Malaria is a serious, sometimes fatal, disease caused by a parasite. Malaria occurs in over 100 countries and territories. The World Health Organization estimates that yearly 300-500 million cases of malaria occur and more than 1 million people die of malaria. About 1,200 cases of malaria are diagnosed in the United States each year.
Humans get malaria from the bite of a malaria-infected mosquito.
When a mosquito bites an infected person, it ingests microscopic malaria parasites found in the person s blood. The malaria parasite must grow in the mosquito for a week or more before infection can be passed to another person. If, after a week, the mosquito then bites another person, the parasites go from the mosquito s mouth into the person s blood. The parasites then travel to the person s liver, enter the liver s cells, grow and multiply. During this time when the parasites are in the liver, the person has not yet felt sick.