The United States has reported its first human case of New World screwworm, a parasite infamous for eating living flesh. The patient, who returned from El Salvador to Maryland, developed painful, foul-smelling wounds infested with larvae.

Screwworm flies lay eggs in open wounds, and the larvae feed on living tissue for days before maturing. In humans, infestations can cause fever, swelling, severe pain, and even death if untreated. In cattle, the damage can be devastating, especially in newborn calves.

What worries experts is the parasite’s ability to spread rapidly. Adult flies can travel miles, and outbreaks have already moved north through Mexico. The US cattle industry, worth billions, is on high alert.

To fight back, the US Department of Agriculture is setting up a sterile fly facility in Texas, a strategy that once wiped out screwworm in the 1960s. But with cases edging closer to the border, fears remain: could this parasite make a comeback in America?