New evidence shows that bird flu, or avian influenza, is mutating beyond chickens and cows. A Nevada dairy worker tested positive for the new variant of the disease.

This version of the virus is circulating broadly in wild birds and is different from the virus that has been causing dairy cow outbreaks since early 2024, the CDC said.

Federal health officials say a dairy worker in Nevada has been infected with a new type of bird flu that’s different from the version that has been spreading in U.S. herds since last year.