‘Potentially devastating’: Bird flu cases in mammals put scientists on alert

The rise in the number of mammals infected with bird flu has put Canada’s wildlife and public health experts on alert, as recent research by federal scientists warns that if the virus ravaging poultry flocks eventually mutates to be effective in humans spread, triggering a “potentially devastating pandemic”.

Cases of bird flu are very rare in humans — fewer than a dozen confirmed cases of H5N1 have been confirmed globally since 2020 — and there has been no human-to-human transmission. But experts say public health agencies are right to keep a close eye on the evolution of highly pathogenic bird flu H5N1.

“There are enough red flags that we need to be prepared,” said Dr. Samira Mubareka, an infectious disease specialist and clinician-scientist at the Sunnybrook Institute and the University of Toronto.

H5N1 was first discovered in 1996, but in 2020 a new virus emerged. It was first detected in North America in late 2021, and since then a massive decimation of wild and domestic birds has resulted in millions of poultry across Canada dying from the infection or culled to prevent its spread.

While mammalian cases are expected during bird flu outbreaks, Mubareka said part of what caught scientists’ attention was the range of infected species.

“If a virus spreads into a new species, there’s always an opportunity for it to mutate and adapt further,” she said. “So this is really an unprecedented level of viral activity for an H5N1 virus.”

Last week, Canada reported its first case in a pet dog, adding to the hundreds of confirmed cases in wild skunks, foxes, minks and other mammals since early last year. With three outbreaks this month at a poultry farm east of Montreal and a fourth at a farm west of London, Ont., farmers are bracing for a possible wave of cases as migratory birds return this spring.

Public health agencies in Canada, the United States and Europe agree that the risk to human health from the virus remains low, and cases are almost always limited to direct contact with infected birds or contaminated environments, such as poultry houses. There is no risk in consuming thoroughly cooked poultry products.

However, scientists are studying the virus closely.

In a paper published last month, Canadian Food Inspection Agency scientists studied cases in 40 different wild mammals in a laboratory in Winnipeg, where the H5N1 cases in Canada were confirmed and gene sequencing. The researchers found some “key mutations” in the virus, although the agency said the likelihood of human transmission remains low.

“Transmission of H5N1 viruses from wild birds to mammals could lead to potentially devastating pandemics if H5N1 viruses mutate into forms that can transmit efficiently in mammalian species,” the paper, published in the peer-reviewed journal Emerging Microbes & Infections The paper writes.

The key mutation the researchers identified involves a part of the virus that helps the virus replicate itself, adding to similar findings reported around the world. In 17 percent of cases, the scientists found changes that gave the virus a better advantage in replicating in humans.

But there are encouraging signs, the researchers write, that the virus has not developed a strong preference for targeting receptors in a person’s nose, mouth and throat — the target of influenza viruses and the key to human infection.

The Public Health Agency of Canada says it takes the situation “taken very seriously” and is monitoring and tracking the flu virus through multiple surveillance networks. Combined with the lessons learned from the COVID-19 pandemic, it said it had been able to develop a plan for H5N1 across government departments.

Shayan Sharif, a professor and acting dean of the Ontario College of Veterinary Medicine, said his biggest concern is that the virus could change so that it becomes more dangerous to humans and acquires the ability to spread from person to person.

“I don’t think this virus is going anywhere,” he said. “I hope I’m wrong.”

The U.S. Centers for Disease Control said it recently produced a candidate H5N1 vaccine virus that could be used to produce a vaccine for humans if needed.

As for poultry, Canada and the US have so far been reluctant to launch H5N1 vaccination campaigns for birds, but Sharif said the government should consider taking this step.

The 27 member states of the European Union have agreed to implement a bird flu vaccine strategy, with Mexico, Egypt and China adding to the list of countries vaccinating chickens against H5N1.

Sharif, who specializes in bird flu immunology in chickens, said targeted vaccinations could help prevent poultry losses and reduce the spread of the virus, but a trade ban on the import of vaccinated poultry due to concerns that birds could inadvertently introduce the vaccine, said This also proved controversial. Virus.

CFIA veterinary expert Marc Betrand said Canada is not yet ready to roll out a vaccine strategy. He said the H5N1 chicken vaccine was “not very efficient” and could end up triggering more mutations in the virus.

The CFIA, which is leading the federal response to H5N1 in farmed birds, says measures such as routine cleaning and quarantining new birds are key to preventing outbreaks.

Bird flu has also hit wild bird populations in “unprecedented” ways, said Catherine Soos, a wildlife disease expert and Environment Canada research scientist.

Federal agencies are responsible for monitoring migratory birds and species at risk. This spring, Soos said, it will keep a close eye on migratory bird populations returning north, which could bring new versions of the virus with them.

It is also watching how certain wild birds hit hard by H5N1 bounce back this year. About 1,600 breeding female common eider ducks died last year along the Gulf of St. Lawrence coast, Soos said, accounting for an estimated 5% to 15% of the population.

“We absolutely want to monitor these populations,” she said.

—Jordan Olmsted, Canadian Press

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