Schistosomiasis (Bilharzia)
This disease occurs in the central Yangzi River (Cháng Jiāng) basin, carried in water by minute worms that infect certain varieties of freshwater snail found in rivers, streams, lakes and, particularly, behind dams. The infection often causes no symptoms until the disease is well established (several months to years after exposure); any resulting damage to internal organs is irreversible. Effective treatment is available.