New H5N9 Bird Flu Strain Detected on California Duck Farm

The first U.S. case of H5N9 bird flu has been identified in Merced County, raising concerns about virus evolution but posing no immediate heightened risk to humans.

A new H5N9 strain of bird flu was detected on a commercial duck farm in Merced County, California, marking the first confirmed case in U.S. poultry.
The H5N9 strain is a reassortment of the widely known H5N1 and another low-pathogenic bird flu virus, but experts say it is not currently a greater threat to human health than existing strains.
All 119,000 ducks at the affected farm were euthanized in December 2024, and there have been no reports of the virus spreading to other farms or wild birds so far.
The Trump administration's pause on public health communications and withdrawal from the World Health Organization has raised concerns about delays in sharing critical disease outbreak information.
Researchers emphasize the importance of monitoring genetic changes in bird flu viruses, as reassortments like H5N9 highlight the potential for new strains to emerge.