Humans are infected with malaria by the bite of anophelene mosquitos carrying plasmodia sporozoites. These sporozoites pass quickly from the blood into hepatocytes, where they develop into mature liver-stage parasites over several days. The clinical stage of the illness begins only when the liver-stage parasites rupture into the bloodstream and erythrocytes are invaded. The pre-erythrocytic stages of malaria are inviting targets for vaccine development, because an effective immune response to these early stages would prevent symptomatic infections.
