Recent research by federal scientists warns of a “potentially devastating pandemic” if the virus ravaging poultry flocks eventually mutates and spreads efficiently between humans. An increase in avian flu infections in mammals has put Canadian wildlife and public health experts on high alert.
Human cases of avian influenza are extremely uncommon; there have been fewer than a dozen confirmed H5N1 cases globally since 2020, and there have been no instances of transmission between humans. The evolution of the highly pathogenic avian influenza H5N1 should be closely monitored, say experts, by public health agencies.
Dr. Samira Mubareka, an infectious disease specialist and clinician scientist at Sunnybrook Research Institute and the University of Toronto, stated, “There are enough red flags that we must prepare.”
In 1996, H5N1 was identified for the first time, but a new strain of the virus emerged in 2020. It was first detected in North America in late 2021 and has since decimated flocks of both wild and domesticated birds, resulting in the fatalities of millions of poultry in Canada due to infection or culls to prevent its spread.
Although cases in mammals are to be anticipated during an outbreak of bird flu, Mubareka stated that the variety of infected species has captured the attention of scientists.
“If the virus spreads to new species, it will always have the chance to mutate and adapt,” she explained. Therefore, this is an unprecedented level of H5N1 viral activity.
Since the beginning of last year, hundreds of confirmed cases of rabies in feral skunks, foxes, mink, and other mammals have been documented in Canada. This month, three outbreaks have been confirmed at poultry operations east of Montreal, and a fourth at a farm west of London, Ontario. Farmers are preparing for a potential influx of cases as migratory birds return this spring.
Public health agencies in Canada, the United States, and Europe concur that the risk to human health remains low, with cases almost always confined to direct contact with infected animals or contaminated environments, such as a chicken coop. There is no risk associated with eating poultry that has been adequately cooked.
However, scientists are carefully investigating the virus.
In a paper published last month, Canadian Food Inspection Agency scientists based in Winnipeg, where Canadian cases of H5N1 are confirmed and genetically sequenced, examined cases in forty different species of wild mammals. The researchers discovered that the virus had endured “critical mutations,” but the agency stated that the likelihood of human transmission remains minimal.
“The spillover of these viruses from wild birds to mammals could cause a potentially devastating pandemic if the H5N1 viruses mutate into forms that can spread efficiently among mammalian species,” according to a paper published in the peer-reviewed journal Emerging Microbes & Infections.
The critical mutations discovered by researchers involved a portion of the virus that aided it in replicating itself, adding to similar findings reported worldwide. In 17% of the cases, the scientists discovered mutations that gave the virus improved capabilities to replicate in humans.
The researchers noted, however, that the virus had not developed a distinct preference for attaching to receptors in a person’s nose, mouth, and throat – the target of influenza viruses and the key to human infection.
Multiple surveillance networks monitor and trace influenza viruses, as stated by the Public Health Agency of Canada, which takes the situation “very seriously.” In addition to the lessons learned from the COVID-19 pandemic, the government has reportedly developed H5N1-specific protocols for all government departments.
Professor and interim dean of the Ontario Veterinary College, Shayan Sharif, is most concerned about the possibility that the virus will evolve to become more dangerous to humans and acquire the ability to spread from person to person.
“I do not believe that this virus will spread,” he said. “I hope that I’m wrong.”
The U.S. Centers for Disease Control and Prevention recently produced a candidate vaccine virus for H5N1 that could, if necessary, be used to produce a vaccine for humans.
Canada, like the United States, has been reluctant to launch an H5N1 vaccine campaign for wildlife, but Sharif believes the government should consider doing so.
The 27 member states of the European Union have agreed to implement an avian flu vaccine strategy, with Mexico, Egypt, and China joining the list of countries immunising chickens against H5N1.
Sharif, an expert in avian influenza immunology in chickens, stated that targeted vaccination could help prevent poultry losses and reduce the spread of the virus, but it has also proven controversial due to import trade bans on vaccinated poultry out of concern that the birds may unwittingly introduce the virus.
A veterinary specialist with the CFIA, Marc Betrand, stated that Canada is not prepared to implement a vaccine strategy. Vaccines for H5N1 in chickens are “not that effective,” he said, and could wind up causing the virus to mutate further.
The Canadian Food Inspection Agency (CFIA), which leads the federal response to H5N1 in farmed birds, has stated that routine cleansing and isolating new birds are essential for preventing outbreaks.
According to Catherine Soos, a wildlife disease expert and research scientist with Environment Canada, avian flu has also affected wild bird populations in a “completely unprecedented” manner.
The federal agency is responsible for monitoring migratory animals and endangered species. Soos stated that the agency will keep a close watch on returning migratory bird populations this spring, as they may carry new strains of the virus.
It is also observing how certain migratory bird species severely impacted by H5N1 recover this year. Soos estimated that approximately 1,600 breeding female Common eiders were discovered deceased along the Gulf of St. Lawrence last year, representing five to fifteen percent of the population.
She stated, “We must definitely monitor these populations.”
