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.

Federal health officials say a dairy worker in Nevada has been infected with a new type of bird flu that’s different from the version that has been spreading in U.S. herds since last year.