Sleeping sickness is caused by two parasites Trypanosoma brucei gambiense and Trypanosoma brucei rhodiense which are transmitted by tsetse flies. The disease infects the brain and death can ensue within a few months if not treated.
African trypanosomiasis was endemic in 36 African countries. By 1993, there were 25,000 to 50,000 cases per year and about 25,000 deaths. The population infected numbers over 100,000, and about 50 million people are at risk of becoming infected.