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, sci‐ entists warn limited sur‐ veillance means Canada might not be staying ahead of an explosive H5N1 out‐ break 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 in‐ fections in cows, H5N1 has also been linked to stunning death rates of 50 per cent or more in other species, includ‐ ing 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 Mc‐ Master University, who's among the Canadians work‐ ing 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 In‐ spection 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 dis‐ ease is already wide‐ spreadacrossthe country, im‐ pacting an estimated 11 mil‐ lion farmed birds to date.)

The disease is federally re‐ portable in any species, cattle included, the CFIA said. The agency requires dairy pro‐ ducers to monitor for signs of infection, follow biosecu‐ rity measures, and contact their local CFIA office if there is a "high degree of suspi‐ cion" of the disease.

It appears that crosscountry trade is still allowed. Asked whether dairy cattle can currently be transported between the U.S. and Cana‐ da, the CFIA said the World Organisation of Animal Health "does not recommend restrictions on the move‐ ment 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 be‐ tween states, "Canada will al‐ so 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 scien‐ tists, however, stress that widespread testing and sur‐ veillance efforts should al‐ ready be underway rather than set to ramp up after a first detection.

Canada needs 'active surveillance'

Canada should "absolutely be doing active surveillance for H5N1 in cattle," other ani‐ mals and humans who are in close contact with them, said Dr. Isaac Bogoch, an infec‐ tious diseases expert with the University Health Net‐ work in Toronto, in corre‐ spondence with CBC News.

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

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

Given H5N1's unprece‐ dented leap into cattle, fol‐ lowed by explosive cow-tocow spread across the U.S. in mere weeks, the potential for human-to-human transmis‐ sion seems more likely as the virus adapts to more mam‐ mals, he warned.

"If we see more human in‐ fections, cat's out of the bag, it's way too late," Miller said. "We need to be sparing no amount of effort, and no amount of expense, in doing absolutely everything to pre‐ vent even those initial infec‐ tions in humans - because the stakes are just too high."

The U.S. has reported one human infection linked to the cattle outbreaks so far, in an individual whose only symp‐ tom was eye inflammation. However, some scientists have warned there are likely more that aren't being de‐ tected, amid growing calls for mass testing on farms.

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"Since the issue in the [U.S.] seems to be bigger

than we thought and was brewing before it was recog‐ nized, and since we have a plausible route for exposure here, we should be proac‐ tive," said Dr. Scott Weese, a professor at the Ontario Vet‐ erinary College and director of the University of Guelph's Centre for Public Health and Zoonoses.

At a minimum, he added, that would involve milk sur‐ veillance. It may not be par‐ ticularly sensitive - the milk supply is diluted because it comes from so many farms, Weese said.

"But if there are positives, we know we have it and then need to look more aggres‐ sively at the farm level."

Despite sick cows being pulled from production lines, U.S. Food and Drug Adminis‐ tration officials said its recent nationwide survey of milk sold on store shelves found viral remnants of H5N1 in one in five samples. (More re‐ assuringly, federal tests sug‐ gest pasteurization - a heat‐ ing process meant to neutral‐ ize harmful pathogens - does ensure milk is safe to drink.)

On Monday, the U.S. De‐ partment of Agriculture (US‐ DA) also announced there will be testing of ground beef in states with bird flu out‐ breaks, and recently warned the virus may be passing back and forth between cat‐ tle and poultry farms.

Outbreak officially spread to 34 herds, 9 states

The first known cattle in‐ fected with H5N1 were re‐ ported in late March. Since then, at least 34 herds across nine U.S. states have been impacted, and scientists sus‐ pect the outbreak is already far bigger than official figures suggest.

Newly released research from the U.S. Centers for Dis‐ ease Control and Prevention also showed profound im‐ pacts on farm cats - with a death rate of around 50 per cent among those fed raw milk products from infected cows.

The study raises "new concerns regarding the po‐ tential for virus spread within mammal populations," the team continued.

WATCH | Quebec poultry industry suffers avian flu outbreaks:

On Monday, other U.S. re‐ searchers shared a preprint research not yet formally published or peer-reviewed outlining efforts to monitor influenza A at dozens of wastewater sites this spring.

The team tested samples from three plants where spring rises in influenza A were observed, and found a marker for the H5 gene at all three facilities. Those plants were also located in an un‐ named state with confirmed H5N1 outbreaks among dairy cattle, and two of the facili‐ ties discharged animal waste and milk byproducts into sewers, the researchers noted.

It all paints a picture of a fast-spreading outbreak that's impacting new species, appearing in new areas, and is likely past the point of con‐ taining, several outside scien‐ tists agreed.

Funding, support for testing needed

Here in Canada, funding and support for veterinarians and farmers to test needs to be clear, stressed Weese.

"If farmers have to pay for sampling and testing, and don't know what will happen if there's a positive, and have no direct personal gain from it, why would they do it vol‐ untarily?" he questioned. "We need a clear program that supports good testing and supports farms."

Toronto-based infectious diseases specialist Dr. Allison McGeer, from Sinai Health System, said she's "personal‐ ly hoping we are not going to get caught off guard" here in Canada.

What's reassuring, McGeer added, is that Cana‐ da does have robust human testing in place to catch se‐ vere flu infections. Typically, she says, Canadian hospitals use combined viral testing for COVID, influenza and RSV - which can pick up a certain protein that is stable across all strains of influenza A.

If a human infection of avian flu showed up in a hos‐ pital, the test would label it along the lines of "influenza A, subtype not detected," she explained. And, if the patient had also been in contact with poultry or wildlife, that com‐ bination of factors could trigger extra lab work to pin‐ point the specific type of in‐ fluenza - including H5N1.

But that's only if someone is sick enough to visit a healthcare facility.

"It's not a perfect system," McGeer acknowledged, "but it's [a sensitive system] for detecting severe disease from H5N1."