U.S. senators urged USDA to advance a science-based HPAI vaccination strategy, citing the scale of the outbreak—more than 184 million birds and over 1,000 dairy herds affected since 2022—and warning that winter conditions could accelerate spread. Indiana continues to anchor U.S. activity, with 66 commercial poultry flocks lost in 2025, while Texas confirmed a commercial outbreak involving a 260,000-bird broiler flock. Viral spread beyond poultry persisted, with Wisconsin reporting an HPAI case in dairy cattle. New research added to human-health concerns, showing H5N1 can bind to mammary tissue across multiple species, including humans, reinforcing risks tied to raw dairy exposure. Abroad, Europe’s 2025 outbreak total has surpassed prior years, while Asia-Pacific countries reported additional commercial outbreaks.
U.S. Senators Press USDA to Advance Bird Flu Response
A bipartisan group of U.S. senators urged Agriculture Secretary Brooke Rollins in a December 11 letter to prioritize a science-based HPAI vaccination strategy, citing the scale of the outbreak—more than 184 million birds and over 1,000 dairy herds affected nationwide since 2022—and warning that winter conditions are likely to accelerate spread. They also acknowledged that poultry vaccination carries significant implications for exports and international trade—many trading partners restrict imports from countries that vaccinate poultry. Industry groups expressed support but emphasized that any vaccination strategy must preserve market access and trade continuity (Doughman, 2025).
HPAI Activity Across Upper Midwest, Indiana Still Most Affected
Avian influenza activity continued across multiple Midwestern states in early December, with Indiana remaining the most concentrated center nationwide. Since the last edition of this report on December 5, Indiana has reported 49,600 new infections across five farms in Elkhart and LaGrange counties (United States Department of Agriculture, 2024). Indiana has now lost 66 commercial poultry flocks in 2025, spanning ducks, turkeys, layers, broilers, and breeders (United States Department of Agriculture, 2024). Elsewhere, Minnesota confirmed HPAI on December 9 in a flock of 20,900 meat turkeys in Waseca County, its first commercial case since October 22 (Graber, 2025b). North Dakota also reported a December 9 outbreak involving 19,500 turkeys in Richland County, while South Dakota confirmed a December 5 case in Kingsbury County affecting 38,700 turkeys. According to APHIS, active HPAI control areas remain in seven states: Indiana, Minnesota, South Dakota, North Dakota, Iowa, Michigan, and North Carolina (Graber, 2025a).
APHIS Confirms HPAI in 260,000-Bird Commercial Broiler Flock in Texas
On December 15th, USDA APHIS confirmed that a commercial broiler flock of 260,000 birds in Shelby County, Texas, tested positive for avian influenza. The outbreak was initially reported by the Texas Animal Health Commission after significant mortality was observed, with samples testing positive on December 11 at a Texas A&M diagnostic laboratory. This marks Texas’s first commercial poultry HPAI detection of 2025; earlier detections this year were limited to backyard flocks. The last commercial outbreak in the state occurred in April 2024, when nearly 1.9 million laying hens were affected in Parmer County (Graber, 2025c).
Study Finds H5N1 Can Bind to Mammary Glands Across Multiple Species, Including Humans
New research from Iowa State University, George Mason University, and the U.S. Department of Agriculture shows that H5N1 avian influenza can infect mammary glands in a wide range of species, including pigs, sheep, goats, beef cattle, alpacas, and humans. The findings build on earlier concerns raised after high levels of the virus were detected in dairy cow udders and raw milk. Researchers identified shared cell receptors that allow the virus to attach to mammary tissue, pointing to potential exposure risks for farm workers and consumers of raw dairy products. The study adds to growing evidence that consumption of unpasteurized dairy may pose elevated risks during ongoing H5N1 circulation (Cramer, 2025).
Eight European Countries Report New HPAI Outbreaks in Commercial Poultry
Avian influenza continues to intensify across Europe, with eight countries confirming new H5N1 outbreaks on commercial poultry farms in early December, according to European Commission data. As of December 10, a total of 654 commercial poultry outbreaks had been recorded across 23 European countries in 2025, exceeding full-year totals from both 2023 and 2024. Germany remains the most affected country, followed by Poland, Hungary, France, Italy, and the Netherlands. France reported the highest number of recent outbreaks and has affected more than 1.3 million birds since October. Additional outbreaks were reported in Germany, Portugal, Poland, Italy, the Netherlands, Denmark, and Lithuania, displaying widespread transmission across northern and western Europe (Linden, 2025b).
Wisconsin Confirms First-Ever HPAI Detection in a Dairy Cattle Herd
Wisconsin officials confirmed the state’s first detection of highly pathogenic avian influenza in dairy cattle after routine milk testing identified H5 clade 2.3.4.4b in a Dodge County herd, with results confirmed by USDA laboratories on December 14–15 (Soucheray, 2025). The farm had previously tested negative multiple times and reported no recent cattle movement or signs of illness in the herd. State and federal officials said the detection does not pose a risk to consumers, emphasizing that pasteurization inactivates the virus and that milk from affected animals is diverted or destroyed. The herd has been quarantined, biosecurity measures have been reinforced, and farm workers are being monitored, marking Wisconsin’s first cattle case amid broader seasonal HPAI activity in poultry and wildlife nationwide (Conquest-Ware, 2025).
Asia-Pacific Outbreaks Continue: South Korea, Japan, Philippines
South Korea confirmed four additional H5N1 outbreaks in commercial poultry since early December, bringing the seasonal total to 10 outbreaks since mid-September and affecting nearly 663,000 birds across five provinces. Recent cases included the country’s first duck outbreak of the season, involving about 20,600 birds, and two laying-hen farms totaling nearly 59,000 birds. Japan also reported a new H5N1 outbreak in early December at a broiler farm in Tottori prefecture affecting roughly 75,500 birds, raising its season total to six. In the Philippines, two active H5N1 poultry outbreaks continued on the northern island of Luzon, involving chickens, ducks, and broiler breeders (Linden, 2025a).
Bird Flu Confirmed After Dozens of Vultures Found Dead at Ohio School
Ohio health officials confirmed bird flu after 72 vulture carcasses were found on the grounds of a Catholic school near Cincinnati, with at least two testing positive and the remaining birds presumed infected. The carcasses were discovered in late November at Saint Bernadette School in Pierce Township and remained on site for several days amid delays over responsibility for removal (Vigdor, 2025).
References
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Cramer, R. (2025, December 10). Researchers find mammary glands of people, sheep and other livestock could harbor bird flu. Iowa Public Radio. https://www.iowapublicradio.org/agriculture/2025-12-10/bird-flu-research-mammary-glands-people
Doughman, E. (2025, December 12). Senators to USDA: Time to prioritize HPAI poultry vaccine. WATTPoultry.com. https://www.wattagnet.com/poultry-meat/diseases-health/avian-influenza/news/15774048/senators-to-usda-time-to-prioritize-hpai-poultry-vaccine
Graber, R. (2025a, December 11). HPAI hits turkeys in North and South Dakota, ducks in Indiana. WATTPoultry.com. https://www.wattagnet.com/poultry-meat/diseases-health/avian-influenza/news/15773942/hpai-hits-turkeys-in-north-and-south-dakota-ducks-in-indiana
Graber, R. (2025b, December 12). Avian flu hits flock of 20,900 Minnesota turkeys. WATTPoultry.com. https://www.wattagnet.com/broilers-turkeys/turkey/news/15774068/avian-flu-hits-flock-of-20900-minnesota-turkeys
Graber, R. (2025c, December 17). HPAI-hit flock in Texas involved 260,000 broilers. WATTPoultry.com. https://www.wattagnet.com/poultry-meat/diseases-health/avian-influenza/news/15774365/hpaihit-flock-in-texas-involved-260000-broilers
Linden, J. (2025a, December 12). Season’s avian flu outbreak total in South Korean poultry rises to 10. WATTPoultry.com. https://www.wattagnet.com/poultry-meat/diseases-health/avian-influenza/news/15774047/seasons-avian-flu-outbreak-total-in-south-korean-poultry-rises-to-10
Linden, J. (2025b, December 16). 8 European states confirm new avian flu outbreaks on poultry farms. WATTPoultry.com. https://www.wattagnet.com/poultry-meat/diseases-health/avian-influenza/news/15774247/8-european-states-confirm-new-avian-flu-outbreaks-on-poultry-farms
Soucheray, S. (2025, December 15). Center for Infectious Disease Research and Policy. CIDRAP. https://www.cidrap.umn.edu/avian-influenza-bird-flu/wisconsin-detects-avian-flu-cattle-first-time
United States Department of Agriculture. (2024, June 20). HPAI Confirmations in Commercial and Backyard Flocks. Www.aphis.usda.gov. https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/commercial-backyard-flocks
Vigdor, N. (2025, December 9). Bird Flu Is Suspected After Vulture Carcasses Sat Rotting Outside Ohio School. The New York Times. https://www.nytimes.com/2025/12/09/us/dead-vultures-bird-flu-ohio.html