A recent outbreak of the highly pathogenic H5N1 virus in the U.S. marks the first instance of avian flu infecting bovines. The outbreak is also believed to be the first occurrence of mammal-to-human transmission of the virus, as a dairy worker in Texas presumably contracted it after contact with cattle.

Since late March, avian flu outbreaks have been documented among dairy herds across eight U.S. states, prompting 17 states to impose restrictions on cattle imports from affected regions.

Although avian flu has been present in wild bird populations for years, there has been a recent surge in outbreaks among domestic poultry and other animals, including minks, seals, and sea otters, since 2022.

Canadian officials have been monitoring avian influenza on dairy farms since the initial case was reported in U.S. cows. The Canadian Food Inspection Agency (CFIA) assures no bovines in Canada have contracted the virus. While it has been detected in various bird and mammal species in Canada, including domestic dogs, human infections have not been confirmed.

In conversation with The Globe and Mail, CFIA senior director Martin Appelt states the U.S. outbreak is an evolving influenza virus likely introduced to cattle through wild birds and poultry. He reports there is no indication of a severe spread of fatal disease among cattle, with the infection rate estimated at approximately 10 per cent in impacted herds.

“Most of those animals appear to be recovering just fine with some supportive care, which really does not tick the boxes for a dramatic foreign animal disease that requires drastic measures to tackle,” said Appelt. “I think it would be unfair and very premature to fall into any sort of panic mode at this point.”

Further, the U.S. outbreak is of little concern to Canadian dairy consumers, as pasteurization effectively eliminates the virus.