Colored transmission electron micrograph (TEM) of a section through a red blood cell infected with malarial parasites (Plasmodium sp.). Single-celled malaria parasites are in the swollen part of the blood cell (green). These plasmodia are spread to humans by tropical species of mosquito (Anopheles sp.). Once in the human body, the plasmodia spread to the liver and then the blood, where they multiply inside blood cells bursting out when mature to reinfect other blood cells. Release of plasmodia into the blood causes bouts of fever in malaria that can be fatal. Magnification unknown.