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.