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.

A version of the H5N1 virus that has killed one person and severely sickened another has been detected in milk samples collected from Nevada dairy herds.

Cows in Nevada have been infected with a strain of H5N1 bird flu different from the strain detected in all other herds to this point in the ongoing dairy outbreak. It's the same strain that killed a Louisiana resident in early January and sent a Canadian teenager to intensive care in early November.