The known geographical distribution of schistosomiasis in East Africa. The geographical distribution of (A) Schistosoma haematobium and (B) S. mansoni infection, based on available survey collected between 1980 and 2009, and categorized according to WHO prevalence thresholds (n = 2,405). First-level administrative boundaries are indicated in grey. S. mansoni infection is most prevalent around Lake Victoria basin, North-west Uganda and the central highlands of Kenya. In contrast, S. haematobium infection is distributed along the Kenyan and Tanzanian coast, Tana River in Kenya and Lake Victoria in Kenya and Tanzania, but absent from Uganda.