Malaria

Malaria is a mosquito-borne infectious disease which is transmitted by the bite of Anopheles mosquitoes. Human malaria causes symptoms that typically include fever, fatigue, vomiting, and headaches; in severe cases, it can cause jaundice, seizures, coma, or death. Symptoms usually begin 10 to 15 days after being bitten by an infected Anopheles mosquito. If not properly treated, people may have recurrences of the disease months later. Those who survive an infection develop partial immunity, being susceptible to reinfection although with milder symptoms. This partial resistance disappears over months to years if the person has no continuing exposure to malaria.

Malaria is caused by single-celled parasites of the genus Plasmodium, generally spread through the bites of an infected female Anopheles mosquito. The mosquito bite introduces the parasites from the mosquito's saliva into the blood. The parasites initially reproduce and mature in the liver without causing symptoms. After a few days the mature parasites spread into the bloodstream, where they infect and destroy red blood cells, causing the symptoms of infection. Five species of Plasmodium commonly infect humans. The three species associated with more severe cases are P. falciparum (which is responsible for the vast majority of malaria deaths), P. vivax, and P. knowlesi (a simian malaria that spills over into thousands of people a year). P. ovale and P. malariae generally cause a milder form of malaria. Malaria is typically diagnosed by the microscopic examination of blood using blood films, or with antigen-based rapid diagnostic tests. Methods that use the polymerase chain reaction to detect the parasite's DNA have been developed, but they are not widely used in areas where malaria is common, due to their cost and complexity.

The risk of disease can be reduced by preventing mosquito bites through the use of mosquito nets and insect repellents or with mosquito-control measures such as spraying insecticides and draining standing water. Several prophylactic medications are available to prevent malaria in areas where the disease is common. As of 2023, two malaria vaccines have been endorsed by the World Health Organization. Resistance among the parasites has developed to several antimalarial medications; for example, chloroquine-resistant P. falciparum has spread to most malaria-prone areas, and resistance to artemisinin has become a problem in some parts of Southeast Asia. Because of this, drug treatment for malaria infection should be tailored to best fit the Plasmodium species involved and the geographical location where the infection was acquired.

The disease is widespread in the tropical and subtropical regions that exist in a broad band around the equator. This includes much of sub-Saharan Africa, Asia, and Latin America. In 2023, some 263 million cases of malaria worldwide resulted in an estimated 597,000 deaths. Around 95% of the cases and deaths occurred in sub-Saharan Africa. Malaria is commonly associated with poverty and has a significant negative effect on economic development; in Africa, it is estimated to result in economic losses (estimated at US$12 billion a year in 2005) due to increased healthcare costs, lost ability to work, and adverse effects on tourism.