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.

The newer strain had been seen before in more than a dozen people exposed to poultry, but this is the first time an infection was traced to a cow.

A dairy worker in Nevada has been confirmed to be infected by a new bird flu strain found to be spreading among cows in the state last week. That strain of the H5N1 bird flu virus, called D1.1 by scientists,