H5N1 bird flu is branching out. New data from the Centers for Disease Control and Prevention indicates that a second type of H5N1 has likely spread from dairy cows to humans.

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 newer variant of avian influenza that recently infected dairy cattle in Nevada has a genetic change that’s thought to help the virus copy itself in mammals — including humans — more easily, according to a new technical brief from the US Department of Agriculture’s Animal and Plant Health Inspection Service.

While the H5N1 bird flu keep spreading, the first reported H5N9 outbreak in the United States has been identified on a duck farm in California.

The first outbreak of H5N9 bird flu in poultry has been reported in California on a duck farm leading to the culling of nearly 119,000 birds and concerns.

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.