Malaria Malaria is caused by a mosquito-borne, protozoan parasite belonging to the genus Plasmodium. Of the five species of Plasmodium that infect humans, Plasmodium falciparum is the most deadly and is responsible for the majority of malaria disease and death. Every year, falciparum malaria causes disease in hundreds of millions of people living in the tropics and subtropics, killing a million or more according to some estimates. The vast majority of these deaths occur in sub-Saharan Africa, mostly among young children and infants. When treated with effective antimalarial drugs, malaria can be cured completely.