Fish carry many types of worms. Flukes, anasakis, tapeworms, and many other types that supposedly don't infect humans. All fish has worms. They are tiny and in between the flakes of the fish. You have to hold the fish up to a light to see them. The fast food places that sell fish actually soak the fish in some sort of liquid in a bucket that makes the worms come out. After learning this I can't eat it anymore.