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, is different from a previous variant called B3.13 which had infected at least 40 dairy workers in the U.S. to date.

Until last week, all bird flu in dairy herds had been identified as the B3.13 variant, which was believed to have come from wild birds in late 2023 or early 2024. The USDA confirmed the virus's existence in the Nevada dairy cattle through milk sampling, the agency said.