Because in fish, there are various fungi and parasites, among which Clonorchis sinensis is the most. This insect is especially parasitic in freshwater fish. If you eat raw fish or half-cooked fish with bloodshot blood, clonorchiasis will enter the human body with the fish and parasitize in the human liver and bile duct, causing chronic parasitic diseases. In addition, liver flukes often re-enter the water with human excrement after spawning, and will immediately get into the fish once there is an opportunity, forming a vicious circle. People often eat sashimi porridge, which is to pour hot porridge on sashimi. Fish fillets are only heated at high temperature for a short time and will not kill insects. In addition, sashimi marinated with ginger, vinegar and wine is also marinated for a short time. Seasoning is ok, but it can't kill clonorchiasis. People are easily infected with clonorchiasis after eating, and are prone to chronic cholangitis, cholecystitis, hepatomegaly and pain, emaciation, anemia, insomnia and other symptoms.
There are few liver flukes in marine fish, and the probability of causing disease is small when eaten raw, but it is still not common. Freshwater fish cannot be eaten raw.