A second subtype of H5 bird flu, known as D1.1, was detected in dairy cattle and infected one worker in the US state of Nevada. On February 10, 2025, the US Centers for Disease Control and Prevention released data showing the new D1.

The variant of bird flu that killed a Louisiana resident has now been found in dairy cows. Until now, the human cases of bird flu traced to cattle have been mild, mostly eye infections. But the U.S. Department of Agriculture confirmed that a strain previously found only in wild birds has turned up in dairy herds in Nevada ‒ raising concerns that future human infections could be more serious.