Scientists warn Canada 'way behind the virus' as bird flu explodes among U.S. dairy cattle

While federal officials say there's still no sign of a dangerous form of bird flu in Canadian dairy cows, scientists warn limited surveillance means Canada might not be staying ahead of an explosive H5N1 outbreak among dairy cattle south of the border.

So far, dozens of herds across various U.S. states have been infected with this form of influenza A. While it appears to cause milder infections in cows, H5N1 has also been linked to stunning death rates of 50 per cent or more in other species, including various birds, cats and even humans, though more data and research is needed to fully understand the risks.

"I think we're way behind the virus," warned Matthew Miller, an immunologist and vaccine developer with McMaster University, who's among the Canadians working on H5N1 research.

Without a "robust national surveillance program, there's no way to know if there are infections here or not."

The Canadian Food Inspection Agency (CFIA) told CBC News on Monday it has not detected this form of bird flu yet in dairy cattle — or any other livestock — in Canada. (In birds, however, the disease is already widespread across the country, impacting an estimated 11 million farmed birds to date.)

The disease is federally reportable in any species, cattle included, the CFIA said. The agency requires dairy producers to monitor for signs of infection, follow biosecurity measures, and contact their local CFIA office if there is a "high degree of suspicion" of the disease.

It appears that cross-country trade is still allowed. Asked whether dairy cattle can currently be transported between the U.S. and Canada, the CFIA said the World Organisation of Animal Health "does not recommend restrictions on the movement of healthy cattle and their products at this time."

As well, following a U.S. federal order last Wednesday requiring H5N1 testing for many dairy cattle moving between states, "Canada will also require testing for [avian flu] on imported lactating dairy cattle from the U.S.," the CFIA said. 

When asked about testing milk samples, the agency said if H5N1 is detected in Canadian cattle, it will help provide testing support.

(The agency was more clear in an earlier statement on social media, saying it is "not currently testing raw or pasteurized milk," adding that the virus isn't a food safety concern.) 

Multiple Canadian scientists, however, stress that widespread testing and surveillance efforts should already be underway rather than set to ramp up after a first detection.

Canada should "absolutely be doing active surveillance for H5N1 in cattle," other animals and humans who are in close contact with them, said Dr. Isaac Bogoch, an infectious diseases expert with the University Health Network in Toronto, in correspondence with CBC News.

He said those efforts could include a range of approaches such as wastewater surveillance, blood sample studies and nasal swabs.

The goal should be going "all-in on prevention," Miller said, adding "pandemics always have the highest risk of happening when we have a virus in animals that humans are heavily exposed to."