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. At least one of the deaths was directly caused by the fly’s maggots, researchers in Mexico reported in the study. While human NWS infections—called myiasis—are a small fraction of the overall cases, the infestations can be severe and horrifying. In 2025, the cases were being reported at a rate of about three per week.