African Trypanosomiasis or Sleeping Sickness is a parasitic disease transmitted by the tsetse fly. It is endemic in much of Africa and affects both cattle and humans. The prevalence of the disease and the ease of its spread often affects the ability of either humans or cattle to inhabit a given area. The primary symptom of the disease is hypersomnia or excessive sleep, although the disease can also cause insomnia. In all cases, the disease greatly affects brain function and eventually causes severe neurological symptoms before almost inevitably resulting in death.