A dairy worker in Nevada has reportedly been infected by the killer variant of H5N1 bird flu; analysis shows changes in new strain that makes it more lethal in mammals.

Nevada just confirmed its first human case of avian flu from infected cattle. Nevada’s first case was found in Churchill County, the Central Nevada Health District announced on Monday.

The newer strain had been seen before in more than a dozen people exposed to poultry, but this is the first time an infection was traced to a cow. The Nevada dairy worker was exposed at a farm in Churchill County, in the west central part of the state, state health officials said.