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.

Officials are urging pet owners not to feed their pets raw food or raw milk and to avoid letting them roam outside.