U.S. confirms nation's first travel-associated human screwworm case connected to Central American outbreak

The U.S. Department of Health and Human Services has confirmed the nation’s first travel-associated case of New World screwworm in a human, linked to the ongoing outbreak in Central America, according to a statement provided to Reuters.

The case, verified by the CDC on August 4, involved a patient who had recently returned from El Salvador, an HHS spokesperson said. Maryland health officials and the CDC conducted the investigation.

Screwworms are parasitic flies that lay eggs in wounds of warm-blooded animals, including humans. Once hatched, larvae burrow into living tissue, and untreated infestations can be fatal. Human cases are rare but possible.

The CDC emphasized that the public health risk in the U.S. is “very low.” No animal cases have been reported domestically this year.

Industry sources previously told Reuters that the infected traveler had come from Guatemala, highlighting discrepancies that could fuel concern among cattle producers already on edge. Screwworm outbreaks pose a severe economic threat to U.S. livestock, with USDA estimates suggesting a potential $1.8 billion impact in Texas alone if the pest spreads.

The USDA is accelerating efforts to combat screwworm, including plans for a new sterile-fly production facility in Texas—a key component of eradication strategies historically used in the 1960s.

Screwworms have been advancing north from Central America through Mexico since 2023. Recent cases were detected in Veracruz, Mexico, prompting U.S. border restrictions on cattle imports.

Original article here: https://www.reuters.com/business/environment/us-confirms-nations-first-travel-associated-human-screwworm-case-connected-2025-08-25/