Malaria

Overview

Malaria spreads through the bites of female Anopheles mosquitoes, which transmit infectious Plasmodium parasites into humans. The disease most often strikes during rainy periods in endemic regions. The burden of malaria falls hardest on Sub-Saharan Africa.

Malaria is difficult to control largely because both the mosquito vectors and the parasites adapt over time. Effective tools exist to combat the disease, but parasites and mosquitoes will eventually develop ways to resist those tools if they are used in isolation or used ineffectively. Sustainable control requires a combination of new approaches, and research plays a critical role in developing next-generation strategies.

Signs and Symptoms

Malaria produces two general patterns of illness: uncomplicated malaria and severe malaria.

Uncomplicated malaria involves recurring episodes of:

• Chills and intense fever
• Sweating
• Headache
• Muscle aches and fatigue
• Nausea, vomiting, and diarrhea
• Malaise and body aches

Severe malaria can include:

• Cerebral malaria and coma
• Seizures
• Severe anemia
• Respiratory distress
• Kidney and liver failure
• Cardiovascular collapse and shock

Related Health Effects

Untreated malaria can progress rapidly to severe disease and death. Neurological complications can occur in severe cases, most commonly in young children. In children with cerebral malaria, brain swelling can cause seizures, coma, and death.

Malaria also contributes to malnutrition in children, which is an underlying factor in many deaths among young children worldwide. In malaria-endemic regions, many cases of severe maternal anemia and some cases of low-birthweight babies are linked to malaria. Malaria causes many stillbirths each year. 

Long-term impacts include death, disability, and significant socioeconomic burden on societies where the disease is prevalent.

Causes and Risk Factors

Malaria can be caused by several species of Plasmodium parasites, each of which has a complex life cycle. Female mosquitoes of the genus Anopheles transmit malaria parasites to human hosts. A diverse group of 30 Anopheles species serves as vectors of human disease. Several physiological, behavioral, and ecological characteristics determine how effective various Anopheles species are as vectors of malaria.

The interaction between the Plasmodium parasite and the host immune system during infection strikes a delicate balance. The relationship can produce protective immunity or trigger harmful immune responses. The complex natures of both the malaria parasite and the human immune response have made it difficult to understand the mechanisms of protection or disease in humans.

Children and pregnant women face a higher risk of severe disease. In many endemic regions, malaria cases increase during rainy periods when mosquito breeding sites are more abundant.

Prevention Guidance

Vaccines to prevent malaria are now approved for ages 5 to 30 months in infants and young children in Africa. However, vaccine efficacy wanes over time, underscoring the need for new vaccines or other interventions that offer high-level protection against disease. These include next generation vaccines that will have higher and more durable efficacy across all ages. These will be critical for improving malaria control, prevention, and elimination efforts.

Several additional candidate vaccines that target various life cycle stages of the malaria parasite are in development. NIH is also exploring novel vaccine strategies, such as transmission-blocking vaccines, which work by blocking transmission of the malaria parasite to the mosquito vector. NIH has also developed monoclonal antibodies that can provide high-level protection across all ages for up to 6 months. This new approach may have broad application in Africa as well as in U.S. citizens who may be traveling to Africa.

Vector management tools such as insecticides, environmental modification, and bed nets have contributed greatly to successful malaria control efforts historically. However, these tools have faced setbacks in recent years due to factors such as the emergence of insecticide resistance in mosquitoes. NIH supports research on new vector management strategies to prevent parasite transmission and reduce the mosquito population.

Travelers to countries where malaria is present should follow official recommendations to reduce their risk of contracting the disease. Do not rely on unproven natural approaches.

To reduce the risk of mosquito bites, travelers can take these steps:

• Wear protective clothing.
• Sleep in a screened or air-conditioned room with windows closed.
• Use a bed net if outdoors.
• Use an EPA-registered insect repellent.

Epidemiological data are critical to developing novel vaccines and drugs and to implementing effective control and prevention programs.

Diagnosis

Diagnostic tools for malaria currently include:

• Microscopic analysis
• Rapid diagnostic testing

Microscopic analysis of blood smears remains a key technique for diagnosing malaria and is often regarded as the laboratory gold standard, but it is labor-intensive and requires highly trained technicians. It can be time-consuming, variable in quality, difficult to use in resource-poor field settings, and cannot directly detect drug resistance. Rapid diagnostic tests are now widely used to provide prompt, parasite-based diagnosis in many settings where good-quality microscopy is not available.

Treatment and Management

Antimalarial drugs and mosquito control programs help control malaria in endemic areas and have reduced the geographic range of malarial disease worldwide. However, drug-resistant parasites have emerged and spread, contributing to stalled progress in malaria control, and the need for new, effective drugs remains a critical priority on the global malaria research agenda.

NIH-supported researchers seek to understand the molecular biology of the Plasmodium parasite and how it interacts with its human host at each stage of the parasite’s life cycle. Using that information, scientists hope to identify mechanisms of emerging drug resistance and to develop new drugs that block molecular processes required for parasite survival.

Taking vitamin A and zinc supplements may help improve malaria symptoms, but only in malnourished children, studies suggest. There is no evidence that travelers should take vitamin A or zinc to prevent or treat malaria.

Find Clinical Trials

Clinical trials uncover better ways to prevent, diagnose, treat, and understand diseases and conditions. To ensure results apply to everyone, volunteers of all ages, sexes, and backgrounds, including both healthy individuals and those with specific medical conditions, are needed. Find clinical trials on malaria.

Research Information

The National Institutes of Health (NIH) is the largest public funder of biomedical research in the world. NIH invests most of its budget in medical research seeking to enhance life and to reduce illness and disability. NIH-funded research has led to breakthroughs and new treatments helping people live longer, healthier lives, and building the research foundation that drives discovery.

NIH is the lead agency in the U.S. federal government supporting malaria research and development. The institute has a longstanding commitment to malaria research to support the goals of reducing illness and death from malaria and ultimately eradicating the disease. NIH is one of the largest funders of basic malaria research globally.

The NIH Malaria Research Program covers the full cycle of malarial disease, from parasite to mosquito to human host. Research in recent decades has shed light on many aspects of Plasmodium biology, broadening understanding of how parasites interact with the human immune system, cause human disease, and are transmitted by mosquitoes.

NIH-supported researchers have contributed to multiple genomic sequencing efforts for various parasite isolates, notably of Plasmodium falciparum, the deadliest malaria parasite, and Plasmodium vivax, the most widespread malaria parasite, as well as of other Plasmodium species. Similarly, NIH-supported researchers have contributed genomic sequencing efforts for various Anopheline mosquito species, including Anopheles gambiae, a major malaria vector.

Since 2010, NIH has established more than 10 International Centers of Excellence for Malaria Research (ICEMRs) spanning all malaria-endemic continents. The ICEMRs have had many achievements, including the sequencing of 185 Plasmodium vivax genomes, the development of a test kit to detect fake or substandard artemisinin drugs, and characterization of drug-resistant malaria and insecticide-resistant mosquitoes in different parts of the world.

NIH also supports research to develop easy-to-use tests that diagnose the malaria parasite causing an infection and identify its drug resistance profile.

Find NIH-funded research projects using NIH RePORTER, a searchable database of current and past research projects supported by NIH and other federal agencies.