A person in Maryland has been diagnosed with a rare flesh-eating parasite known as the New World screwworm after traveling from Guatemala, marking the first confirmed human case in the US. The New World screwworm, a fly whose larvae burrow into living tissue, primarily affects cattle and other warm-blooded animals but can also infect people in rare cases. It causes severe, sometimes fatal damage if untreated. This is the first confirmed US case since the outbreak began to escalate in Central America and southern Mexico. Map: Spread of Screwworm Fly