The first human case of the flesh-eating parasite, New World Screwworm, has been detected in the United States

The U.S. has confirmed its first human case of a flesh-eating parasite, the Department of Health and Human Services (HHS) said Monday.

The infection was caused by the New World screwworm (NWS), a parasitic fly species whose larvae burrow into the flesh of living hosts using sharp mouth hooks, destroying tissue and often leading to death in untreated cases.

According to HHS, the patient was a Maryland resident who had recently returned from El Salvador. State health officials said the patient has since fully recovered and emphasized there is no evidence of further spread. HHS also stressed that the risk to the U.S. public remains very low.

The parasite is already a significant problem in livestock across parts of Central America and Mexico. In Panama, screwworm infections among animals surged from an average of 25 cases a year to over 6,500 in 2023, according to the U.S. Department of Agriculture (USDA). Since then, outbreaks have been reported in seven other Central American countries, breaking through a decades-old barrier that had kept the pest contained to South America.

While screwworm has not been detected in U.S. animals, the USDA noted it had been eradicated domestically for decades through a sterilization program in which male flies were released to collapse breeding cycles. Still, given the parasite’s northward spread, the USDA warned NWS poses a serious threat not only to U.S. ranchers and livestock, but also to the nation’s food security and national security. The agency outlined new prevention measures to stop the pest from crossing into the U.S.