<p>Malaria is caused by infection with protozoan parasites of the Plasmodia genus; the four species which are important in human disease are Plasmodium falciparum, P. vivax, P. ovale and P. malariae. The parasites (known as sporozoites at this stage) enter the bloodstream through the bite of a female Anopheles mosquito. They migrate to the liver, where they infect hepatocytes. They then undergo schizogony (divide and multiply) for a couple of weeks. The infected cells then rupture, releasing parasites which invade erythrocytes, and, again mature, divide and multiply until eventually the erythrocyte ruptures, releasing fresh parasites. Repeated cycles of this process of invasion and rupture of erythrocytes are responsible for the cyclical clinical symptoms seen with malaria (chills, fever, rigors). Other symptoms common to all types of malaria include anaemia, jaundice, splenomegaly and hepatomegaly. In P. vivax or P. ovale infection some of the parasites may persist in the hepatic stage for years, and cause relapses. P. falciparum, responsible for the most severe form of malaria, can be fatal, particularly if cerebral malaria develops.</p>