Malaria is a mosquito-borne parasitic infection spread by Anopheles mosquitoes. The Plasmodium parasite that causes malaria is neither a virus nor a bacterium – it is a single-celled parasite that multiplies in red blood cells of humans as well as in the mosquito intestine.
When the female mosquito feeds on an infected person, male and female forms of the parasite are ingested along with human blood. The male and female forms of the parasite meet and mate in the mosquito's gut, and the infective forms are passed onto another human when the mosquito feeds again.
Malaria is a significant global problem. In 2015, there were 214 million cases of the disease worldwide, killing about 438,000 people. Malaria is prevalent in Africa, Asia, the Middle East, Central South America, Hispaniola (Haiti and the Dominican Republic), and Oceania (Papua New Guinea, Irian Jaya, and the Solomon Islands). In Canada, malaria is most often caused by travel to and from endemic areas.
Each year, up to 1 million Canadians travel to malaria-endemic areas. This results in 350 to 1,000 annual cases of malaria in Canada and 1 to 2 deaths per year.
The parasite has progressively developed resistance to many anti-malarial medications, and in several areas of the world, especially southeast Asia, resistance to all anti-malarial drugs has been reported.
There are 4 species of the Plasmodium parasite that can cause malaria in humans: P. falciparum, P. vivax, P. ovale, and P. malariae. The first 2 types are the most common. Plasmodium falciparum is the most dangerous of these parasites; infection with it can kill rapidly (within several days), whereas the other species cause illness but usually not death. Falciparum malaria is particularly frequent in sub-Saharan Africa and Oceania.