Human African trypanosomiasis or sleeping sickness is a widespread tropical disease that can be fatal if not treated. It is spread by the bite of an infected tsetse fly (Glossina Genus). The tsetse fly bite erupts into a red sore and within a few weeks the person can experience fever, swollen lymph glands, aching muscles and joints, headaches and irritability. In advanced stages, the disease attacks the central nervous system, causing changes in personality, alteration of the biological clock (the circadian rhythm), confusion, slurred speech, seizures, and difficulty walking and talking. These problems can develop over many years in the Gambiense form and some months in the Rhodesiense form; if not treated, the person will die. Control of sleeping sickness is based on reduction of the reservoirs of infection by early diagnosis and control of tsetse flies.