Definition of Sleeping sickness:

Sleeping sickness is infection with germs carried by certain flies. It results in swelling of the brain.

Causes, incidence, and risk factors:

Sleeping sickness is caused by two germs, Trypanosoma brucei rhodesiense and Trypanosomoa brucei gambiense. The more severe form of the illness is caused by T. rhodesiense.

Tsetse flies carry the infection. When an infected fly bites you, the infection spreads through your blood.

Risk factors include living in parts of Africa where the disease is found and being bitten by tsetse flies. The disease is very rare in the United States, and is only found in travelers who have visited or lived in Africa.