First Human Screwworm Case Confirmed in US

The New World screwworm sounds like something out of a nightmare—and it is officially now in the US. The Department of Health and Human Services on Sunday confirmed the first human case of the flesh-eating parasite in the country, Reuters reports. The case is travel-associated: The Maryland resident had recently returned from traveling to Central America. (Sources initially said the person had been in Guatemala, but the official HHS announcement indicates El Salvador.) The risk to the public is "very low," an HHS spokesperson says, per Axios.

"This is the first human case of travel-associated New World screwworm myiasis (parasitic infestation of fly larvae) from an outbreak-affected country identified in the United States," the statement reads. Decades after it nearly eradicated the parasitic fly, which largely threatens cattle, the US is now fighting to keep it out after it was detected just 700 miles south of Texas and moving north. No cases in animals in the US have been confirmed this year, but the beef industry is on high alert.

The parasitic flies lay eggs in open wounds on any warm-blooded animal, and the hundreds of screwworm larvae that then hatch feed on flesh—and will kill their hosts if not treated. Human infestation is rare, but an outbreak in Texas could cost the state economy $1.8 billion thanks to livestock losses, experts estimate.