Flesh-Eating Screwworm Detected 25 Miles from US Border, USDA Says

A flesh-eating New World screwworm has been detected in Mexico just 25 miles from the United States border, marking the closest approach to U.S. soil since at least last September, according to the U.S.

Department of Agriculture (USDA). Federal data shows that U.S.

officials have tracked 32 cases of the parasitic fly throughout the Mexican state, including 19 active cases. Overall, at least 26,216 screwworm cases have been identified across Mexico, with upward of 2,700 remaining active, the USDA said.

In recent months and years, the parasite has appeared closer to the U.S. than ever before.

In April, Texas Agriculture Commissioner Sid Miller announced it had been found at a location in Mexico that was 60 miles from the U.S. Texas officials have warned outdoor enthusiasts about the parasite since late 2024, when the state's Parks and Wildlife Department issued an advisory stating the screwworm had recently been detected in a cow in southern Mexico.

Last year, the first case of a New World screwworm infestation in a human was confirmed in the U.S., the Department of Health and Human Services announced. The case was detected in a traveler who had returned to Maryland from El Salvador, HHS spokesperson Andrew Nixon told CBS News in a statement.

Maryland health officials later said the person had recovered, and investigators found no evidence of transmission to other people or animals. The New World screwworm is a parasitic fly that feeds on warm-blooded animals and people.

It lays its eggs in open wounds or orifices such as the eyes, ears, nose, or mouth, which can then eat living tissue or flesh once they hatch, according to the Centers for Disease Control and Prevention (CDC). The screwworm is typically found in South America and parts of the Caribbean, but it has been detected farther north in Central America and Mexico over the last three years, the CDC said.