The control of malaria has proved elusive, and an estimated 60 million cases of the disease occur worldwide each year.
Malaria is now on the increase throughout the tropics, especially on the Indian subcontinent.
Imported cases occur among persons traveling from endemic areas to temperate zone countries. Although transmission in the United States via mosquito bite is rare, there is justified concern about outbreaks of malaria in places that are appropriate habitats for anopheline mosquitoes, such as California. Thus, when instituting antimalarial therapy in such individuals, the physician should be aware that this resistant form may be present. The sporozoites of the protozoan enter the human host via the bite of an infected female anopheline mosquito. The parasites' progeny are released from ruptured hepatocytes and invade red blood cells to initiate the erythrocytic phase.