Malaria merozoites (green/purple) invading red blood cells (red), illustration. Merozoites are covered in a fuzzy coating of surface proteins (light blue) that are shed during invasion. In humans malaria is caused by Plasmodium sp. parasites, which are transmitted into the bloodstream by bites from infected mosquitos (Anopheles sp.). After infection, the parasites travel through the bloodstream to the liver. There, they mature into merozoites, which enter the bloodstream and infect red blood cells. The merozoites replicate inside the red blood cells, destroying them upon release, and then infect more. Most symptoms are caused by this process, and include fever, shaking chills, headache, muscle aches, tiredness and other flu-like symptoms.