article_snippet: Malaria is spread by blood sucking female mosquitoes like the Anopheles stephensi mosquito shown above .
article_snippet: Malaria is one of the world's biggest infectious killers, infecting around 200 million people every year and claiming the lives of more than 500,000.
article_snippet: Not all Plasmodium parasites cause malaria in humans.
article_snippet: One, known as Plasmodium falciparum, is responsible for most of the deaths while others like Plasmodium malariae cause a milder form of the disease.
article_snippet: Plasmodium knowlesi rarely cause malaria in humans while other strains of the parasite only infect primates, other mammals or birds.
article_snippet: Plasmodium falciparum is known to have been in existence for up to 100,000 years, but the population size did not increase until around 10,000 years ago.
article_snippet: Plasmodium falciparum is thought that the disease may have originally evolved in gorillas and then passed to humans, but the evidence for this is inconclusive.