Since the flesh-eating screwworm fly reinvaded Mexico in 2024, human cases of the voracious parasite have been mounting. According to a July surveillance report from Mexico's Ministry of Health, there have been over 500 human cases in 2025 and 2026. A study this week in the journal Emerging Infectious Diseases analyzed the information on over 200 confirmed cases reported between April 2025 and March 2026 and found that the infestation pace is increasing.
Among the 200 confirmed cases in the study, six deaths were reported. At least one of the deaths was directly caused by the fly's maggots, researchers in Mexico reported in the study.
The New World screwworm (NWS) fly was once endemic in Mexico—as well as the US. The flies lay hundreds of eggs in the wounds, inflamed tissue, mucous membranes, and orifices of warm-blooded creatures. The resulting maggots hatch within a day and begin ravenously feasting on the living flesh of their victims. While the fly's maggots generate ghastly, life-threatening wounds in a variety of warm-blooded species, including humans, they're particularly devastating to livestock.
