The rise in the number of mammals infected with bird flu has alerted Canadian wildlife and public health experts, as recent research by federal scientists warns of a “potentially devastating pandemic” if the virus that plagues poultry farms eventually mutates to spread effectively among humans.
Bird flu cases are very rare in humans — fewer than a dozen H5N1 cases have been confirmed worldwide since 2020 — and there have been no cases of human-to-human transmission. But experts say public health agencies are right to keep a close eye on developments in the highly pathogenic H5N1 avian flu.
“There are enough red flags that we need to be prepared,” said Dr. Samira Mubareka, an infectious disease specialist and clinician scientist at Sunnybrook Research Institute and the University of Toronto.
The H5N1 virus was first identified in 1996, but a new type of virus emerged in 2020. First detected in North America in late 2021, it has since wiped out flocks of wild birds and domestic animals, resulting in the death of millions of poultry in Canada, either from infection or from systematic culling to prevent its spread.
Although mammalian cases are to be expected during an outbreak of bird flu, Mubareka says what has caught scientists’ attention is partly the range of species infected.
“If the virus spreads to new species, it always has the possibility of mutating and adapting even further,” she explains. This is therefore an unprecedented level of viral activity for H5N1.
The first case in Canada was reported last week in a dog, which had chewed on a wild goose. This case joins hundreds of others confirmed in wild skunks, foxes, mink and other mammals since early last year.
Earlier this month, three outbreaks were confirmed in poultry farms east of Montreal and a fourth on a farm west of London, Ontario. Farmers are also preparing for a possible wave of cases when migratory birds return in the spring.
In Quebec, avian flu has spread since April 2022 among wild birds in all regions, indicates the Ministry of Agriculture, Environment and Natural Resources.
Public health agencies in Canada, the United States and Europe agree that the risk to human health remains low, with cases almost always limited to direct contact with infected birds or contaminated environments. , such as chicken coops. Eating well-cooked poultry products is safe.
Scientists, however, are studying the virus closely. In a paper published last month, Canadian Food Inspection Agency scientists working at a lab in Winnipeg, where Canadian cases of H5N1 are eventually confirmed and genetically sequenced, examined the cases of 40 different wild mammals. The researchers found that the virus had undergone “critical mutations”, although the agency said the risks of spread to humans remained minimal.
“The spread of these viruses from wild birds to mammals might cause a potentially devastating pandemic if the H5N1 viruses mutate into forms capable of spreading effectively among mammalian species,” reads the article published in the journal at peer-reviewed “Emerging Microbes & Infections”.
The critical mutations discovered by the researchers relate to a part of the virus that helps it make copies of itself, adding to similar findings reported around the world. In 17% of cases, scientists found changes that gave the virus better advantages to replicate in humans.
But in an encouraging sign, the researchers wrote that the virus had not developed a strong preference for latching onto receptors in the nose, mouth and throat of a human being — the target of a influenza and the key to human infection.
The Public Health Agency of Canada said it takes the situation “very seriously” and has multiple surveillance networks to control and track flu viruses. With lessons learned from the COVID-19 pandemic, the agency was able to develop H5N1-specific plans across government departments.
