Following the detection of HPAI H5N1 in dairy cattle in the United States, the USDA Wildlife Services National Wildlife Disease Program began conducting avian influenza surveillance in wildlife species captured on or around infected dairy and poultry facilities in April 2024. The goals of the program were to: 1) examine transmission dynamics between domestic animals and wildlife, 2) assess changes in the virus over time, 3) provide reports to producers about HPAI presence in wildlife on or near their facilities, and 4) compare apparent prevalence and virus strains detected on farms to those detected as part of routine wild bird surveillance efforts across the U.S. As of March 2025, USDA Wildlife Services has collected over 8,900 samples from at least 161 wild bird and mammal species from 59 affected premises across 16 states. Of the samples tested, 400 (4.5%) have tested positive for HPAI H5 via rRT-PCR, including novel detections in at least 11 passerine and 6 mammalian species, such as song sparrows, house mice, and black rats. Although prevalence and the diversity of infected species varied across premises, viral loads among peridomestic wildlife were generally low. Genetic analyses suggest that HPAI is moving from domestic animals to wildlife, but the “cattle strain” of HPAI does not appear to be sustained in the greater wildlife population. Critical to the success of these efforts has been long-established and positive relationships of USDA Wildlife Services personnel with producers, and continued surveillance of peridomestic wildlife will likely play an important role in identifying ways to mitigate transmission risks to domestic animals and people.

KRISTA E. DILIONE, U.S. Department of Agriculture, National Wildlife Disease Program, Fort Collins, CO JOURDAN RINGENBERG, U.S. Department of Agriculture, National Wildlife Disease Program, Fort Collins, CO MICHAEL MILLESON, U.S. Department of Agriculture, National Wildlife Disease Program, Gainesville, FL SCOTT STOPAK, U.S. Department of Agriculture, National Wildlife Disease Program, Boise, ID SARAH N. BEVINS, U.S. Department of Agriculture, National Wildlife Disease Program, Fort Collins, CO JULIANNA B. LENOCH, U.S. Department of Agriculture, National Wildlife Disease Program, Fort Collins, CO

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