The New World screwworm infested a human in the U.S. for the first time in years and federal officials are working to prevent it from getting into the food supply.

The first case of a human with a screwworm infection has become a cause for concern for many in the United States. How much of a public health threat is this?

A screwworm is a flesh-eating parasitic blowfly. It lives on the living tissue of warm-blooded animals. It can live in a human, but it is rare.