H5N1 Bird Flu Spreads Across US Dairy Herds with 70 Human Cases Confirmed Nationwide This Year

This is Bird Flu Bulletin: Daily H5N1 Update for Wednesday, September 17th, 2025. Top Stories First, the United States continues to lead in confirmed H5N1 human cases, with at least 70 known infections since January, according to the CDC. The largest jump remains in California, now reporting 38 cases, mainly linked to exposure in dairy herds. Louisiana’s first H5-related death in the U.S. is prompting renewed calls for increased biosecurity in agricultural settings. Second, the Food and Agriculture Organization reports that 249 new animal H5 avian influenza outbreaks have occurred globally in the last month. The United States accounted for six new H5N1 events, bringing the U.S. animal outbreak total to over 3,500 for this wave. Europe is also seeing high activity, with France, Belgium, Norway, and the United Kingdom all reporting ongoing clusters in poultry and wild birds. Third, the joint FAO and World Health Organization assessment confirms there is still no evidence of sustained human-to-human H5N1 transmission, despite two new global human infection events reported in the past 24 hours. The vast majority of confirmed human cases continue to involve direct contact with either sick birds or cattle. There have been three known spillover events from birds into dairy cattle in the United States, with ongoing monitoring of animal-to-human infection risk. Case Numbers Update Compared to yesterday, there have been no new confirmed human H5N1 infections reported in the United States, with the CDC holding the cumulative number at 70. Globally, the Food and Agriculture Organization has logged two new human cases in the past day, both associated with direct animal contact. Animal outbreak numbers rose in multiple regions, particularly in North America and Western Europe. Latest Guidance The CDC has reiterated that the public health risk from H5N1 remains low for most people. However, they renew guidance for anyone working in close contact with poultry, wild birds, or dairy cattle. Use of personal protective equipment and strict farm hygiene protocols is strongly recommended. Health departments are also advising anyone with flu-like symptoms following animal exposure to seek testing promptly. The World Health Organization is continuing to urge countries to strengthen animal disease surveillance and reporting. Expert Interview Today we hear from Dr. Emily Garcia, infectious disease epidemiologist at the University of Washington: “While we have not seen sustained person-to-person H5N1 spread, the virus’s ability to cross from birds to cattle and then to humans warrants continued vigilance. Enhanced biosecurity in agricultural operations and rapid response to outbreaks are our best tools to protect both animal and human health.” Looking Ahead Tomorrow, we expect updates from the World Health Organization’s technical group, which is reviewing new sequence data from recent H5N1 outbreaks in cattle. The Centers for Disease Control and the USDA are This content was created in partnership and with the help of Artificial Intelligence AI.