The New World Screwworm in the United States: A Narrative Review Anchored to the 2025 Travel-Associated Human Case.

The New World screwworm (Cochliomyia hominivorax) is an obligate parasitic fly whose larvae invade and consume living tissue, causing myiasis with severe consequences for human health, animal welfare, and agricultural productivity. Although eradicated from the United States in the 1960s through the sterile insect technique (SIT) and contained thereafter by a Panama-based biological barrier, the parasite remains endemic in parts of South America and the Caribbean. Endemicity in these regions sustains the risk of reintroduction into screwworm-free areas. A recent travel-associated case of human screwworm in the United States highlights this ongoing threat, though no evidence of local transmission has been detected. While the public health risk in the United States remains low, the agricultural stakes are substantial: screwworm outbreaks can cause significant morbidity and mortality in livestock, necessitating costly interventions and resulting in considerable economic losses if detection and control are delayed. This review synthesizes the biology and pathogenesis of C. hominivorax, the historical trajectory of eradication efforts, details of the most recent U.S. case, the ongoing risks to public health and agriculture, and current and emerging prevention strategies. We emphasize that future resilience will depend on embedding surveillance and control in a One Health framework, maintaining redundant SIT capacity, integrating climate-informed risk models, and fostering international collaboration. The recent U.S. case should be interpreted as a sentinel event that reaffirms the fragility of eradication gains and the need for sustained vigilance.