New World screwworm: a re-emerging parasitic threat

Purpose of review New World screwworm (NWS) is an emerging parasitic threat in Central America and Mexico, which is spreading northward into the southern United States. Here we highlight the changing epidemiology, lifecycle of the NWS fly, clinical presentation, identification, treatment, and potential complications of NWS myiasis. Recent findings Despite decades of successfully containing NWS flies south of the Darien Gap in southern Panama, NWS flies reemerged in the Central America region in 2023 and have continued to spread northward ever since. On 3 June 2026, United States Department of Agriculture (USDA) confirmed the identification of an NWS infestation in a young calf in southern Texas. In addition to describing the current epidemiology of the NWS outbreak, we present information about clinical presentation and management of NWS myiasis in patients and include representative cases of patients who experienced NWS myiasis. Summary This review provides important epidemiologic and clinical updates to an emerging parasitic threat so clinicians can understand the risks and clinical management for patients with suspected NWS myiasis.