Highly pathogenic H5N9 avian influenza has been detected for the first time in US poultry since 2014, at a duck meat farm in California. The outbreak began in November 2024 and was confirmed by tests from the USDA National Veterinary Services Laboratory. State officials quarantined the affected farm and culled nearly 119,000 birds by December 2.
Dr. Angela Rasmussen of Canada’s Vaccine and Infectious Disease Organization noted that H5N9 detection suggests reassortment of H5N1 viruses with avian flu containing the N9 neuraminidase. She emphasized ducks are great hosts for such viruses, as they remain infectious while flying and eating. However, the risk to humans remains unclear but highlights the importance of preventing H5N1 spread in pigs due to their susceptibility to other flu issues.
The outbreak has affected 11 states, 26 counties, and over 3 million birds, including layer flocks, turkeys, and broilers across the Midwest and West. In California alone, 943 avian influenza H5N1 cases were confirmed, with 726 in dairy herds. APHIS is continuing to investigate and respond to these challenges.
Source: https://www.cidrap.umn.edu/avian-influenza-bird-flu/tests-identify-h5n9-avian-flu-california-duck-farm