A bird flu outbreak infecting dairy cows in the United States that has seeped into the country’s milk supply is under investigation amid growing questions about the risks to humans.
Colombia became the first country this week to restrict the import of beef and beef products from multiple U.S. states where some dairy cattle have tested positive for avian influenza as of April 15, according to the U.S. Department of Agriculture.
The U.S. Food and Drug Administration (FDA) announced on Tuesday that samples of pasteurized milk tested positive for remnants of the Highly Pathogenic Avian Influenza (HPAI) that has infected dairy cows.
In an update Thursday, the agency said about one in five retail samples tested positive for HPAI viral fragments, “with a greater proportion of positive results coming from milk in areas with infected herds.”
Despite that, FDA officials have allayed concerns about risks to consumers because of the pasteurization process, that kills harmful bacteria and viruses, as well as the diversion or destruction of milk from sick cows.
“To date, the retail milk studies have shown no results that would change our assessment that the commercial milk supply is safe,” the FDA said Thursday.
Canada has so far not detected the bird flu virus in dairy cattle or other livestock, but the Canadian Food Inspection Agency (CFIA) says it is monitoring the situation closely.
“We are working with the veterinary community, industry, public health authorities and the provinces and territories to coordinate a national response,” the CFIA said in a release last week.
Avian flu does not pose a food safety concern and the risk of transmission to humans remains low, the agency said.
The World Health Organization is also investigating the bird flu virus known as Type A H5N1 detected in milk and its potential role in transmission.
“Based on available information, WHO assesses the current overall public health risk posed by A(H5N1) to be low, and for those with exposure to infected birds or animals or contaminated environments, the risk of infection is considered low-to-moderate,” the global health body said in statement Friday.
What are the risks to humans?
Detecting bird flu in milk is “quite unusual” but not “very surprising” since the virus was already circulating among dairy cattle in the U.S, said Shayan Sharif, a professor at the Ontario Veterinary College at the University of Guelph.
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“Presence of the virus in milk means that the virus is being shed in milk, but the good thing is that pasteurization, by and large, should be able to kill the virus,” he said in an interview with Global News.
“It’s unlikely that in pasteurized milk you would have a live virus or a virus that can retain its infectivity,” Sharif added.
He said the risks would be “relatively higher” if the milk was not pasteurized.
As a general practice, the WHO strongly advises that people consume pasteurized, and not raw, milk.
Dairy cattle affected by the bird flu virus are showing decreased lactation, low appetite, and other symptoms, according to the FDA.
“H5N1 is a very severe virus, and it has different effects in different animals,” said Dr. Isaac Bogoch, an infectious disease specialist at the University of Toronto.
“The real concern here is that if you have more of this virus circulating in mammal populations, it has the opportunity to pick up mutations that might make it more easily transmitted between mammals,” Bogoch told Global News in an interview Friday. “And that would be a problem because this virus can be deadly and it has epidemic and pandemic potential.”
To date, no U.S. beef cattle have tested positive for bird flu, according to government officials.
Should other countries halt U.S. beef imports?
Colombia is the only country that has officially imposed restrictions on U.S. beef exports over the H5N1 outbreak, Joe Schuele, a spokesperson for the U.S. Meat Export Federation, told Reuters.
Sharif said the Colombian restrictions could primarily be a “precautionary measure.”
“I don’t really think that (Canada is) at that point yet because there’s really no evidence that beef cattle may also become infected,” he said.
Sharif also said that there is no evidence to suggest that beef can harbour bird flu and the virus can retain its infectivity in beef.
Even so, thoroughly cooking beef will kill the virus, the CFIA says.
The agency also advises handwashing and keeping meat products separate from other food products to avoid cross contamination.
At this time, the World Organization for Animal Health does not recommend imposing “unjustified trade restrictions” in response to the bird flu outbreak in U.S. cattle.
Canada already has restrictions in place on imports of poultry, poultry products and live birds from other countries affected by a bird flu outbreak.
“We will continue to closely monitor the evolving situation and will consider any additional measures, as necessary,” the CFIA says.
Avian flu can impact both the poultry industry and wildlife.
The virus is spread through contact with an infected bird or poultry products. Although rare, humans and non-avian species can also get infected.
In Canada, there have also been some sporadic bird flu cases detected in raccoons, striped skunks, red foxes, cats and dogs.
— With files from Reuters and The Associated Press