Four black rats in Riverside County, California, located east of Los Angeles, have tested positive for the H5N1 virus. The US Department of Agriculture confirmed on 19 February that this was the first known case of avian influenza in this species.

Health officials found the four rats over a three-day period, from January 29 to 31.

The virus has now been confirmed in other rodents such as mice and squirrels.

The Centers for Disease Control and Prevention said the risk of avian flu to the U.S. population remains low at this time.

In Canada, the risk to the population also remains low. But this week, the Public Health Agency of Canada (PHAC) announced that it has purchased 500,000 doses of bird flu vaccine for humans.

The vaccines were ordered as a "proactive measure" in case those doses need to be purchased, PHAC said.

In Canada, bird flu has been found sporadically in mammals such as raccoons, striped skunks, red foxes, cats and dogs. However, the Canadian Food Inspection Agency has reported no cases of avian flu in rats. | BGNES