The parasites mainly infest cattle but there have also been dozens of cases involving people.

Parasitic flies have been found in the United States, following an outbreak of screwworm in Central America last year.

New World screwworm myiasis was found in a patient who returned to the US from El Salvador, authorities say.

Mexico reports more than 5,000 cases of screwworm, primarily in cattle and other animals, according to gov’t data.

The parasites mainly infest cattle but there have also been dozens of cases involving people.

Infections have increased by 53% in the past four weeks in Mexico