Malaria is caused by the unicellular Plasmodium parasite. The parasites enter the human blood stream after the bite of a bloodsucking Anopheles mosquito. The parasite undergoes different life cycles in humans and mosquito. Out of the five Plasmodium species that infect humans Plasmodium falciparum causes the most serious courses of the disease. Typical symptoms are recurrent fever, chills and stomach and intestinal complaints. Malaria is endemic in about 100 countries. Children under five years of age are at the highest risk of dying of malaria.