Data Project using the raster package in R 40 , at a 5-min spatial resolution (17.3 km 2 ). Aggregated mean temperature was calculated for the two quarters (three calendar months) prior to the start month of each survey study (Table 2 ). Isothermality (bio3), a bioclimatic variable from the WorldClim project which quantifies how much day-to-night temperatures oscillate relative to the summer-to-winter annual oscillations, was also considered 41 . Average monthly precipitation (mm) was aggregated to mean precipitation for two quarters prior to the start month of each survey study. Two additional bioclimatic variables were also considered: precipitation of the wettest quarter (bio16), which is the total precipitation for all three months with the highest cumulative precipitation; and the precipitation of the driest quarter (bio17) 40 .

Elevation and normalized difference vegetation index

For topographical data, the Global Multi-resolution Terrain Elevation Data 2010 (GMTED2010) from the U.S. Geological Survey (USGS), with a horizontal grid spacing of 30 arc-seconds (approximately 1 km) was used. Normalized Difference Vegetation Index (NDVI) data, a greenness measure estimating chlorophyll density in vegetation cover, were obtained from the Famine Early Warning Systems Network (FEWS-NET). FEWS-NET NDVI data were generated from the collection of Moderate Resolution Imaging Spectroradiometer (MODIS) instruments flown aboard the Aqua satellite from July 2002 to current times 42 . Real-time and historical NDVI data are composited in 10-day (dekadal) intervals at 250 m spatial resolution 43 . For the studies conducted from 2000 to July 2002, we used MODIS vegetation indices (MOD13A3) collection 6 at 1 km (km) spatial resolution from the EARTHDATA project from USGS and NASA, available from 2000 onward. For malaria survey data prior to 2000, a monthly average NDVI derived from EARTHDATA from 2000 to 2004 was calculated using the “Cell Statistics” function in ArcGIS 10.8.1 44 .

Socio-demographic variables

The socio-demographic variables used were population density, gross domestic product per capita (GDPPC), and the human development index (HDI) at the community level (e.g., where the individual survey studies took place).

Population density was estimated at the site level where malaria surveys occurred. Population density data were obtained from the Gridded Population of the World (GPW) collection from the Global Rural–Urban Mapping Project—(GRUMP) project 45 . We used GRUMP global population density at five-year intervals from 1990 to 2015 (i.e., 1990, 1995, 2000) with a resolution of 30 arc-seconds (1 km). We extracted population density data in intervals of 5 years (e.g., from the 1990 raster data set we extracted approximate population density from 1990 to 1994). Due to high variability in population density across survey study locations, in our models, we scaled population density using the “scale” function in R 46 where the vector mean is subtracted from each x i value and divided by the standard deviation of the vector.

Gross Domestic Product per capita (GDPPC) and HDI data from 1990 to 2015 were obtained from the Gridded Global Datasets 47 . The GDPPC data indicate the purchasing power parity in constant 2011 international US dollars. The HDI data represent key aspects of development, namely life expectancy, education expressed as years of schooling, and per capita income indicators. The GDPPC and the HDI data are available at the sub-national level for the whole world at 5 arc-min resolution and WGS84 projection 47 . GDPPC and HDI data were in the form of network common data form (NetCDF), which were converted to raster using the “Make NetCDF Raster Layer” tool from ArcGIS 10.8.1.

The raster data sets (i.e., temperature, precipitation, elevation, NDVI, population density, GDPPC, HDI) which spans different spatial and temporal resolutions were imported into ArcGIS version 10.8.1 and resampled if needed and synchronized to the timing of the response variable. We resampled the raster datasets using either the nearest method for variables like NDVI or the bilinear method for layers with continuous data 48 , 49 . Next, data for each survey study site was extracted using geographic coordinates (latitude and longitude) as a merging points employing the “extract values to points” tool from the spatial analysis toolset in ArcMap 50 . For NDVI, we used bilinear interpolation which means that the value of the cell was calculated from the adjacent cells 51 .

Epidemiological component

The basic reproductive number R 0 of each malaria species (i.e., P. falciparum ) and region (i.e., Africa) was also used as a predictor variable. R 0 , the average number of secondary cases that one infected individual generates during an infectious period in a susceptible population, was estimated for each Anopheles -pathogen pairing in a previous study by Villena et al. 15 . They used the most common parameterization of R 0 for vector-borne infections which is based on the Ross-MacDonald model of malaria transmission 52 . More specifically, they incorporated multiple temperature dependent mosquito and parasite traits 11 , 13 , 14 , 53 into the following equation:

where a is the mosquito biting rate; bc is vector competence, which is a combination of b , the probability of a person becoming infected by a bite of an infected mosquito, and c , the probability of a vector becoming infected by feeding on an infectious person; µ is the mosquito mortality rate; PDR is the parasite development rate; EFD is the mosquito fecundity expressed as the number of eggs per female per day; PEA is the proportion of eggs surviving to adulthood; MDR is the mosquito development rate 15 . All mosquito and malaria parasite traits were obtained under laboratory conditions and at constant temperatures 14 , 15 . R 0 data were matched with aggregated mean temperatures for each of the two quarters prior to the start month of each malaria prevalence study, using temperature as a merging variable. Thus, R 0 , unlike many of the other predictors, corresponds to a study/location in both space and time.

Data analysis with CART and GLMs

Malaria presence/absence data and its relationship to multiple predictors was analyzed (Table 2 ) separately for P. falciparum and P. vivax for Africa and Asia (four subsystems). To do this, two different approaches were used: a classification and regression tree (CART) and a generalized linear model (GLM). The CART approach is a non-parametric statistical model applicable to both numerical and categorical data 54 . A GLM is a flexible generalization of ordinary linear regression that can be used to model data that are not normally distributed 55 , 56 . These two methods are widely used to assess the relationship between a continuous or categorical response variable and predictor variables 57 . Each method has its own advantages and disadvantages. For example, GLMs allow the use of the Bayes Information Criterion (BIC) and stepwise regression to automatically find the “best” model, can have non-linear model specifications, and can handle different response distributions. Some disadvantages of GLMs are the assumptions around the chosen statistical distribution of the response data (which can be restrictive), difficulty in finding a global best model for large predictor dimension, and sensitivity to outliers. Conversely, CART models make few assumptions about the nature of relationships, have no parametric assumptions, and allow for the analysis of many data types (e.g., continuous, binary, ordinal, nominal). Disadvantages of CART models include the lack of variables combinations in each split, potentially unstable tree structures (e.g., change in the sample may give different trees), and focus of optimization at each split (e.g., solutions may not be globally optimal) 57 , 58 .

For the CART approach the rpart function from the rpart (Recursive partioning and regression trees) package was used 59 in R 46 . The rpart function constructs a CART by splitting the dataset and fitting a constant model (here, estimated proportion) within each subset (i.e., at each leaf). Splits are recursive, so that the subsets resulting from a split are further split until a predetermined termination criterion is reached. More specifically, at each step, the split is chosen to occur on the independent variable that results in the largest possible reduction of heterogeneity of the dependent variable, until an impurity state of zero (i.e., the class is homogeneous) or close to zero is reached 60 . The Gini index was used to quantify the level of impurity in our CART model fits, where the Gini index reaches maximum value when all classes in the table have equal probability 60 . The trees generated in this study were built using the following process: first a single variable is found which best splits the data in two groups (i.e., child nodes). The process is then applied separately to each subgroup, and so on recursively until the subgroups either reach a minimum size (100 for these data) or until no improvement can be made.

For the GLM approach, each observation at each location in our dataset was categorized with a binary response variable to indicate whether or not malaria had been observed in sampled individuals in our malaria survey dataset. That is, the response y i,j was defined for the j th individual in location i as

The general logistic GLM is defined by the mean equation:

where η i is the linear predictor, with β 0 as the intercept, β 1 ,…., β n are regression parameters, and x 1 , . . . , x n are the location and time dependent explanatory variables. Observations at data point i, j are then Binomial random variables with “success” probability θ i and sample size N i at each location. We implemented the GLMs using the function glm in R 46 .

A null model, which estimated an intercept only (in effect estimating a single proportion for all sites) was fit, and a full model was also fit including the linear effects of: mean temperature for the two quarters prior to the start of the survey study; mean precipitation for the two quarters prior to the start of the survey study; isothermality (bio3); precipitation of the wettest (BIO 16) and driest (BIO 17) quarter; gross domestic product per capita (GDPPC); the human development index (HDI); population density; the temperature dependent basic reproductive number ( R 0 ) for the two previous quarters of the start of the survey study; year in which the survey study started (year); elevation (elev); and the normalized difference vegetation index (NDVI). A quadratic term for isothermality (BIO 3), temperature, and precipitation was also included in order to capture the non-linear response of these factors.

Next, forward stepwise variable selection was performed using the step function in R 46 to choose a final best fitting model for comparison. Finally, to assess if model assumptions were adequately met, the randomized quantile residuals (RQRs) were computed and plotted, using the statmod package 61 for each of the Null, full, and stepwise chosen models. RQRs are the residuals of choice for GLM models in large dispersion situations 62 .

Model assessment

CART and GLM performance were assessed by estimating the accuracy, precision, recall, and F1-score for each model 63 , 64 , 65 . Model accuracy is defined as the total correctly classified samples divided by the total number of classified samples. Model precision refers to the positive patterns that are correctly predicted from the total number of positive classified samples (true and false positives). Model recall is a measure of the fraction of positive patterns that are correctly classified. The F1-score is the weighted mean of the precision and the recall (See formulas in the section B.1.1; supplemental material) 64 , 66 , 67 . To estimate these performance metrics, the dataset was divided into a training and test dataset, using a stratified random sampling method which divides the dataset into smaller subgroups called strata. Strata are formed based on samples that share attributes or characteristics 68 . Our study dataset was grouped by malaria type ( P. falciparum and P. vivax ), continent, country, and the survey study year, then 70% of the data were randomly divided into the training set and remaining 30% to the testing set.

Plasmodium falciparum malaria in Africa

Figure  1 shows the fitted marginal relationships between P. falciparum malaria in Africa and environmental and bioclimatic factors in the quarter before each survey study period. Additional marginal predictions for earlier quarters are in supplementary material (Figure S2). Marginal predictions for P. falciparum malaria showed qualitatively similar responses for both GLM and CART models (Figs.  1 and 2 ), although the CART model had better accuracy, precision, and F1-score than the GLM (Table S7; supplemental material). For example, the temperature in the quarter prior to the P. falciparum malaria survey study at which presence is predicted to be maximized is 24.9 ° C (GLM model) and 24.8 ° C (CART model), decreasing on either side. The thermal range where predicted malaria presence is non-negligible, is between approximately 12 ° C and 36 ° C for both models (Fig.  1 A). In contrast, marginal predictions for precipitation variables are not as consistent. Precipitation of the prior quarter and P. falciparum malaria showed a positive relationship up to approximately 150 mm of precipitation. After this point, the predicted relationship levels off in the GLM model, but decreases in the CART model (Fig.  1 B). Isothermality (BIO 3) is unusual, showing a potentially higher order nonlinear relationship with P. falciparum malaria presence (e.g., possibly cubic, Fig.  1 E).

Marginal predictions based on particular environmental and bioclimatic predictors for P. falciparum in Africa. ( A ) Temperature 1st quarter prior to the start of the survey study, ( B ) Precipitation 1st quarter prior to the start of the survey study, ( C ) Elevation, ( D ) NDVI, ( E ) Isothermality, ( F ) Precipitation of the wettest quarter, and ( G ) Precipitation of the driest quarter.

Marginal predictions based on socio-demographic and epidemiological predictors for P. falciparum in Africa. ( A ) Year at which the survey study started, ( B ) Gross domestic product per capita, ( C ) Population density, ( D ) Human development index, and ( E ) Basic reproductive number ( R 0) 1st quarter prior to the start of the survey study.

The relationship between socio-demographic and epidemiological factors and P. falciparum malaria in Africa are shown in Fig.  2 . While some predictions of the two models are again similar, they are less consistent than the patterns seen with the environmental predictors. For example, high P. falciparum malaria presence is seen from 1990 to 2000, and both the GLM and CART models capture the constant decline of P. falciparum from 2000 to 2012 well. However, after 2012, the GLM model continues to predict that P. falciparum malaria declines and whereas the CART model showed a resurgence of P. falciparum malaria (Fig.  2 A). This is likely due to the additional flexibility available in the CART model (we only considered up to quadratic terms for the GLM). Predictions for malaria presence with per capita log GDP are similarly disparate between the two models. This may be because these predictors are correlated with each other, and the models separate out the effects of these correlated variables in different ways.

The pruned tree for P. falciparum malaria in Africa from the CART model is given in Supplemental Material (See section A.2), along with the coefficients, standard errors, and P-values from the GLM model (Table S1), a graph of the magnitude and uncertainty of the fitted parameter estimates of each variable of the GLM model (Figure S9), and the graphs for the randomized quantile residuals and the density plot from the GLM Model (Figures S12-A and S12-B).

Plasmodium falciparum malaria in Asia

Figure  3 shows the fitted marginal relationships between P. falciparum malaria in Asia and environmental and bioclimatic factors in the quarter before each survey study period. Results from marginal predictions two quarters prior to the survey study are in the supplementary materials (Figure S3). Similar to P. falciparum malaria in Africa, marginal predictions for P. falciparum malaria in Asia showed similar responses for both GLM and CART (Figs.  3 and 4 ). For example, the normalized difference vegetation index (NDVI) showed a unimodal response: increasing P. falciparum malaria up to a NDVI ∼ 0.53 followed by a decrease (Fig.  3 D). Similarly, Isothermality (BIO 3) is unimodal with a predicted peak in P. falciparum malaria when bio3 is around 62% (Fig.  3 E). In contrast, marginal predictions related to temperature and elevation are not as consistent. The temperature in the quarter prior to the P. falciparum malaria survey study in Asia at which malaria presence is predicted to be maximal is 21 ° C (GLM) and 19.5 ° C (CART) (Fig.  3 A), but the decline at higher temperatures is much less in the GLM than the CART fit. For elevation, the models predict maximum malaria presence when elevation is 752 m (GLM) versus 1,010 m (CART), with malaria decreasing at higher elevations, although again, at different rates (Fig.  3 C).

Marginal predictions based on particular environmental and bioclimatic predictors for P. falciparum in Asia. ( A ) Temperature 1st quarter prior to the start of the survey study, ( B ) Precipitation 1st quarter prior to the start of the survey study, ( C ) Elevation, ( D ) NDVI, ( E ) Isothermality, ( F ) Precipitation of the wettest quarter, and ( G ) Precipitation of the driest quarter.

Marginal predictions based on socio-demographic and epidemiological predictors for P. falciparum in Asia. ( A ) Year at which the survey study started, ( B ) Gross domestic product per capita, ( C ) Population density, ( D ) Human development index, and ( E ) Basic reproductive number ( R 0) 1st quarter prior to the start of the survey study.

In Fig.  4 , the relationship between socio-demographic and epidemiological factors with P. falciparum malaria in Asia are shown. Again, predictions of the two models are similar, except for the predictions by year and the human development index. Similar to P. falciparum malaria predictions in Africa, high P. falciparum malaria from 1990 to 2001 is observed. After that, both the GLM and CART models capture a constant decline of P. falciparum malaria well until 2009 and 2011 for GLM and CART model respectively, then P. falciparum malaria shows a resurgence, although this effect is larger in the GLM (Fig.  4 A). In the GLM model, the relationship between human development index (HDI) and P. falciparum malaria is hump-shaped, with a peak at ∼ 0.44. However, the relationship in the CART model is instead higher order, showing an initial decline in malaria presence up to a HDI ∼ 0.265, then increasing until ∼ 0.49, then decreasing again as the HDI increases further (Fig.  4 D).

The pruned tree for P. falciparum malaria in Asia from the CART model is given in Supplemental Material (See section A.3), along with the coefficients, standard errors, and p-values from the GLM model (Table S2), a graph of the magnitude and uncertainty of the fitted parameter estimates of each variable of the GLM model (Figure S10), and the graphs for the randomized quantile residuals and the density plot from the GLM Model (Figures S12-C and S12-D).

Plasmodium vivax malaria in Asia

Figure  5 shows the fitted marginal relationships between P. vivax malaria in Asia and environmental and bioclimatic factors in the quarter before each survey study period. Additional results for marginal predictions in earlier quarters are in the supplementary materials (Figure S4). The CART model showed better accuracy, recall, and F1-score compared to the GLM model; although the GLM model showed a slightly better precision (Table S10; supplemental material). Similar to the two previous subsystems, both models GLM and CART showed similar trends for predicted P. vivax malaria presence in Asia (Figs.  5 and 6 ). For example, the temperature in the quarter prior to the P. vivax malaria survey study at which malaria presence is predicted to meet maximal is 24 ° C (GLM model) and 24.4 ° C (CART model) and the thermal range where malaria presence is non-negligible, for both models is between approximately 3 ° C and 35 ° C (Fig.  5 A). In contrast, precipitation of the prior quarter showed slightly different peaks in the unimodal relationship with P. vivax malaria, peaking at 150 mm and 200 mm of precipitation for the GLM and CART models respectively (Fig.  5 B). The normalized difference vegetation index (NDVI) is one of the only predicted relationships that is not fully or mostly unimodal in both models. In the GLM model, the relationship between P. vivax malaria presence and NDVI seems to be monotonically increasing, although not with a constant slope, whereas the CART model exhibits a unimodal pattern with a peak at ∼ 0.5 (Fig.  5 D). The precipitation of the wettest quarter (BIO 16) is also different between the two models, with the GLM fit exhibiting a unimodal relationship, but the CART model predicting a similar initial peak, but higher malaria at the wettest locations (Fig.  5 F).

Marginal predictions based on particular environmental and bioclimatic predictors ( A ) Temperature 1st quarter prior to the start of the survey study, ( B ) Precipitation 1st quarter prior to the start of the survey study, ( C ) Elevation, ( D ) NDVI, ( E ) Isothermality, ( F ) Precipitation of the wettest quarter, and ( G ) Precipitation of the driest quarter for P. vivax in Asia.

Marginal predictions based on socio-demographic and epidemiological predictors ( A ) Year at which the survey study started, ( B ) Gross domestic product per capita, ( C ) Population density, ( D ) Human development index, and ( E ) Basic reproductive number ( R 0) 1st quarter prior to the start of the survey study for P. vivax in Asia.

In Fig.  6 , the relationship between socio-demographic and epidemiological factors with P. vivax malaria in Asia are shown. Trends and values at which P. vivax malaria meet maximal values are very similar between the two modeling approaches. For example, high P. vivax malaria occurs before 2000, then both GLM and CART models showed a constant decline after 2001 (Fig.  6 A). Gross domestic product per capita (GDPPC) showed a unimodal response where P. vivax malaria peaks around $3,294.5/year (Fig.  6 B). Population density showed a positive relationship with P. vivax malaria which increases as population density increases (Fig.  6 C). Interestingly, the marginal relationship between the relative temperature dependent basic reproductive number ( R 0 ) and P. vivax malaria shows a relationship that is flat or ambiguous at low values, but then increases as R 0 increases towards one (Fig.  6 E). The pruned tree for P. vivax malaria in Asia from the CART model is given in Supplemental Material (See section A.4), along with the coefficients, standard errors, and P-values from the GLM model (Table S3), a graph with the magnitude and uncertainty of the effects of each variable of the GLM model (Figure S11), and the graphs for the randomized quantile residuals and the density plot from the GLM Model (Figures S12-E and S12-F). Furthermore, in Figure S8 we are showing the correlation between variables included in this study.

Assessing the long-term effects of environmental, geographic, socio-demographic, and epidemiological factors on malaria is essential for public health planning, risk mitigation, and vector control, especially in the context of malaria resurgence 4 , 69 , 70 , 71 . This study examined spatially and temporally resolved predictors on Plasmodium falciparum and Plasmodium vivax malaria presence for a period of 27 years (1990–2017) at the community level for two continents, Africa and Asia. We applied two common methods to analyze binary (presence/absence) data, GLMs and CART 72 , 73 , 74 , 75 , and examined the similarities and dissimilarities in the prediction of malaria. Predicted malaria and its marginal association with the suite of factors showed similar responses with both approaches, but the CART model had better out of sample performance in terms of accuracy, precision, and F1-scores. Other studies have found similar results when comparing GLM and CART models 76 . Three key features of the models and data may have impacted our discussion and interpretation of results. First, because the data are aggregated from multiple studies, often focused on finding malaria, rather than designed to estimate underlying prevalence within either continent, we would expect that overall incidence is likely biased upward in this sample. Second, adjustments to spatial and temporal resolution could have introduced some distortion to the results, however we assumed these distortions are very small since the model results are very similar to other studies or are in the range of expected values. Third, all results are conditional on the inclusion of other aspects of the model, and many factors covary. Thus, we focus primarily on qualitative patterns (shapes, relative factors, etc.) rather than quantitative predictions such as specific prevalence estimates in a region.

The role of temperature

A variety of previous work in the thermal biology of vector-borne diseases has posited that we expect to see unimodal relationships between temperature and transmission 14 , 77 . In our study here, across both types of fitting approaches, and a variety of temperature metrics, we found that this general pattern held, even with the presence of covarying factors, such as temperature and elevation. For example, the relationship between average temperature of the prior quarter and P. falciparum malaria presence in Africa was observed to be unimodal, with a predicted optimum temperature for malaria presence of 24.9  ° C (GLM model) and 24.8  ° C (CART model), with lower and upper thermal limits of 12  ° C and 36  ° C respectively. Similarly, the optimum temperature two quarters before the time the survey study took place was also hump shaped and the estimated optimum temperatures were 25.4  ° C (GLM model) and 25.1  ° C (CART model) for P. falciparum malaria in Africa. These temperatures are very similar to published optimum temperatures for the transmission of P. falciparum by Anopheles gambiae (25  ° C) and by An. stephensi (24.8 ° C) 11 , 15 . The native An. gambiae mosquito is the main malaria vector in Africa 78 and An. stephensi is a recent invasive species in Africa 25 with a greater thermal range than the native vector 15 , so we may find that these predictions would shift in the future as An. stephensi becomes more established.

In the models for data from Asia, similar unimodal patterns between temperature variables and malaria presence were observed. The relationship between average temperature of the 1st quarter prior to the studies showed a unimodal response for P. vivax malaria, with a predicted optimum temperature of 24.7  ° C (CART model) and 24  ° C (GLM model). These temperatures are slightly lower than the optimum transmission temperature suggested in Villena et al. 15 which is 25  ° C, and lower than the optimum in Africa for the same period. This could be possible because in Asia, malaria is transmitted by multiple vectors (e.g., An. dirus , An. culicifacies , An. maculatus ) whose thermal performance curves could be different than An. stephensi 79 , while in Africa An. gambiae is the main vector 4 . The optimum temperature two quarters prior to the survey study for P. falciparum and P. vivax malaria in Asia was in average 4 ° C lower than these other studies. These last results highlight the potential differences between mechanistically driven models, and correlational models (such as the ones we explore here). Although the correlational study can also capture other factors that might be related to the presence of malaria besides temperature, a signal may not be as clear especially in the presence of correlated predictors. Similarly, the mechanistic approaches could over-simplify by examining only one or a few vector species, for example.

The response of life history traits (e.g., mosquito and parasite development rate) to different constant temperatures under laboratory conditions were used in Villena et al. and Mordecai et al. 11 , 15 to estimate the optimum temperature for malaria transmission. However, climatic factors do not typically have instantaneous effects on transmission; rather they may have delayed effects 80 , 81 , 82 . In contrast, in the field, environmental temperatures that influence parasite and vector development are rarely constant. Here we included isothermality as a factor to try to capture the separate relationship of this variability. In the fitted models here, we found that the marginal relationship of P. falciparum malaria in Africa with isothermality increased when temperature oscillations were up to 58%, but did not increase substantially for higher levels of variation. In Asia, both P. falciparum and P. vivax malaria showed a bell-shaped response with isothermality, highest malaria presence at oscillations around 62%. It is known that daily temperature fluctuations affect vector biology, as well as parasite development and infection rates 83 , 84 . Temperature oscillations also impact the abundance and age structure of Anopheles mosquitoes 85 . The relationships identified in this study between malaria transmission and isothermality reflect the findings of other studies. Paaijmans et al. 83 showed that temperature fluctuations around low mean temperatures speed up biological processes, while fluctuations around high mean temperatures slow down biological processes of the vector and the parasite 84 . Zhao et al. 84 found that large daily temperature oscillations speed up malaria incidence in cooler environmental conditions, but in warmer regions large daily temperature oscillations will slow down malaria incidence.

The role of precipitation

In this study, the four precipitation variables (i,e., precipitation one and two quarters prior to the survey study start and precipitation of the wettest and driest quarters) showed a curve-like response with a positive relationship with P. falciparum malaria in Africa up to a certain level of cumulative precipitation and then a decline. For example, precipitation of the wettest quarter (BIO16) positively impacts P. falciparum malaria, to a peak of 1350 mm and 930 mm of quarterly cumulative rainfall for the GLM and CART models respectively; and greater amounts of rainfall have a negative effect on malaria. Similar patterns were observed with precipitation one and two quarters prior to the survey study, and for precipitation of the driest quarter (BIO17). It is well established that precipitation plays a major role in the availability of habitat for immature stages (i.e., eggs, larvae, pupae) of Anopheles mosquitoes, however excess precipitation can flush away immature life stages from these habitats 86 . Most of the African continent is classified as semi-arid, with an average annual precipitation of 469.9 mm in a single summer wet season (December—March), except countries located near the equator where two wet seasons occur, with increased rainfall 87 . Countries located between 10 N and 10 S latitudes have optimal amounts of precipitation (< 1350 mm) for Anopheles mosquito development, with the exception of small areas that experience more than 1350 mm rainfall for at least three months of the year, such as in Gambia, Guinea-Bissau, Guinea, Sierra Leone, Liberia, Nigeria, Cameroon, Equatorial Guinea, Gabon, and Madagascar 87 . Yet, outside these periods of heavy rains, these areas are also optimal for mosquito development in terms of precipitation 87 . Changes in rainfall patterns due to global climate change can have profound consequences on mosquito development and transmission of vector-borne diseases 7 , 88 , 89  . Rainfall trends have already been changing, such as decreases in East Africa and increases in Southern Africa 89 , 90 .

In Asia, the models revealed counterintuitive relationships between P. falciparum malaria presence and precipitation. Increases in mean precipitation one and two quarters prior to the survey study corresponded with a constant decline in malaria. Precipitation of the driest quarter (BIO 17) also had a strong negative correlation with malaria presence, where despite a peak at 210 mm of rainfall (GLM and CART models), malaria activity sharply decreases with increased precipitation. Similar relationships were found for Plasmodium vivax malaria presence, wherein the precipitation of the driest quarter (BIO17), and the mean precipitation of the second quarter prior the survey study show strong negative relationships. As with P. falciparum , precipitation of the driest quarter showed peak P. vivax presence when precipitation is around 210 mm (GLM and CART models), after which malaria decreases with increased precipitation. Plasmodium vivax presence also increases with precipitation of the wettest quarter (BIO16) until an optimum (900 mm) is reached, after which malaria presence decreases with continued rainfall. These findings align with those presented in 91 , which showed that 60 to 80 mm of monthly rainfall is enough to increase availability of breeding sites for mosquitoes and indirectly drive malaria transmission. This echoes findings in Africa, where locally intense rain events that exceed optima can decrease early-stage larvae and pupae through the flushing of ovipositional habitats 92 .

The role of normalized difference vegetation index – NDVI

NDVI relates to malaria in Asia with a bell-shaped response, where malaria presence of both P. falciparum and P. vivax was rise up to an optimum value ( P. falciparum : 0.52 (GLM) and 0.54 (CART); P. vivax : 0.4 (GLM) and 0.5 (CART)), beyond which malaria was predicted to decrease. Multiple studies have shown higher numbers of malaria cases in areas with low to medium density of vegetation. For example, the number of malaria cases increases when forested areas are deforested, which results in NDVI values similar to those that favor malaria presence in this study 93 . The study of Nihei et al. 94 also found a positive correlation with P. falciparum malaria when NDVI values are of 0.4 + for at least 6 months. The GLM model for P. vivax showed a constant increase of malaria as NDVI increases up to 0.8 index; however, between 0.4 and 0.8 the rate of increase is minimal.

The NDVI also showed a bell-shaped response with P. falciparum malaria which was positively impacted up to an optimum value of NDVI = 0.73, beyond which malaria decreased. However, this variable is not determinant for P. falciparum malaria presence in Africa. This could be because of the difference in vegetation cover and its variation from country to country in Africa. For example, In Uganda, malaria incidence was greater when the average NDVI = 0.72 95 while in Kenya the overall effect of NDVI was highest when NDVI was below 0.4 96 .

The role of socio-economic and demographic factors

Gross domestic product per capita (GDPPC) is associated with increased P. falciparum in Africa, and both P. falciparum and P. vivax in Asia. Malaria increases with GDPPC to a certain point, after which it decreases. Notably, in Asia most countries have a GDPPC greater than the thresholds identified in this study ($2,322 for P. falciparum ; $3,294.5 for P. vivax ). In contrast, many countries in Africa have a GDPPC well below the regional threshold ($2,250) for high malaria prevalence 97 . Multiple studies have shown a strong correlation between high malaria burden and low GDPPC 98 , or low per capita income 97 , 99 . For example, the Sarma et al. study 99 found a 10% decrease in malaria incidence with an increase of 0.3% in average income per capita. This is important, as malaria endemic countries also show some of the lowest rates of economic growth globally 100 . This could be worse in coming years if we consider that current and projected annual gross domestic product growth is smaller, particularly for regions in Africa 100 , 101 .

Population density had a weakly positive relationship with P. falciparum malaria in Africa. Increase in population density was associated with increasing malaria until a density of about 898 people per square kilometer; then malaria decreased as population density increased. Multiple studies have found similar results where malaria transmission increases as population density increases, up to a peak of around 1000 pp/km 2 , and then malaria transmission decreases in populated areas with densities greater than 1000 pp/km 2 20 . Malaria has been considered as less of a problem in urban areas compared to rural areas in Africa 102 . However, the relationship between population density and malaria burden may drastically change in the future if the invasive mosquito An. stephensi became established in Africa, due to its proclivity for reproducing in urban and highly populated areas 25 , 103 . In southeast Asia, malaria is also more of a problem in rural areas than in very dense cities 104 . Economic development and environmental changes (e.g. drainage of mosquito breeding sites, improved housing) during the twentieth century have reduced the incidence of malaria in urban contexts 105 .

Other factors driving malaria

The year that malaria survey studies took place and the human development index showed a strong and weak negative relationship with P. falciparum malaria respectively. Both the GLM and the CART model showed a sharp decline in malaria from 2000 to 2010. However, after 2010, the GLM model showed a slowdown in the decline of P. falciparum malaria while the CART model showed a constant increase of P. falciparum malaria. We need to take into account that our P. falciparum malaria survey data comes mostly from the east part of Africa (Ethiopia, Somalia, Kenya, Tanzania, Mozambique, Zimbabwe, and Madagascar) where presence of malaria is higher and less from the west coast of Africa (The Gambia, Guinea-Bissau, Nigeria, Cameroon, and Sao Tome and Principe). Our models capture well the start of the malaria decline which started around 2000 when there was increased funding for malaria control 106 . Also, our models capture the resurgence of malaria in the last 8 to 10 years. The last malaria report from the World Health Organization (WHO) showed that the number of malaria cases and deaths had been increasing globally since 2016 4 and in Africa since 2014 4 , 107 . Multiple studies found that the resurgence of malaria in Africa is related to multiple factors such as the rebound or delayed malaria 108 , insecticide resistance or ineffective new insecticides 109 , 110 , the effects of climate change 15 , and the presence of a new vector, the invasive An. stephensi 103 . Both of our models showed that P. falciparum malaria is higher in countries with low human development index (HDI), a summary of health, education, and income indicators, and malaria decreases as the HDI increases. Multiple studies had found similar results where malaria incidence rates are higher in countries with lower values of HDI 111 .

Similarly to the results for the African continent, both the GLM and CART models captured the start of P. falciparum malaria decline in the 2000s in Asia well. Both of the models captured a slowing down in the decline of malaria around 2010 and a resurgence following this, especially the GLM model. The last malaria report from the World Health Organization (WHO) showed that the number of malaria cases and deaths had been increasing globally since 2016 4 . Similarly to Africa, the causes of malaria resurgence are multiple such as insecticide resistance or ineffective new insecticides 109 , 110 and the effects of climate change 15 . Both models showed a gentle decrease of P. vivax malaria from 1990 to 2003, followed by a rapid decrease of P. vivax malaria after 2003. Finally, P. falciparum malaria in Africa was positively correlated with the basic reproductive number ( R 0 ). The basic reproductive number is an important and widely used indicator of the dynamics of malaria 112 , 113 .

Conclusions

This study presents important progress in understanding the long-term influence of environmental, geographic, socio-demographic, and epidemiological factors on malaria in Africa and Asia. This provides key information on the relative roles of climate driver timing, key demographic features of affected populations, and geographies, that can inform planning strategies and interventions to reduce malaria burden in these two continents. While a ’one model fits all’ approach may not be globally appropriate for predictive frameworks, a CART framing allows us to see how continental differences in responses to this suite of variables arise, and captures the changing dynamics of malaria throughout the time-frame of the data.

Data availability

Malaria survey data was collected by the Malaria Atlas Project following the General Data Protection Regulation (GDPR) and associated data protection legislation, https://malariaatlas.org/privacy-policy/ . Malaria survey data used in this study is publicly available online ( https://malariaatlas.org/ ) as well as all environmental, geographic, and socio-demographic raster layers used in this study as described within the paper. R Code for creating model outputs is available publicly on Zenodo at https://doi.org/10.5281/zenodo.11194470 .

Abbreviations

Generalized linear models

Classification and regression trees

Gross domestic product per capita

Human development index

Mosquito-borne diseases

Normalized difference vegetation index

Basic reproductive number

United States geological survey

Famine early warning systems network

Moderate resolution imaging spectroradiometer

National aeronautics and space administration

Network common data form

Global Rural–Urban Mapping Project

Malaria Atlas Project

Randomized quantile residuals

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Acknowledgements

We thank the technicians, partners, and collaborators of the Malaria Atlas Project that collected and made the malaria prevalence data available to be used for research. This study was supported by the Earth Commons—Georgetown University’s Institute for Environmental and Sustainability. CAL, LRJ, and SJR were supported in part by CIBR: VectorByte: a Global Informatics Platform for studying the Ecology of Vector-Borne Diseases [Division of Biological Infrastructure, National Science Foundation (NSF) 2016265]. LRJ was also supported by the NSF DMS/DEB #1750113.

OCV and AA were supported by the Earth Commons Institute—Georgetown University. LRJ, SJR, and CAL were supported in part by CIBR: VectorByte: a Global Informatics Platform for studying the Ecology of Vector-Borne Diseases [Division of Biological Infrastructure, National Science Foundation (NSF) 2016265]. LRJ and OCV were also supported by the NSF DMS/DEB #1750113.

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Oswaldo C. Villena

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Catherine A. Lippi & Sadie J. Ryan

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Department of Statistics, Virginia Tech, Blacksburg, VA, 24061, USA

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Conceptualization, O.C.V. and L.R.J.; methodology, O.C.V., L.R.J., A.A., S.J.R., and C.A.L.; formal analysis, O.C.V., L.R.J., and A.A.; data curation, O.C.V., C.A.L. writing-original draft, O.C.V. and L.R.J.; writing-review and editing, O.C.V., L.R.J., A.A., S.J.R., and C.A.L. All authors have read and agreed to the published version of the manuscript.

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Villena, O.C., Arab, A., Lippi, C.A. et al. Influence of environmental, geographic, socio-demographic, and epidemiological factors on presence of malaria at the community level in two continents. Sci Rep 14 , 16734 (2024). https://doi.org/10.1038/s41598-024-67452-5

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DOI : https://doi.org/10.1038/s41598-024-67452-5

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The Unintended Consequences of Success Against Malaria

For Immediate Release

For decades, insecticide-treated bed nets and indoor insecticide spraying regimens have been important – and widely successful – treatments against mosquitoes that transmit malaria, a dangerous global disease. Yet these treatments also – for a time – suppressed undesirable household insects like bed bugs, cockroaches and flies.

Now, a new North Carolina State University study reviewing the academic literature on indoor pest control shows that as the household insects developed resistance to the insecticides targeting mosquitoes, the return of these bed bugs, cockroaches and flies into homes has led to community distrust and often abandonment of these treatments – and to rising rates of malaria.

In short, the bed nets and insecticide treatments that were so effective in preventing mosquito bites – and therefore malaria – are increasingly viewed as the causes of household pest resurgence.

“These insecticide-treated bed nets were not intended to kill household pests like bed bugs, but they were really good at it,” said Chris Hayes, an NC State Ph.D. student and co-corresponding author of a paper describing the work. “It’s what people really liked, but the insecticides are not working as effectively on household pests anymore.”

“Non-target effects are usually harmful, but in this case they were beneficial,” said Coby Schal, Blanton J. Whitmire Distinguished Professor of Entomology at NC State and co-corresponding author of the paper.

“The value to people wasn’t necessarily in reducing malaria, but was in killing other pests,” Hayes added. “There’s probably a link between use of these nets and widespread insecticide resistance in these house pests, at least in Africa.”

The researchers add that other factors – famine, war, the rural/city divide, and population displacement, for example – also could contribute to rising rates of malaria.

To produce the review, Hayes combed through the academic literature to find research on indoor pests like bed bugs, cockroaches and fleas, as well as papers on malaria, bed nets, pesticides and indoor pest control. The search yielded more than 1,200 papers, which, after an exhaustive review process, was whittled down to a final count of 28 peer-reviewed papers fulfilling the necessary criteria.

One paper – a 2022 survey of 1,000 households in Botswana – found that while 58% were most concerned with mosquitoes in homes, more than 40% were most concerned with cockroaches and flies.

Hayes said a recent paper – published after this NC State review was concluded – showed that people blamed the presence of bed bugs on bed nets.

“There is some evidence that people stop using bed nets when they don’t control pests,” Hayes said.

The researchers say that all hope is not lost, though.

“There are, ideally, two routes,” Schal said. “One would be a two-pronged approach with both mosquito treatment and a separate urban pest management treatment that targets pests. The other would be the discovery of new malaria-control tools that also target these household pests at the same time. For example, the bottom portion of a bed net could be a different chemistry that targets cockroaches and bed bugs.

“If you offer something in bed nets that suppresses pests, you might reduce the vilification of bed nets.”

The study appears in Proceedings of the Royal Society B . The review was supported in part by the Blanton J. Whitmire Endowment at NC State, and grants from the U.S. Department of Housing and Urban Development Healthy Homes program (NCHHU0053-19), the Department of the Army, U.S. Army Contracting Command, Aberdeen Proving Ground, Natick Contracting Division, Ft. Detrick, Maryland (W911QY1910011), and the Triangle Center for Evolutionary Medicine (257367).

-kulikowski-

Note to editors : The abstract of the paper follows.

“Review on the impacts of indoor vector control on domiciliary pests: good intentions challenged by harsh realities”

Authors: Chris Hayes and Coby Schal, NC State University

Published: July 24, 2024 in Proceedings of the Royal Society B

DOI: 10.1098/rspb.2024.0609

Abstract : Arthropod vectored diseases have been a major impediment to societal advancements globally. Strategies to mitigate transmission of these diseases include preventative care (e.g., vaccination), primary treatment, and most notably the suppression of vectors in both indoor and outdoor spaces. The outcomes of indoor vector control (IVC) strategies, such as long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS), are heavily influenced by individual and community-level perceptions and acceptance. These perceptions, and therefore product acceptance, are largely influenced by the successful suppression of non-target nuisance pests such as bed bugs and cockroaches. Adoption and consistent use of LLINs and IRS is responsible for immense reductions in the prevalence and incidence of Malaria. However, recent observations suggest that failed control of indoor pests, leading to product distrust and abandonment, may threaten vector control program success and further derail already slowed progress towards malaria elimination. We review the evidence of the relationship between IVC and nuisance pests and discuss the dearth of research on this relationship. We make the case that the ancillary control of indoor nuisance and public health pests needs to be considered in the development and implementation of new technologies for malaria elimination.

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UB faculty member launches debut essay collection with Aug. 6 book talk

By Bert Gambini

Release Date: July 29, 2024

BUFFALO, N.Y. – Laura Marris, a visiting assistant professor in the University at Buffalo Department of English, will launch her debut essay collection, “The Age of Loneliness” (Graywolf Press), at 6 p.m. Aug. 6 at Fitz Books, 433 Ellicott St. in Buffalo, with a reading and conversation.

Marris turns to the environment in her first solo-authored book since translating into English Albert Camus’ “The Plague.” Her work on the French literary classic for the Knopf Doubleday Publishing Group was the first updated translation of Camus’ book for an American audience since 1948.

Marris’ thoughtful meditations in “The Age of Loneliness” call attention to the growing separation between people and more-than-human stories of place. By situating personal experience in the context of natural history, she provides readers with clear sightlines toward the history of local places, and an appreciation for their ecology and scales of time.

“I hope people will use these essays as an occasion to investigate and sit with the human and more-than-human histories that are unfolding in the places of their own lives, especially the histories that might previously have been invisible,” says Marris.

The idea for the book emerged in 2018, Marris’ first year in Buffalo, when she was commuting to her job at Boston University for part of each week, as she and her husband worked to get two jobs in the same place. She started reading about ecological issues to put the loneliness of her commute into perspective.

“At first, I didn’t think personal loneliness and landscapes were related, but I began to see connections between issues of ecology and my lonely commutes,” says Marris. “My long-distance relationship was also an estranged relationship to the natural world.”

In many ways, the closer we are to a place the harder it is to see what is missing. Familiarity softens perceptions, and a decline in what was once common can escape notice as it becomes increasingly scarce, according to Marris.

“If you’re not paying attention, if you’re not thinking about absence, then it’s difficult to recognize the changes in landscapes that are occurring every day,” she says.

Landscape, for Marris, is an appropriate representation for the way humans have interacted with their environment, because it can imply not only what’s seen, but what has been modified.

“Everything around us is touched by humans,” she says. “There isn’t a pristine place that lacks human imprint.”

Although the Anthropocene is customarily used to identify the current geological era — defined by human impacts in earth’s fossil record — Marris instead uses her essays to explore the implications of the Eremocene. Coined by biologist E.O. Wilson, the Eremocene, or the age of loneliness, is a time of declining abundance and humanity’s subsequent isolation, if humans allow wildlife loss to continue unabated.

“It’s interesting to investigate things through the lens of loneliness because the root word of Eremocene can mean a lonely person or a desolated place,” says Marris. “If we make a place lonely then we become lonely ourselves, because that reciprocity is a reflection of the broader ecosystem.”

But places are resilient, and the underlying sense of hope in Marris’ book comes with recognizing that measurable action doesn’t need to be a grand effort. Community projects can make a big difference.

“Community science, for example, which is an important part of the book, is a way of discovering what’s happing in a place, from bird counts, to planting a garden, to helping with a survey,” says Marris. “The gains are impressive when people push their grief slightly toward longing for, and cultivating, the abundant landscapes they’d like to see.”

And through the process of writing the book, Marris feels that change in herself.

“I began in a more alienated place as a commuter, writing and returning to the woods,” she says. “I didn’t expect the book to moderate my own fears, but through the ground-truth of community science, I became more grounded in my personal and ecological relationship to these places.”

Awareness can inspire change. And it’s time to start looking, since, as Marris points out through a quote in the book from Walt Whitman, “much unseen is also here.”

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NeurIPS 2024 Datasets and Benchmarks Track

If you'd like to become a reviewer for the track, or recommend someone, please use this form .

The Datasets and Benchmarks track serves as a venue for high-quality publications, talks, and posters on highly valuable machine learning datasets and benchmarks, as well as a forum for discussions on how to improve dataset development. Datasets and benchmarks are crucial for the development of machine learning methods, but also require their own publishing and reviewing guidelines. For instance, datasets can often not be reviewed in a double-blind fashion, and hence full anonymization will not be required. On the other hand, they do require additional specific checks, such as a proper description of how the data was collected, whether they show intrinsic bias, and whether they will remain accessible. The Datasets and Benchmarks track is proud to support the open source movement by encouraging submissions of open-source libraries and tools that enable or accelerate ML research.

The previous editions of the Datasets and Benchmarks track were highly successful; you can view the accepted papers from 2021 , 2002 , and 2023 , and the winners of the best paper awards 2021 , 2022 and 2023

CRITERIA. W e are aiming for an equally stringent review as the main conference, yet better suited to datasets and benchmarks. Submissions to this track will be reviewed according to a set of criteria and best practices specifically designed for datasets and benchmarks , as described below. A key criterion is accessibility: datasets should be available and accessible , i.e. the data can be found and obtained without a personal request to the PI, and any required code should be open source. We encourage the authors to use Croissant format ( https://mlcommons.org/working-groups/data/croissant/ ) to document their datasets in machine readable way.   Next to a scientific paper, authors should also submit supplementary materials such as detail on how the data was collected and organised, what kind of information it contains, how it should be used ethically and responsibly, as well as how it will be made available and maintained.

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SUBMISSIONS.  There will be one deadline this year. It is also still possible to submit datasets and benchmarks to the main conference (under the usual review process), but dual submission to both is not allowed (unless you retracted your paper from the main conference). We also cannot transfer papers from the main track to the D&B track. Authors can choose to submit either single-blind or double-blind . If it is possible to properly review the submission double-blind, i.e., reviewers do not need access to non-anonymous repositories to review the work, then authors can also choose to submit the work anonymously. Papers will not be publicly visible during the review process. Only accepted papers will become visible afterward. The reviews themselves are not visible during the review phase but will be published after decisions have been made. The datasets themselves should be accessible to reviewers but can be publicly released at a later date (see below). New authors cannot be added after the abstract deadline and they should have an OpenReview profile by the paper deadline. NeurIPS does not tolerate any collusion whereby authors secretly cooperate with reviewers, ACs or SACs to obtain favourable reviews.

SCOPE. This track welcomes all work on data-centric machine learning research (DMLR) and open-source libraries and tools that enable or accelerate ML research, covering ML datasets and benchmarks as well as algorithms, tools, methods, and analyses for working with ML data. This includes but is not limited to:

• New datasets, or carefully and thoughtfully designed (collections of) datasets based on previously available data.
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Read our original blog post for more about why we started this track.

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• Review deadline - Jul 24, 2024
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Q: My work is in scope for this track but possibly also for the main conference. Where should I submit it?

A: This is ultimately your choice. Consider the main contribution of the submission and how it should be reviewed. If the main contribution is a new dataset, benchmark, or other work that falls into the scope of the track (see above), then it is ideally reviewed accordingly. As discussed in our blog post, the reviewing procedures of the main conference are focused on algorithmic advances, analysis, and applications, while the reviewing in this track is equally stringent but designed to properly assess datasets and benchmarks. Other, more practical considerations are that this track allows single-blind reviewing (since anonymization is often impossible for hosted datasets) and intended audience, i.e., make your work more visible for people looking for datasets and benchmarks.

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A: This will be possible on the condition that a credentialization is necessary for the public good (e.g. because of ethically sensitive medical data), and that an established credentialization procedure is in place that is 1) open to a large section of the public, 2) provides rapid response and access to the data, and 3) is guaranteed to be maintained for many years. A good example here is PhysioNet Credentialing, where users must first understand how to handle data with human subjects, yet is open to anyone who has learned and agrees with the rules. This should be seen as an exceptional measure, and NOT as a way to limit access to data for other reasons (e.g. to shield data behind a Data Transfer Agreement). Misuse would be grounds for desk rejection. During submission, you can indicate that your dataset involves open credentialized access, in which case the necessity, openness, and efficiency of the credentialization process itself will also be checked.

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A submission consists of:

• Please carefully follow the Latex template for this track when preparing proposals. We follow the NeurIPS format, but with the appropriate headings, and without hiding the names of the authors. Download the template as a bundle here .
• Papers should be submitted via OpenReview
• Reviewing is in principle single-blind, hence the paper should not be anonymized. In cases where the work can be reviewed equally well anonymously, anonymous submission is also allowed.
• During submission, you can add a public link to the dataset or benchmark data. If the dataset can only be released later, you must include instructions for reviewers on how to access the dataset. This can only be done after the first submission by sending an official note to the reviewers in OpenReview. We highly recommend making the dataset publicly available immediately or before the start of the NeurIPS conference. In select cases, requiring solid motivation, the release date can be stretched up to a year after the submission deadline.
• Dataset documentation and intended uses. Recommended documentation frameworks include datasheets for datasets , dataset nutrition labels , data statements for NLP , data cards , and accountability frameworks .
• URL to website/platform where the dataset/benchmark can be viewed and downloaded by the reviewers. 
• URL to Croissant metadata record documenting the dataset/benchmark available for viewing and downloading by the reviewers. You can create your Croissant metadata using e.g. the Python library available here: https://github.com/mlcommons/croissant
• Author statement that they bear all responsibility in case of violation of rights, etc., and confirmation of the data license.
• Hosting, licensing, and maintenance plan. The choice of hosting platform is yours, as long as you ensure access to the data (possibly through a curated interface) and will provide the necessary maintenance.
• Links to access the dataset and its metadata. This can be hidden upon submission if the dataset is not yet publicly available but must be added in the camera-ready version. In select cases, e.g when the data can only be released at a later date, this can be added afterward (up to a year after the submission deadline). Simulation environments should link to open source code repositories
• The dataset itself should ideally use an open and widely used data format. Provide a detailed explanation on how the dataset can be read. For simulation environments, use existing frameworks or explain how they can be used.
• Long-term preservation: It must be clear that the dataset will be available for a long time, either by uploading to a data repository or by explaining how the authors themselves will ensure this
• Explicit license: Authors must choose a license, ideally a CC license for datasets, or an open source license for code (e.g. RL environments). An overview of licenses can be found here: https://paperswithcode.com/datasets/license
• Add structured metadata to a dataset's meta-data page using Web standards (like schema.org and DCAT ): This allows it to be discovered and organized by anyone. A guide can be found here: https://developers.google.com/search/docs/data-types/dataset . If you use an existing data repository, this is often done automatically.
• Highly recommended: a persistent dereferenceable identifier (e.g. a DOI  minted by a data repository or a prefix on identifiers.org ) for datasets, or a code repository (e.g. GitHub, GitLab,...) for code. If this is not possible or useful, please explain why.
• For benchmarks, the supplementary materials must ensure that all results are easily reproducible. Where possible, use a reproducibility framework such as the ML reproducibility checklist , or otherwise guarantee that all results can be easily reproduced, i.e. all necessary datasets, code, and evaluation procedures must be accessible and documented.
• For papers introducing best practices in creating or curating datasets and benchmarks, the above supplementary materials are not required.
• For papers resubmitted after being retracted from another venue: a brief discussion on the main concerns raised by previous reviewers and how you addressed them. You do not need to share the original reviews.
• For the dual submission and archiving, the policy follows the NeurIPS main track paper guideline .

Use of Large Language Models (LLMs): We welcome authors to use any tool that is suitable for preparing high-quality papers and research. However, we ask authors to keep in mind two important criteria. First, we expect papers to fully describe their methodology, and any tool that is important to that methodology, including the use of LLMs, should be described also. For example, authors should mention tools (including LLMs) that were used for data processing or filtering, visualization, facilitating or running experiments, and proving theorems. It may also be advisable to describe the use of LLMs in implementing the method (if this corresponds to an important, original, or non-standard component of the approach). Second, authors are responsible for the entire content of the paper, including all text and figures, so while authors are welcome to use any tool they wish for writing the paper, they must ensure that all text is correct and original.

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Reviewing will be single-blind, although authors can also submit anonymously if the submission allows that. A datasets and benchmarks program committee will be formed, consisting of experts on machine learning, dataset curation, and ethics. We will ensure diversity in the program committee, both in terms of background as well as technical expertise (e.g., data, ML, data ethics, social science expertise). Each paper will be reviewed by the members of the committee. In select cases where ethical concerns are flagged by reviewers, an ethics review may be performed as well.

Papers will not be publicly visible during the review process. Only accepted papers will become visible afterward. The reviews themselves are also not visible during the review phase but will be published after decisions have been made. Authors can choose to keep the datasets themselves hidden until a later release date, as long as reviewers have access.

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• Utility and quality of the submission: Impact, originality, novelty, relevance to the NeurIPS community will all be considered. 
• Reproducibility: All submissions should be accompanied by sufficient information to reproduce the results described i.e. all necessary datasets, code, and evaluation procedures must be accessible and documented. We encourage the use of a reproducibility framework such as the ML reproducibility checklist to guarantee that all results can be easily reproduced. Benchmark submissions in particular should take care to ensure sufficient details are provided to ensure reproducibility. If submissions include code, please refer to the NeurIPS code submission guidelines .  
• Was code provided (e.g. in the supplementary material)? If provided, did you look at the code? Did you consider it useful in guiding your review? If not provided, did you wish code had been available?
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• Completeness of the relevant documentation: Per NeurIPS ethics guidelines , datasets must be accompanied by documentation communicating the details of the dataset as part of their submissions via structured templates (e.g. TODO). Sufficient detail must be provided on how the data was collected and organized, what kind of information it contains,  ethically and responsibly, and how it will be made available and maintained. 
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• Consent and privacy: Per  NeurIPS ethics guidelines , datasets should minimize the exposure of any personally identifiable information, unless informed consent from those individuals is provided to do so. Any paper that chooses to create a dataset with real data of real people should ask for the explicit consent of participants, or explain why they were unable to do so.
• Ethics and responsible use: Any ethical implications of new datasets should be addressed and guidelines for responsible use should be provided where appropriate. Note that, if your submission includes publicly available datasets (e.g. as part of a larger benchmark), you should also check these datasets for ethical issues. You remain responsible for the ethical implications of including existing datasets or other data sources in your work.
• Legal compliance: For datasets, authors should ensure awareness and compliance with regional legal requirements.

ADVISORY COMMITTEE

The following committee will provide advice on the organization of the track over the coming years: Sergio Escalera, Isabelle Guyon, Neil Lawrence, Dina Machuve, Olga Russakovsky, Joaquin Vanschoren, Serena Yeung.

DATASETS AND BENCHMARKS CHAIRS

Lora Aroyo, Google Francesco Locatello, Institute of Science and Technology Austria Lingjuan Lyu, Sony AI

Contact: [email protected]

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Institute of Medicine (US) Committee for the Study on Malaria Prevention and Control; Oaks SC Jr., Mitchell VS, Pearson GW, et al., editors. Malaria: Obstacles and Opportunities. Washington (DC): National Academies Press (US); 1991.

Malaria: Obstacles and Opportunities.

• Hardcopy Version at National Academies Press

1 Conclusions and Recommendations

• DEFINING THE PROBLEM

The outlook for malaria control is grim. The disease, caused by mosquito-borne parasites, is present in 102 countries and is responsible for over 100 million clinical cases and 1 to 2 million deaths each year. Over the past two decades, efforts to control malaria have met with less and less success. In many regions where malaria transmission had been almost eliminated, the disease has made a comeback, sometimes surpassing earlier recorded levels. The dream of completely eliminating malaria from many parts of the world, pursued with vigor during the 1950s and 1960s, has gradually faded. Few believe today that a global eradication of malaria will be possible in the foreseeable future.

Worldwide, the number of cases of malaria caused by Plasmodium falciparum , the most dangerous species of the parasite, is on the rise. Drug-resistant strains of P. falciparum are spreading rapidly, and there have been recent reports of drug resistance in people infected with P. vivax , a less virulent form of the parasite. Furthermore, mosquitoes are becoming increasingly resistant to insecticides, and in many cases, have adapted so as to avoid insecticide-treated surfaces altogether.

In large part because of the spread of drug and insecticide resistance, there are fewer tools available today to control malaria than there were 20 years ago. In many countries, the few remaining methods are often applied inappropriately. The situation in many African nations is particularly dismal, exacerbated by a crumbling health infrastructure that has made the implementation of any disease control program difficult.

Malaria cases among tourists, business travelers, military personnel, and migrant workers in malarious areas have been increasing steadily in the last several years, posing new concerns that the disease will be introduced to currently nonmalarious areas. Recent epidemics have claimed tens of thousands of lives in Africa, and there is an increasing realization that malaria is a major impediment to socioeconomic development in many countries. Unless practical, cost-effective strategies can be developed and successfully implemented, malaria will continue to exact a heavy toll on human life and health around the world.

Although often considered a single disease, malaria is more accurately viewed as many diseases, each shaped by subtle interactions of biologic, ecologic, social, and economic factors. The species of parasite, the behavior of the mosquito host, the individual's immune status, the climate, human activities, and access to health services all play important roles in determining the intensity of disease transmission, who will become infected, who will get sick, and who will die.

Gem miners along the Thailand-Cambodia border, American tourists on a wildlife safari in East Africa, villagers living on the central highlands in Madagascar, residents of San Diego County, California, a young pregnant woman in Malawi, Swiss citizens living near Geneva International Airport, children in Africa south of the Sahara, and a U.S. State Department secretary in Tanzania seem to have little in common, yet they are all at risk of contracting malaria. Because of the disease's variable presentations, each will be affected differently, as illustrated below.

• For the hundreds of thousands of Thai seasonal agricultural workers who travel deep into the forest along the Thailand-Cambodia border to mine for gems, malaria is the cost of doing business. These young men are exposed to aggressive forest mosquitoes, and within two to three weeks after arriving, almost every miner will get malaria. Many gem miners seek medications to prevent and self-treat mild cases of the disease. But because malaria in this part of the world is resistant to most antimalarial drugs, the few effective drugs are reserved for the treatment of confirmed cases of malaria. To complicate matters, there are no health services in the forest to treat patients, and the health clinics in Thailand are overburdened by the high demand for treating those with severe malaria, most of whom are returning gem miners. A similar scenario involving over 400,000 people exists among gold miners in Rondonia, Brazil.
• Each year, over seven million U.S. citizens visit parts of the world where malaria is present. Many, at the recommendation of their travel agent or physician, take antimalarial medications as a preventive measure, but a significant number do not. Tourists and other travelers who have never been exposed to malaria, and therefore have never developed protective immunity, are at great risk for contracting severe disease. Ironically, it is not the infection itself that poses the biggest danger, but the chance that treatment will be delayed because of misdiagnosis upon the individual's return to the United States. Most U.S. doctors have never seen a patient with malaria, are often confused by the wide array of symptoms, and are largely unaware that malaria in a nonimmune person can be a medical emergency, sometimes rapidly fatal.
• Prior to 1950, malaria was the major cause of death in the central highlands of the African island nation of Madagascar. In the late 1950s, an aggressive program of indoor insecticide spraying rid the area of malaria-carrying mosquitoes, and malaria virtually disappeared. By the 1970s, confident of a victory in the battle against malaria, Madagascar began to phase out its spraying program; in some areas spraying was halted altogether. In the early 1980s, the vector mosquitoes reinvaded the central highlands, and in 1986 a series of devastating epidemics began. The older members of the population had long since lost the partial immunity they once had, and the younger island residents had no immunity at all. During the worst of the epidemics, tens of thousands of people died in one three-month period. The tragedy of this story is that it could have been prevented. A cheap antimalarial drug, chloroquine, could have been a powerful weapon in Madagascar, where drug resistance was not a significant concern. Because of problems in international and domestic drug supply and delivery, however, many people did not receive treatment and many died. In the last 18 months, surveillance has improved, spraying against the mosquito has resumed, and more effective drug distribution networks have been established. Malaria-related mortality has declined sharply as a result.
• Malaria, once endemic in the southern United States, occurs relatively infrequently. Indeed, there have been only 23 outbreaks of malaria since 1950, and the majority of these occurred in California. But for each of the past three years, the San Diego County Department of Health Services has had to conduct an epidemiologic investigation into local transmission of malaria. An outbreak in the late summer of 1988 involved 30 persons, the largest such outbreak in the United States since 1952. In the summer of 1989, three residents of San Diego County—a migrant worker and two permanent residents—were diagnosed with malaria; in 1990, a teenager living in a suburb of San Diego County fell ill with malaria. All of the cases were treated successfully, but these incidents raise questions about the possibility of new and larger outbreaks in the future. Malaria transmission in San Diego County (and in much of California) is attributed to the presence of individuals from malaria-endemic regions who lack access to medical care, the poor shelter and sanitation facilities of migrant workers, and the ubiquitous presence of Anopheles mosquitoes in California.
• A 24-year-old pregnant Yao woman from the Mangochi District in Malawi visited the village health clinic monthly to receive prenatal care. While waiting to be seen by the health provider, she and other women present listened to health education talks which were often about the dangers of malaria during pregnancy, and the need to install screens around the house to keep the mosquitoes away, to sleep under a bednet, and to take a chloroquine tablet once a week. Toward the end of her second trimester of pregnancy, the woman returned home from her prenatal visit with her eight tablets of chloroquine wrapped in a small packet of brown paper. She promptly gave the medicine to her husband to save for the next time he or one of their children fell ill. The next week she developed a very high malarial fever and went into labor prematurely. The six-month-old fetus was born dead.
• Over a two-week period in the summer of 1989, five Swiss citizens living within a mile of Geneva International Airport presented at several hospitals with acute fever and chills. All had malaria. Four of the five had no history of travel to a malarious region; none had a history of intravenous drug use or blood transfusion. Apart from their symptoms, the only thing linking the five was their proximity to the airport. A subsequent epidemiologic investigation suggested that the malaria miniepidemic was caused by the bite of stowaway mosquitoes en route from a malaria- endemic country. The warm weather, lack of systematic spraying of aircraft, and the close proximity of residential areas to the airport facilitated the transmission of the disease.
• Malaria is a part of everyday life in Africa south of the Sahara. Its impact on children is particularly severe. Mothers who bring unconscious children to the hospital often report that the children were playing that morning, convulsed suddenly, and have been unconscious ever since. These children are suffering from the most frequently fatal complication of the disease, cerebral malaria. Other children succumb more slowly to malaria, becoming progressively more anemic with each subsequent infection. By the time they reach the hospital, they are too weak to sit and are literally gasping for breath. Many children are brought to hospitals as a last resort, after treatment given for “fever” at the local health center has proved ineffective. Overall, children with malaria account for a third of all hospital admissions. A third of all children hospitalized for malaria die. In most parts of Africa, there are no effective or affordable options to prevent the disease, so children are at high risk until they have been infected enough times to develop a partial immunity.
• A 52-year-old American woman, the secretary to the U.S. ambassador in Tanzania, had been taking a weekly dose of chloroquine to prevent malaria since her arrival in the country the year before. She arrived at work one morning complaining of exhaustion, a throbbing headache, and fever. A blood sample was taken and microscopically examined for malaria parasites. She was found to be infected with P. falciparum , and was treated immediately with high doses of chloroquine. That night, she developed severe diarrhea, and by morning she was found to be disoriented and irrational. She was diagnosed as having cerebral malaria, and intravenous quinine treatment was started. Her condition gradually deteriorated—she became semicomatose and anemic, and approximately 20 percent of her red blood cells were found to be infected with malaria parasites. After continued treatment for several days, no parasites were detected in her blood. Despite receiving optimal care, other malaria-related complications developed and she died just nine days after the illness began. The cause of death: chloroquine-resistant P. falciparum .

These brief scenarios give a sense of the diverse ways that malaria can affect people. So fundamental is this diversity with respect to impact, manifestation, and epidemiology that malaria experts themselves are not unanimous on how best to approach the disease. Malariologists recognize that malaria is essentially a local phenomenon that varies greatly from region to region and even from village to village in the same district. Consequently, a single global technology for malaria control is of little use for specific conditions, yet the task of tailoring strategies to each situation is daunting. More important, many malarious countries do not have the resources, either human or financial, to carry out even the most meager efforts to control malaria.

These scenarios also illustrate the dual nature of malaria as it affects U.S. policy. In one sense, it is a foreign aid issue; a devastating disease is currently raging out of control in vast, heavily populated areas of the world. In another sense, malaria is of domestic public health concern. The decay of global malaria control and the invasion of the parasite into previously disease-free areas, coupled with the increasing frequency of visits to such areas by American citizens, intensify the dangers of malaria for the U.S. population. Tourists, business travelers, Peace Corps volunteers, State Department employees, and military personnel are increasingly at risk, and our ability to protect and cure them is in jeopardy. What is desperately needed is a better application of existing malaria control tools and new methods of containing the disease.

In most malarious regions of the world, there is inadequate access to malaria treatment. Appropriate health facilities may not exist; those that do exist may be inaccessible to affected populations, may not be supplied with effective drugs, or may be staffed inappropriately. In many countries, the expansion of primary health care services has not proceeded according to expectations, particularly in the poorest (and most malarious) nations of the tropical world.

In some countries, antimalarial interventions are applied in broad swaths, without regard to underlying differences in the epidemiology of the disease. In other countries, there are no organized interventions at all. The malaria problem in many regions is compounded by migration, civil unrest, poorly planned exploitation of natural resources, and their frequent correlate, poverty.

During the past 15 years, much research has focused on developing vaccines for malaria. Malaria vaccines are thought to be possible in part because people who are naturally exposed to the malaria parasite acquire a partial immunity to the disease over time. In addition, immunization of animals and humans by the bites of irradiated mosquitoes infected with the malaria parasite can protect against malaria infection. Much progress has been made, but current data suggest that effective vaccines are not likely to be available for some time.

Compounding the difficulty of developing more effective malaria prevention, treatment, and control strategies is a worldwide decline in the pool of scientists and health professionals capable of conducting field research and organizing and managing malaria control programs at the country level. With the change in approach from malaria eradication to malaria control, many malaria programs “lost face,” admitting failure and losing the priority interest of their respective ministries of health. As external funding agencies lost interest in programs, they reduced their technical and financial support. As a consequence, there were fewer training opportunities, decreased contacts with international experts, and diminished prospects for improving the situation. Today, many young scientists and public health specialists, in both the developed and developing countries, prefer to seek higher-profile activities with better defined opportunities for career advancement.

It is against this backdrop of a worsening worldwide malaria situation that the Institute of Medicine was asked to convene a multidisciplinary committee to assess the current status of malaria research and control and to make recommendations to the U.S. government on promising and feasible strategies to address the problem. During the 18-month study, the committee reviewed the state of the science in the major areas of malariology, identified gaps in knowledge within each of the major disciplines, and developed recommendations for future action in malaria research and control.

Organization

Chapter 2 summarizes key aspects of the individual state-of-the-science chapters, and is intended to serve as a basic introduction to the medical and scientific aspects of malaria, including its clinical signs, diagnosis, treatment, and control. Chapter 3 provides a historical overview of malaria, from roughly 3000 B.C. to the present, with special emphasis on efforts in this century to eradicate and control the disease. The state-of-the-science reviews, which start in Chapter 4 , begin with a scenario titled “Where We Want To Be in the Year 2010.” Each scenario describes where the discipline would like to be in 20 years and how, given an ideal world, the discipline would have contributed to malaria control efforts. The middle section of each chapter contains a critical review of the current status of knowledge in the particular field. The final section lays out specific directions for future research based on a clear identification of the major gaps in scientific understanding for that discipline. The committee urges those agencies that fund malaria research to consult the end of each state-of-the-science chapter for suggestions on specific research opportunities in malaria.

Sponsorship

This study was sponsored by the U.S. Agency for International Development, the U.S. Army Medical Research and Development Command, and the National Institute of Allergy and Infectious Diseases of the National Institutes of Health.

• CONCLUSIONS AND RECOMMENDATIONS

A major finding of the committee is the need to increase donor and public awareness of the growing risk presented by the resurgence of malaria. Overall, funding levels are not adequate to meet the problem. The committee believes that funding in the past focused too sharply on specific technologies and particular control strategies (e.g., indiscriminate use of insecticide spraying). Future support must be balanced among the needs outlined in this report. The issue for prioritization is not whether to select specific technologies or control strategies, but to raise the priority for solving the problem of malaria. This is best done by encouraging balanced research and control strategies and developing a mechanism for periodically adjusting support for promising approaches.

This report highlights those areas which the committee believes deserve the highest priority for research or which should be considered when U.S. support is provided to malaria control programs. These observations and suggestions for future action, presented below in four sections discussing policy, research, control, and training, represent the views of a multidisciplinary group of professionals from diverse backgrounds and with a variety of perspectives on the problem.

The U.S. government is the largest single source of funds for malaria research and control activities in the world. This investment is justified by the magnitude of the malaria problem, from both a foreign aid and a public health perspective. The increasing severity of the threat of malaria to residents of endemic regions, travelers, and military personnel, and our diminishing ability to counter it, should be addressed by a more comprehensive and better integrated approach to malaria research and control. However, overall U.S. support for malaria research and control has declined over the past five years. The committee believes that the amount of funding currently directed to malaria research and control activities is inadequate to address the problem.

Over the past 10 years, the majority of U.S. funds available for malaria research have been devoted to studies on immunity and vaccine development. Although the promise of vaccines remains to be realized, the committee believes that the potential benefits are enormous. At the same time, the relative paucity of funds available for research has prevented or slowed progress in other areas. Our incomplete knowledge about the basic biology of malaria parasites, how they interact with their mosquito and human hosts, and how human biology and behavior affect malaria transmission and control remains a serious impediment to the development and implementation of malaria control strategies. The committee believes that this situation must be addressed without reducing commitment to current research initiatives. The committee further believes that such research will pay long-term dividends in the better application of existing tools and the development of new drugs, vaccines, and methods for vector control.

The committee recommends that increased funds be made available so that U.S. research on malaria can be broadened according to the priorities addressed in this report, including laboratory and field research on the biology of malaria parasites, their mosquito vectors, and their interaction with humans.

The committee believes that the maximum return on investment of funds devoted to malaria research and control can be achieved only by rigorous review of project proposals. The committee further believes that the highest-quality review is essential to ensure that funding agencies spend their money wisely. The committee believes that all U.S.-supported malaria field activities, both research and control, should be of the highest scientific quality and relevance to the goals of malaria control.

The committee recommends decisions on funding of malaria research be based on scientific merit as determined by rigorous peer review, consistent with the guidelines of the National Institutes of Health or the United Nations Development Program/World Bank/ World Health Organization Special Programme for Research and Training in Tropical Diseases, and that all U.S.-supported malaria field projects be subject to similar rigorous review to ensure that projects are epidemiologically and scientifically sound.

Commitment and Sustainability

For malaria control, short-term interventions can be expected to produce only short-term results. The committee believes that short-term interventions are justified only for emergency situations. Longer-term interventions should be undertaken only when there is a national commitment to support sustained malaria surveillance and control.

The committee recommends that malaria control programs receive sustained international and local support, oriented toward the development of human resources, the improvement of management skills, the provision of supplies, and the integration of an operational research capability in support of an epidemiologically sound approach to malaria control.

Surveillance

During the major effort to eradicate malaria from many parts of the world that began in the late 1950s and ended in 1969, it was important to establish mechanisms to detect all malaria infections. As a result, systems were established in many countries to collect blood samples for later microscopic examination for the presence of parasites. Each year, the results from more than 140 million slides are reported to the World Health Organization, of which roughly 3 to 5 percent are positive for malaria. This approach seeks to answer the question posed 30 years ago: How many people are infected with the malaria parasite? It does not answer today's questions: Who is sick? Where? Why? The committee concludes that the mass collection of blood slides requires considerable resources, poses serious biosafety hazards, deflects attention from the treatment of ill individuals, and has little practical relevance for malaria control efforts today.

Instead of the mass collection of slides, the committee believes that the most effective surveillance networks are those that concurrently measure disease in human populations, antimalarial drug use, patterns of drug resistance, and the intensity of malaria transmission by vector populations. The committee believes that malaria surveillance practices have not received adequate recognition as an epidemiologic tool for designing, implementing, and evaluating malaria control programs.

The committee recommends that countries be given support to orient malaria surveillance away from the mass collection and screening of blood slides toward the collection and analysis of epidemiologically relevant information that can be used to monitor the current situation on an ongoing basis, to identify high-risk groups, and to detect potential epidemics early in their course.

Inter-Sectoral Cooperation

The committee believes that insufficient attention has been paid to the impact that activities in non-health-related sectors, such as construction, industry, irrigation, and agriculture, have on malaria transmission. Conversely, there are few assessments of the impact of malaria control projects on other public health initiatives, the environment, and the socioeconomic status of affected populations. Malaria transmission frequently occurs in areas where private and multinational businesses and corporations (e.g., hotel chains, mining operations, and industrial plants) have strong economic interests. Unfortunately and irresponsibly, some local and multinational businesses contribute few if any resources to malaria control in areas in which they operate.

The committee recommends greater cooperation and consultation between health and nonhealth sectors in the planning and implementation of major development projects and malaria activities. It also recommends that all proposed malaria control programs be analyzed for their potential impact on other public health programs, the environment, and social and economic welfare, and that local and multinational businesses be recruited by malaria control organizations to contribute substantially to local malaria control efforts.

New Tools for Malaria Control

The committee believes that, as a policy directive, it is important to support research activities to develop new tools for malaria control. The greatest momentum for the development of new tools exists in vaccine and drug development, and the committee believes it essential that this momentum be maintained. The committee recognizes that commendable progress has been made in defining the characteristics of antigens and delivery systems needed for effective vaccines, but that the candidates so far tested fall short of the goal. Much has been learned which supports the hope that useful vaccines can be developed. To diminish activity in vaccine development at this stage would deal a severe blow to one of our best chances for a technological breakthrough in malaria control.

The committee recommends that vaccine development continue to be a priority of U.S.-funded malaria research.

Only a handful of drugs are available to prevent or treat malaria, and the spread of drug-resistant strains of the malaria parasite threatens to reduce further the limited pool of effective drugs. The committee recognizes that there is little economic incentive for U.S. pharmaceutical companies to undertake antimalarial drug discovery activities. The committee is concerned that U.S. government support of these activities, based almost entirely at the Walter Reed Army Institute of Research (WRAIR), has decreased and is threatened with further funding cuts. The committee concludes that the WRAIR program in antimalarial drug discovery, which is the largest and most successful in the world, is crucial to international efforts to develop new drugs for malaria. The benefits of this program in terms of worldwide prevention and treatment of malaria have been incalculable.

The committee strongly recommends that drug discovery and development activities at WRAIR receive increased and sustained support.

The next recommendation on policy directions reflects the committee's concern about the lack of involvement in malaria research by the private sector. The committee believes that the production of candidate malaria vaccines and antimalarial drugs for clinical trials has been hampered by a lack of industry involvement. Greater cooperation and a clarification of the contractual relationships between the public and private sectors would greatly enhance the development of drugs and vaccines.

The committee recommends that mechanisms be established to promote the involvement of pharmaceutical and biotechnology firms in the development of malaria vaccines, antimalarial drugs, and new tools for vector control.

Coordination and Integration

The committee is concerned that there is inadequate joint planning and coordination among U.S.-based agencies that support malaria research and control activities. Four government agencies and many nongovernmental organizations in the United States are actively involved in malaria-related activities. There are also numerous overseas organizations, governmental and nongovernmental, that actively support such activities worldwide.

The complexity and variability of malaria, the actual and potential scientific advances in several areas of malariology, and most important the worsening worldwide situation argue strongly for an ongoing mechanism to assess and influence current and future U.S. efforts in malaria research and control.

The committee strongly recommends the establishment of a national advisory body on malaria.

In addition to fulfilling a much needed coordinating function among U.S.-based agencies and between the U.S. and international efforts, the national advisory body could monitor the status of U.S. involvement in malaria research and control, assess the relevant application of knowledge, identify areas requiring further research, make recommendations to the major funding agencies, and provide a resource for legislators and others interested in scientific policy related to malaria. The national advisory body could convene specific task-oriented scientific working groups to review research and control activities and to make recommendations, when appropriate, for changes in priorities and new initiatives.

The committee believes that the national advisory body should be part of, and appointed by, a neutral and nationally respected scientific body and that it should actively encourage the participation of governmental and nongovernmental organizations, industry, and university scientists in advising on the direction of U.S. involvement in malaria research and control.

The increasing magnitude of the malaria problem during the past decade and the unpredictability of changes in human, parasite, and vector determinants of transmission and disease point strongly to the need for such a national advisory body, which can be responsive to rapidly changing problems, and advances in scientific research, relating to global efforts to control malaria.

Malaria Research Priorities

Malaria control is in crisis in many areas of the world. People are contracting and dying of severe malaria in unprecedented numbers. To address these problems, the committee strongly encourages a balanced research agenda. Two basic areas of research require high priority. Research that will lead to improved delivery of existing interventions for malaria, and the development of new tools for the control of malaria.

Research in Support of Available Control Measures

Risk Factors for Severe Malaria People who develop severe and complicated malaria lack adequate immunity, and many die from the disease. Groups at greatest risk include young children and pregnant women in malaria endemic regions; nonimmune migrants, laborers, and visitors to endemic regions; and residents of regions where malaria has been recently reintroduced. For reasons that are largely unknown, not all individuals within these groups appear to be at equal risk for severe disease. The committee believes that the determinants of severe disease, including risk factors associated with a population, the individual (biologic, immunologic, socioeconomic, and behavioral), the parasite, or exposure to mosquitoes, are likely to vary considerably in different areas.

The committee recommends that epidemiologic studies on the risk factors for severe and complicated malaria be supported.

Pathogenesis of Severe and Complicated Malaria Even with optimal care, 20 to 30 percent of children and adults with the most severe form of malaria—primarily cerebral malaria—die. The committee believes that a better understanding of the disease process will lead to improvements in preventing and treating severe forms of malaria. The committee further believes that determining the indications for treatment of severe malarial anemia is of special urgency given the risk of transmitting the AIDS virus through blood transfusions, the only currently available treatment for malarial anemia. Physicians need to know when it is appropriate to transfuse malaria patients.

The committee recommends greater support for research on the pathogenesis of severe and complicated malaria, on the mechanisms of malarial anemia, and on the development of specific criteria for blood transfusions in malaria.

Social Science Research The impact of drugs to control disease or programs to reduce human-mosquito contact is mediated by local practices and beliefs about malaria and its treatment. Most people in malaria- endemic countries seek initial treatment for malaria outside of the formal health sector. Programs that attempt to influence this behavior must understand that current practices satisfy, at some level, local concerns regarding such matters as access to and effectiveness of therapy, and cost. These concerns may lead to practices at odds with current medical practice. Further, many malaria control programs have not considered the social, cultural, and behavioral dimensions of malaria, thereby limiting the effectiveness of measures undertaken. The committee recognizes that control programs often fail to incorporate household or community concerns and resources into program design. In most countries, little is known about how the demand for and utilization of health services is influenced by such things as user fees, location of health clinics, and the existence and quality of referral services. The committee concludes that modern social science techniques have not been effectively applied to the design, implementation, and evaluation of malaria control programs.

The committee recommends that research be conducted on local perceptions of malaria as an illness, health-seeking behaviors (including the demand for health care services), and behaviors that affect malaria transmission, and that the results of this research be included in community-based malaria control interventions that promote the involvement of communities and their organizations in control efforts.

Innovative Approaches to Malaria Control Malaria control programs will require new ideas and approaches, and new malaria control strategies need to be developed and tested. There is also a need for consistent support of innovative combinations of control technologies and for the transfer of new technologies from the laboratory to the clinic and field for expeditious evaluation. Successful technology transfer requires the exchange of scientific research, but more importantly, must be prefaced by an improved understanding of the optimal means to deliver the technology to the people in need (see Chapter 11 ).

The committee recommends that donor agencies provide support for research on new or improved control strategies and into how new tools and technologies can be better implemented and integrated into on-going control efforts.

Development of New Tools

Antimalarial Immunity and Vaccine Development Many people are able to mount an effective immune response that can significantly mitigate symptoms of malaria and prevent death. The committee believes that the development of effective malaria vaccines is feasible, and that the potential benefits of such vaccines are enormous. Several different types of malaria vaccines need to be developed: vaccines to prevent infection (of particular use for tourists and other nonimmune visitors to endemic countries), prevent the progression of infection to disease (for partially immune residents living in endemic areas and for nonimmune visitors), and interrupt transmission of parasites by vector populations (to reduce the risk of new infections in humans). The committee believes that each of these directions should be pursued.

The committee recommends sustained support for research to identify mechanisms and targets of protective immunity and to exploit the use of novel scientific technologies to construct vaccines that induce immunity against all relevant stages of the parasite life cycle.

Drug Discovery and Development Few drugs are available to prevent or treat malaria, and the spread of drug-resistant strains of malaria parasites is steadily reducing the limited pool of effective chemotherapeutic agents. The committee believes that an inadequate understanding of parasite biochemistry and biology impedes the process of drug discovery and slows studies on the mechanisms of drug resistance.

The committee recommends increased emphasis on screening compounds to identify new classes of potential antimalarial drugs, identifying and characterizing vulnerable targets within the parasite, understanding the mechanisms of drug resistance, and identifying and developing agents that can restore the therapeutic efficacy of currently available drugs.

Vector Control Malaria is transmitted to humans by the bites of infective mosquitoes. The objective of vector control is to reduce the contact between humans and infected mosquitoes. The committee believes that developments are needed in the areas of personal protection, environmental management, pesticide use and application, and biologic control, as well as in the largely unexplored areas of immunologic and genetic approaches for decreasing parasite transmission by vectors.

The committee recommends increased support for research on vector control that focuses on the development and field testing of methods for interrupting parasite transmission by vectors.

Malaria Control

Malaria is a complex disease that, even under the most optimistic scenario, will continue to be a major health threat for decades. The extent to which malaria affects human health depends on a large number of epidemiologic and ecologic factors. Depending on the particular combination of these and other variables, malaria may have different effects on neighboring villages and people living in a single village. All malaria control programs need to be designed with a view toward effectiveness and sustainability, taking into account the local perceptions, the availability of human and financial resources, and the multiple needs of the communities at risk. If community support for health sector initiatives is to be guaranteed, the public needs to know much more about malaria, its risks for epidemics and severe disease, and difficulties in control.

Unfortunately, there is no “magic bullet” solution to the deteriorating worldwide malaria situation, and no single malaria control strategy will be applicable in all regions or epidemiologic situations. Given the limited available financial and human resources and a dwindling pool of effective antimalarial tools, the committee suggests that donor agencies support four priority areas for malaria control in endemic countries.

The committee believes that the first and most basic priority in malaria control is to prevent infected individuals from becoming severely ill and dying. Reducing the incidence of severe morbidity and malaria-related mortality requires a two-pronged approach. First, diagnostic, treatment, and referral capabilities, including the provision of microscopes, training of technicians and other health providers, and drug supply, must be enhanced. Second, the committee believes that many malaria-related deaths could be averted if individuals and caretakers of young children knew when and how to seek appropriate treatment and if drug vendors, pharmacists, physicians, nurses, and other health care providers were provided with up-to-date and locally appropriate treatment and referral guidelines. The development and implementation of an efficient information system that provides rapid feedback to the originating clinic and area is key to monitoring the situation and preventing epidemics.

The committee believes that the second priority should be to promote personal protection measures (e.g., bednets, screens, and mosquito coils) to reduce or eliminate human-mosquito contact and thus to reduce the risk of infection for individuals living in endemic areas. At the present time, insecticide-treated bednets appear to be the most promising personal protection method.

In many environments, in addition to the treatment of individuals and use of personal protection measures, community-wide vector control is feasible. In such situations, the committee believes that the third priority should be low-cost vector control measures designed to reduce the prevalence of infective mosquitoes in the environment, thus reducing the transmission of malaria to populations. These measures include source reduction (e.g., draining or filling in small bodies of water where mosquito larvae develop) or the application of low-cost larval control measures. In certain environments, the use of insecticide-impregnated bednets by all or most members of a community may also reduce malaria transmission, but this approach to community-based malaria control remains experimental.

The committee believes that the fourth priority for malaria control should be higher cost vector control measures such as large-scale source reduction or widespread spraying of residual insecticides. In certain epidemiologic situations, the use of insecticides for adult mosquito control is appropriate and represents the method of choice for decreasing malaria transmission and preventing epidemics (see Chapter 7 and Chapter 10 ).

The committee recommends that support of malaria control programs include resources to improve local capacities to conduct prompt diagnosis, including both training and equipment, and to ensure the availability of antimalarial drugs.

The committee recommends that resources be allocated to develop and disseminate malaria treatment guidelines for physicians, drug vendors, pharmacists, village health workers, and other health care personnel in endemic and non-endemic countries. The guidelines should be based, where appropriate, on the results of local operational research and should include information on the management of severe and complicated disease. The guidelines should be consistent and compatible among international agencies involved in the control of malaria.

The committee recommends that support for malaria control initiatives include funds to develop and implement locally relevant communication programs that provide information about how to prevent and treat malaria appropriately (including when and how to seek treatment) and that foster a dialogue about prevention and control.

Organization of Malaria Control

One of the major criticisms of malaria control programs during the past 10 to 15 years has been that funds have been spent inappropriately without an integrated plan and without formal evaluation of the efficacy of control measures instituted. In many instances, this has led to diminished efforts to control malaria.

The committee strongly encourages renewed commitment by donor agencies to support national control programs in malaria- endemic countries.

The committee recommends that U.S. donor agencies develop, with the advice of the national advisory body, a core of expertise (either in-house or through an external advisory group) to plan assistance to malaria control activities in endemic countries.

The committee believes that the development, implementation, and evaluation of such programs must follow a rigorous set of guidelines. These guidelines should include the following steps:

Identification of the problem

Determine the extent and variety of malaria. The paradigm approach described in Chapter 10 should facilitate this step.

Analyze current efforts to solve malaria problems.

Identify and characterize available in-country resources and capabilities.

Development of a plan

Design and prioritize interventions based on the epidemiologic situation and the available resources.

Design a training program for decision makers, managers, and technical staff to support and sustain the interventions.

Define specific indicators of the success or failure of the interventions at specific time points.

Develop a specific plan for reporting on the outcomes of interventions.

Develop a process for adjusting the program in response to successes and/or failures of interventions.

Review of the comprehensive plan by a donor agency review board

Modification of the plan based on comments of the review board

Implementation of the program

Yearly report and analysis of outcome variables

To guide the implementation of the activities outlined above, the committee has provided specific advice on several components, including an approach to evaluating malaria problems and designing control strategies (the paradigm approach), program management, monitoring and evaluation, and operational research.

Paradigm Approach

Given the complex and variable nature of malaria, the committee believes that the epidemiologic paradigms (see Chapter 10 ), developed in conjunction with this study, may form the basis of a logical and reasoned approach for defining the malaria problems and improving the design and management of malaria control programs.

The committee recommends that the paradigm approach be field tested to determine its use in helping policymakers and malaria program managers design and implement epidemiologically appropriate and cost-effective control initiatives.

The committee recognizes that various factors, including the local ecology, the dynamics of mosquito transmission of malaria parasites, genetically determined resistance to malaria infection, and patterns of drug use, affect patterns of malaria endemicity in human populations and need to be considered when malaria control strategies are developed. In most endemic countries, efforts to understand malaria transmission through field studies of vector populations are either nonexistent or so limited in scope that they have minimal impact on subsequent malaria control efforts. The committee recognizes that current approaches to malaria control are clearly inadequate. The committee believes, however, that malaria control strategies are sometimes applied inappropriately, with little regard to the underlying differences in the epidemiology of the disease.

The committee recommends that support for malaria control programs include funds to permit a reassessment and optimization of antimalarial tools based on relevant analyses of local epidemiologic, parasitologic, entomologic, socioeconomic, and behavioral determinants of malaria and the costs of malaria control.

Poor management has contributed to the failure of many malaria control programs. Among the reasons are a chronic shortage of trained managers who can think innovatively about health care delivery and who can plan, implement, supervise, and evaluate malaria control programs. Lack of incentives, the absence of career advancement options, and designation of responsibility without authority often hinder the effectiveness of the small cadre of professional managers that does exist. The committee recognizes that management technology is a valuable resource that has yet to be effectively introduced into the planning, implementation, and evaluation of most malaria control programs.

The committee recommends that funding agencies utilize management experts to develop a comprehensive series of recommendations and guidelines as to how basic management skills and technology can be introduced into the planning, implementation, and evaluation of malaria control programs.

The committee recommends that U.S. funding of each malaria control program include support for a senior manager who has responsibility for planning and coordinating malaria control activities. Where such an individual does not exist, a priority of the control effort should be to identify and support a qualified candidate. The manager should be supported actively by a multidisciplinary core group with expertise in epidemiology , entomology, the social sciences, clinical medicine, environmental issues, and vector control operations.

Monitoring and Evaluation

Monitoring and evaluation are essential components of any control program. For malaria control, it is not acceptable to continue pursuing a specific control strategy without clear evidence that it is effective and reaching established objectives.

The committee recommends that support for malaria control programs include funds to evaluate the impact of control efforts on the magnitude of the problem and that each program be modified as necessary on the basis of periodic assessments of its costs and effectiveness.

Problem Solving (Operational Research) and Evaluation

At the outset of any malaria prevention or control initiative and during the course of implementation, gaps in knowledge will be identified and problems will arise. These matters should be addressed through clearly defined, short-term, focused studies. Perhaps the most difficult aspects of operational research are to identify the relevant problem, formulate the appropriate question, and design a study to answer that question.

The committee recommends that a problem-solving (operational research) component be built into all existing and future U.S.-funded malaria control initiatives and that support be given to enhance the capacity to perform such research. This effort will include consistent support in the design of focused projects that can provide applicable results, analysis of data, and dissemination of conclusions.

The committee concludes that there is a need for additional scientists actively involved in malaria-related research in the United States and abroad. To meet this need, both short- and long-term training at the doctoral and postdoctoral levels must be provided. This training will be of little value unless there is adequate long-term research funding to support the career development of professionals in the field of malaria.

The committee recommends support for research training in malaria.

Whereas the curricula for advanced degree training in basic science research and epidemiology are fairly well defined, two areas require attention, especially in the developing world: social sciences and health management and training.

The committee recommends that support be given for the development of advanced-degree curricula in the social sciences, and in health management and training, for use in universities in developing and developed countries.

The availability of well-trained managers, decision makers, and technical staff is critical to the implementation of any malaria prevention and control program. The development of such key personnel requires a long term combination of formal training, focused short courses, and a gradual progression of expertise.

The committee recommends support for training in management, epidemiology , entomology, social sciences, and vector control. Such training for malaria control may be accomplished through U.S.-funded grant programs for long-term cooperative relationships between institutions in developed and developing countries; through the encouragement of both formal and informal linkages among malaria- endemic countries; through the use of existing training courses; and through the development of specific training courses.

The committee recommends further that malaria endemic countries be supported in the development of personnel programs that provide long-term career tracks for managers, decision makers, and technical staff, and that offer professional fulfillment, security, and competitive financial compensation.

• Cite this Page Institute of Medicine (US) Committee for the Study on Malaria Prevention and Control; Oaks SC Jr., Mitchell VS, Pearson GW, et al., editors. Malaria: Obstacles and Opportunities. Washington (DC): National Academies Press (US); 1991. 1, Conclusions and Recommendations.
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Erin Brockovich: The Next President Must Address Forever Chemicals

By Erin Brockovich

Ms. Brockovich is an environmental activist.

Every day, I get emails from people asking for help. They think I’m a lawyer. I’m not. They want to know what caused their cancer or why their farm has tested high for chemicals they’ve never heard of. They want someone to fight for them.

The recent Supreme Court decision overturning the 40-year-old Chevron precedent, which allowed federal agencies to interpret the laws they oversee, should wake us up to how truly alone we are when it comes to environmental health protections. If Donald Trump wins in November, things could go from bad to worse. Progress to protect Americans from dangerous chemicals could reach a standstill.

I could list dozens, if not thousands, of contaminants we come in contact with, some regulated by federal and state agencies, and others not. I’ll focus on per- and polyfluoroalkyl substances, or PFAS, a class of thousands of synthetic chemicals that are finally being recognized for the damage they cause.

PFAS are known as “forever chemicals” because they persist in the environment and in human bodies for decades. These chemicals have been used to make common items from textiles to adhesives to food packaging to firefighting foams to nonstick cookware.

The health problems associated with exposure to PFAS include fertility issues, developmental delays in children and increased risk of certain cancers and of obesity, according to the Environmental Protection Agency . Scientists have detected PFAS chemicals in the blood of almost all Americans .

What’s frustrating is that we’ve known for decades which industries use these chemicals, and we’ve known they are accumulating in the environment. But companies and our regulators delayed action.

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