On Aug. 24, 2025, the U.S. Department of Health and Human Services reported the first human case in the United States of travel-associated New World screwworm, a flesh-eating parasite, from an outbreak-affected country.

The case, investigated by the Maryland Department of Health and the U.S. Centers for Disease Control and Prevention (CDC), was confirmed by the CDC as New World screwworm on August 4, and involved a patient who returned from travel to El Salvador, HHS spokesman Andrew G. Nixon said in an email to Reuters.

The differing accounts from the U.S. government and industry sources on the human case are likely to further rattle an industry of cattle ranchers, beef producers and livestock traders already on high alert for potential U.S. infestations as screwworm has moved northward from Central America and southern Mexico.

The USDA has estimated a screwworm outbreak could cost the economy in Texas, the biggest U.S. cattle-producing state, about $1.8 billion in livestock deaths, labor costs and medication expenses.

The sole operating plant is in Panama City and can produce a maximum of 100 million sterile screwworm flies each week. The USDA has estimated that 500 million flies would need to be released weekly to push the fly back to the Darien Gap, the stretch of rainforest between Panama and Colombia.