Tsetse flies transmit a parasite which replicates in the mammalian bloodstream and eventually invades the brain to cause death. The disease, commonly known as sleeping sickness, is endemic in sub-Saharan Africa. It is a threat to humans and animals, often infecting the domestic animals that villagers depend upon for their survival. A laboratory at the School—one of only a handful in the world—breeds tsetse flies in order to genetically modify its beneficial symbiotic bacteria to aid the tsetse fly in feeding off the blood of its host. By placing the genetically modified bacteria back into the tsetse fly, researchers hope to stop the transmission of the disease. Faculty are working to control many infectious diseases, including Hepatitis C, Lyme disease, West Nile virus, and Chlamydia.