Malaria is a disease caused by a parasite transmitted via the bites of infected Anopheles mosquitoes. The parasite infects and multiplies in the liver and blood cells of humans, causing symptoms including fever, chills, and vomiting. Malaria was responsible for approximately 781,000 deaths worldwide in 2009, mostly among African children. It is most prevalent in tropical and subtropical regions of the world, including parts of Africa, Asia, and South America.