“If worms in fish posed a serious health hazard, one would have expected that Japan, a country in which raw fish are consumed in huge quantities, would have seen severe health effects.”
Actually there is a health problem with raw fish. Uncooked pupae of the worms can hatch in humans and the worm can enter internal organs and wreack havoc. if the person is lucky it will enter flesh and the area can be painful but the worm can be removed.In England the sushi bars have to deep freeze the fish before serving so that the eggs and pupae are killed.