Above 10 New World screwworm infestation cases in the United States during 2026

rationale:

This assessment estimates the probabilities of human New World screwworm (NWS) cases in the United States during 2026. The most critical factor for these thresholds is that the resolution criteria strictly apply to human cases only; the widely reported animal and livestock detections in Texas and New Mexico do not count toward this total 2 sources.

As of mid-June 2026, there are zero reported human cases of NWS in the U.S. cdc.gov. Historically, U.S. human NWS cases are exceedingly rare. The only confirmed human case in the last 50 years was a single travel-associated case in Maryland in August 2025, involving a traveler returning from El Salvador cdc.gov. Furthermore, historical outbreaks in animal populations do not easily translate to human transmission; for example, the 2016–2017 Florida Keys NWS outbreak caused over 130 animal cases but zero human cases avmajournals.avma.org.

Despite this very low historical baseline, the risk of at least one human case occurring in 2026 ("Above 0" at 39%) is elevated due to two primary pathways:

1. Imported cases: The ongoing, massive regional outbreak in Mexico and Central America involves over 185,000 animal cases and more than 2,100 human cases cdc.gov. Heightened surveillance and the sheer scale of the regional reservoir make the detection of imported travel-associated cases plausible.
2. Locally acquired spillover: The ongoing domestic animal outbreak in Texas and New Mexico raises the risk of sporadic local transmission. Human NWS infestations primarily pose a risk to individuals with untreated wounds in areas where flies are present, such as outdoor workers or unhoused populations .

However, U.S. health and agricultural agencies possess robust response capacities that severely limit the potential for a large cluster of human cases. The CDC activated a Level 3 response in early June, and the USDA is aggressively employing containment measures, including quarantines, movement controls, and expanding sterile-fly releases 2 sources. These interventions make sustained local human transmission highly improbable.

Consequently, the conditional distribution of cases heavily favors singletons or isolated incidents. The probabilities reflect a steep drop-off at higher thresholds. Exceeding 5 cases (6%) or 10 cases (3%) would require an unprecedented breakdown in outbreak control and sustained human spillover. We project that aggressive sterile-fly eradication and rapid public health responses will successfully confine the true count to zero or a very small number of isolated, predominantly travel-associated cases.