The newly reported H5N9 strain was found Monday at a duck farm in Merced County, California, according to the World Organization for Animal Health. The Paris-based organization that studies animal diseases said it's the first verified U.S. case of H5N9 in poultry. The organization said the more common strain H5N1 was also found.

As the bird flu continues to spread across the country, there's new evidence it's mutating beyond chickens and cows.

The patient had mild illness, and there is no evidence that the virus has spread to anyone else. View on euronews