Resurgence of the New World Screwworm Fly Poses New Human Health Risk

The New World screwworm fly (*Cochliomyia hominivorax*) was declared eradicated in Mexico in 2003 after a decades-long campaign that pushed the infestation barrier to Panama. Since late 2024, livestock cases have reappeared in Mexico, and the fly has moved northward. In June 2024 the species was confirmed to have re-entered the United States, marking the first official return in decades.

Gizmodo

Researchers analyzing Mexican Ministry of Health surveillance data identified 204 human myiasis cases between April 2025 and March 2026, most affecting men’s lower limbs. Six individuals died after infestation, and one death was directly attributed to the screwworm. A later Ministry report notes that more than 500 human cases have been detected in Mexico since the fly’s reemergence. In the United States, 45 cases have been recorded in Texas and New Mexico as of August 9, but the Centers for Disease Control and Prevention reports no human infections to date and characterizes overall public risk as very low.

Gizmodo

The study authors stress that coordinated action across human health, animal health, wildlife, and agricultural sectors is essential for prevention and control. Mexican officials recommend proactive surveillance, diagnostic preparedness, animal-movement restrictions, and fly-suppression activities at the leading edge of the northward spread. U.S. authorities have responded by deploying sterile-male fly releases around detected sites, a core tactic of earlier eradication programs.

Gizmodo

Both countries acknowledge that the screwworm’s resurgence could expand if containment fails. Continued monitoring of livestock outbreaks, rapid diagnostic capacity, and sustained sterile-fly releases are identified as critical to limiting further human exposure. The situation remains under close observation as the fly continues to re-establish footholds across the border region.

Gizmodo