A branch of the H5N1 bird flu family tree that hadn't previously been seen in cattle has now been detected in dairy cows.

A second strain of bird flu has been detected in U.S. dairy cattle, marking the first confirmed infections of this particular virus in cows, the U.S. Department of Agriculture said.

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.