Life cycle of Clonorchis sinensis and its major endemic regions. Adult flukes in mammalian hosts release eggs via feces. Eggs hatch in snails, develop into cercariae, which encyst as metacercariae in freshwater fish. Human infection occurs through consumption of raw fish. Major endemic areas include China (mainly in Jilin, Guangdong, Guangxi and Heilongjiang), Korea, Vietnam, Eastern Russia and Japan. The red areas (shading) represent the regions endemic for Clonorchis sinensis.