Those ten percent can be the host to one of the four kinds of parasites that cause malaria. The most dangerous of these parasites is called Plasmodium falciparum. A plasmodium is a one celled organism. The word falciparum comes from two Greek words: one means "sickle–shaped" and the other means "birth" or "multiple births."

Plasmodium falciparum does indeed have many "births" as it moves back and forth from human and animal hosts to mosquitoes and back again–each serving as a host to the disease that causes severe illness and even death. A host is an animal or plant that supports a parasite and allows it to grow, even if doing so causes the animal or plant great harm.