Sleeping sickness (trypanosomiasis) is a protozoan infection passed to humans through the bite of the tsetse fly. It progresses to death within months or years if left untreated. Near-control of trypanosomiasis was achieved in the 1960s, but the disease has since re-emerged in Sub-Saharan Africa, where political instability and war have hampered public health efforts. As of 2002, the World Health Organization, in conjunction with Médicines Sans Frontièrs (Doctors Without Borders) and major pharmaceutical companies were in the midst of a five-year major effort to halt the spread of trypanosomiasis and treat its victims.

Protozoa are single-celled organisms considered to be the simplest animal life form. The protozoa responsible for sleeping sickness are a flagellated variety (flagella are hair-like projections from the cell which aid in mobility) which exist only in Africa. The type of protozoa causing sleeping sickness in humans is referred...