Malaria

Malaria is a mosquito-borne infectious disease that affects vertebrates and 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. In those who have recently survived an infection, reinfection usually causes milder symptoms. This partial resistance disappears over months to years if the person has no continuing exposure to malaria. The mosquitoes themselves are harmed by malaria, causing reduced lifespans in those infected by it.

Malaria is caused by single-celled eukaryotes of the genus Plasmodium. It is spread exclusively through bites of infected female Anopheles mosquitoes. The mosquito bite introduces the parasites from the mosquito's saliva into the blood. The parasites travel to the liver, where they mature and reproduce. 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 medications are available to prevent malaria for travellers in areas where the disease is common. Occasional doses of the combination medication sulfadoxine/pyrimethamine are recommended in infants and after the first trimester of pregnancy in areas with high rates of malaria. As of 2023, two malaria vaccines have been endorsed by the World Health Organization. The recommended treatment for malaria is a combination of antimalarial medications that includes artemisinin. The second medication may be either mefloquine (noting first its potential toxicity and the possibility of death), lumefantrine, or sulfadoxine/pyrimethamine. Quinine, along with doxycycline, may be used if artemisinin is not available. In areas where the disease is common, malaria should be confirmed if possible before treatment is started due to concerns of increasing drug resistance. 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.

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. Rates of disease decreased from 2010 to 2014, but increased from 2015 to 2021. According to UNICEF, nearly every minute, a child under five died of malaria in 2021, and "many of these deaths are preventable and treatable". Malaria is commonly associated with poverty and has a significant negative effect on economic development. In Africa, it is estimated to result in losses of US$12 billion a year due to increased healthcare costs, lost ability to work, and adverse effects on tourism. The malaria caseload in India decreased by 69% from 6.4 million cases in 2017 to two million cases in 2023. Similarly, the estimated malaria deaths decreased from 11,100 to 3,500 (a 68% decrease) in the same period.

The term malaria originates from Medieval Italian: mala aria 'bad air', a part of miasma theory; the disease was formerly called ague or marsh fever due to its association with swamps and marshland. The term appeared in English at least as early as 1768. Malaria was once common in most of Europe and North America, where it is no longer endemic, though imported cases do occur. The scientific study of malaria is called malariology.

Adults with malaria tend to experience chills and fever, classically in periodic paroxysmal attacks lasting around six hours, followed by a period of sweating and fever relief—as well as headache, fatigue, abdominal discomfort, and muscle pain. Children tend to have more general symptoms: fever, cough, vomiting, and diarrhea.

Initial manifestations of the disease—common to infection with all malaria parasite species—are similar to flu-like symptoms, and can resemble other conditions such as sepsis, gastroenteritis, and viral diseases. The presentation may include headache, fever, shivering, joint pain, vomiting, hemolytic anemia, jaundice, hemoglobin in the urine, retinal damage, and convulsions.

The classic symptom of malaria is paroxysmal attacks—a cyclical occurrence of sudden coldness followed by shivering and then fever and sweating, occurring every two days (tertian fever) in P. vivax and P. ovale infections, and every three days (quartan fever) for P. malariae. P. falciparum infection can cause recurrent fever every 36–48 hours, or a less pronounced and almost continuous fever.