Dairy cows in Nevada have been infected with a new strain of bird flu, marking the second strain detected in herds since March.

State officials say the highly pathogenic avian influenza – more commonly known as bird flu – is widespread in much of the state.

The finding indicates that the virus, known as H5N1, has spilled from birds into cows at least twice — leading to these two sets of infections — and that it could continue to do so. It also suggests that the virus may pose a persistent risk to cows and to the people who work closely with them.