A strain of bird flu spreading among dairy cows in Nevada has infected a dairy worker in the state, the Centers for Disease Control and Prevention said Monday.

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.

Amid rising respiratory illnesses, a CDC report reveals undetected bird flu cases in US veterinarians. The spread, shown through antibody tests, indicates infections occurring beyond known zones. Experimental confirmation of H5N1 transmission through cow milk prompts officials to urge all states to join the national milk testing program.