Human African trypanosomiasis (HAT), also known as sleeping sickness, is a severe and sometimes fatal disease caused by infection with the trypanosomes Trypanosoma brucei gambiense (West Africa) and Trypanosoma brucei rhodesiense (East Africa). It is transmitted during the bite of the tsetse fly of the genus Glossina; these flies are mostly active during the daytime. HAT is endemic or epidemic in most countries of sub-Saharan Africa. The disease is found mainly in rural areas.

Transmission and disease prevalence correlate with vector control programs, health care infrastructure, fly density, infection rates of tsetse flies, and human-fly contact. Typically, these all negatively correspond with periods of civil unrest. Animal and human reservoirs have been implicated in epidemics.

West African sleeping sickness (Gambian) and East African sleeping sickness (Rhodesian) present somewhat differently.

West African sleeping sickness (Gambian): Characterized by slow, chronic progression of emaciation, ultimately leading to somnolence and mental deterioration over months to years. Initially, an inflammatory skin lesion (trypanosome chancre) is seen in 30% of patients at the site of the bite. A macular or urticarial eruption can be seen 6-8 weeks later in association with fever, headache, and malaise. Facial and peripheral edema are frequently noted, as is posterior cervical lymphadenopathy (Winterbottom's sign). Over 2-3 years, slow central nervous system (CNS) deterioration is noted with weakness, apathy, malaise, somnolence, coma, and death ensuing.

East African sleeping sickness (Rhodesian): Characterized by a more rapid course of fevers, chills, and anemia, ultimately ending in encephalopathy and death within a few months. Initially, a trypanosome chancre is seen (50%). Cervical lymphadenopathy is less common, but a macular eruption may accompany fever, malaise, and headache within 2-3 weeks. Sleep alteration and CNS decline ensue within 3 months and are usually fatal if untreated.

Related topic: American trypanosomiasis