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.

Scientists are sounding alarms about a genetic mutation that was recently identified in four dairy cow herds, nearly one year after H5N1 bird flu was first reported in Texas dairy cattle.

Health authorities say the threat of infection for people remained low even amid the spread of H5N1 virus among birds and cattle nationally.