US health officials have confirmed a human case of the deadly cattle screwworm parasite, marking the first such detection linked to the recent outbreak in Central America. The parasite, known for its flesh-eating larvae, poses serious health risks and has raised concerns about potential spread within the United States. The patient had recently returned to Maryland from El Salvador.

Officials from the Maryland Department of Health and the Centers for Disease Control and Prevention identified the parasite as a New World screwworm, noting that the case is linked to travel.

Although the risk of contracting the parasite in the United States remains low, it’s important to understand the New World screwworm. The larvae of these flies feed on living tissue, primarily affecting animals and livestock, though humans can also become infested.


While the fly was eliminated in the US during the 1960s and in Mexico in the 1970s, recent cases have been reported in Panama, Costa Rica, Nicaragua, and Honduras, despite the parasite having been eradicated in Central America in the early 2000s.

In the mid-20th century, US officials successfully eradicated the screwworm by deploying planes to release sterile flies over infestation zones, Reuters reported.

Raises concerns for US cattle industry

Travel-related cases of the flesh-eating New World screwworm parasite pose little danger to the general public, and US officials have not confirmed any infestations in animals so far in 2025.

Still, the discovery of a human case is alarming for cattle ranchers, beef producers, and livestock traders. The parasite, recently spreading north from Central America into southern Mexico, has heightened fears that it could eventually reach the United States.

If an outbreak were to occur domestically, experts warn it could devastate cattle populations and drive beef prices, already at record highs, even higher.

How to stay safe

To curb the threat of a potential outbreak, the US Department of Agriculture plans to construct a facility in Texas, the nation’s largest cattle-producing state, to breed and release sterile flies in an effort to suppress screwworm populations.