A genetic mutation of the H5N1 bird flu virus — a mutation associated with increased infectiousness and disease severity — has been found in two cats, in what scientists say is another indication of the risks posed by the virus.

The ongoing bird flu outbreak has led to wild bird deaths, slaughtered livestock, and hazardous conditions for dairy industry workers.

Health officials urged pet owners not to let their felines roam outdoors or feed them raw food or raw milk — common ways avian influenza can be transmitted.