Health officials confirm that a Maryland resident was diagnosed with New World screwworm earlier this month after traveling to El Salvador. It has been declared the first human case in the United States by the Centers for Diesease Control and Prevention.

The first human screwworm case in the U.S. has been traced to a person in Maryland who traveled from Guatemala.

The parasite — the larvae of the new world screwworm fly — can devastate cattle herds and is rife in parts of Central America.