Five species of the plasmodium parasite can infect humans: the most serious forms ofthe disease are caused by Plasmodium falciparum. Malaria caused by Plasmodium vivax, Plasmodium ovale and Plasmodium malariae causes milder disease in humans that is not generally fatal. A fifthspecies, Plasmodium knowlesi, is a zoonosis that causes malaria in macaques but can also infect humans.
Malaria transmission can be reduced by preventing mosquito bites by distribution ofinexpensive mosquito nets and insect repellents, or by mosquito-control measures such as spraying insecticides inside houses and draining standing water where mosquitoes lay their eggs. Although many are underdevelopment, the challenge of producing a widely available vaccine that provides a high level of protection for a sustained period is still to be met.
A variety of antimalarial medication areavailable. In the last 5 years, treatment of P. falciparum infections in endemic countries has been transformed by the use of combinations of drugs containing an artemisinin derivative. Severe malaria istreated with intravenous or intramuscular quinine or, increasingly, the artemisinin derivative artesunate. Several drugs are also available to prevent malaria in travellers to malaria-endemiccountries (prophylaxis). Resistance has developed to several antimalarial drugs, most notably chloroquine.
Each year, there are more than 250 million cases of malaria, killing between one and...