Is bird flu poised to become the next deadly pandemic?
That’s a question being asked with increasing frequency and urgency, especially with the recent jump of the H5N1 avian influenza to dairy cattle, and its rapid spread to farms across the U.S. (There are no known cases of infected cattle in Canada.)
As it stands, public health officials say the risk of humans being infected with bird flu remains very low. There is no threat to the food supply either, according to the Canadian Food Inspection Agency.
But all this has an eerie sense of déjà vu, at a time when the physical, social and political wounds of COVID-19 are still raw.
One can’t help but wonder if we’ve learned anything at all from the pandemic and whether we will be better prepared this time than last – for either a false alarm or the real thing.
Still, H5N1 is a very different beast than SARS-CoV-2.
The novel coronavirus emerged out of nowhere (well, a wet market in China to be more precise) and its potential for spread wasn’t taken all that seriously at first. By the time a serious response began, a global pandemic was well under way.
Avian influenza, on the other hand, has been simmering and mutating for decades.
H5N1 was first detected in a goose in Guangdong, China in 1996, and began to spread. The next year saw the first human infections, with 18 individuals in Hong Kong infected, six of whom died. This was a big deal because, until then, it was thought that H5 influenza viruses were unique to birds and could not infect humans. There were massive culls of poultry in Asia and the threat seemingly disappeared.
Then, the virus sprung up again in Asia in 2004, at a time when infectious-disease experts were most preoccupied with SARS. Still, there were a significant number of deaths among people infected by H5N1 in 2004 (54 out of 100 diagnosed individuals died), which raised alarm bells.
Earlier, in 2003, renowned virologist Robert Webster had written in the journal American Scientist: “The world is teetering on the edge of a pandemic that could kill a large fraction of the human population.”
But, despite the ringing alarm bells, the H5N1 virus dissipated, with sporadic cases being recorded in subsequent years. Since 2003, there have been 880 known human cases reported to the WHO by 23 countries, with more than half of those infected dying.
Over the years, the virus mutated and continued to spread from Asia to Europe, moving from domestic poultry to wild birds, and back again.
In December, 2021, H5N1 was detected on a farm near St. John’s, the first case in North America – likely spread by migratory birds. Since then, the continent has been ravaged – with 11 million poultry (including chickens, ducks and geese) culled in Canada and another 90 million in the U.S.
Wild birds are also dying in large numbers and spreading the virus to mammals that eat birds and scavenge – bears, seals, skunks, cats, and more. The carnage is unprecedented; in Argentina, 17,000 southern elephant seal pups were found dead from H5N1 infection on the shores of the Valdés Peninsula in January, representing 95 per cent of the pups born in 2023.
But it is the recent spread in cattle that is causing alarm. At least 33 dairy farms in eight U.S. states have H5N1 cases, but it’s not entirely clear how the flu virus is spreading – likely during transport, via milking machines, or food supplies. (In the U.S., cattle can be fed poultry waste, but that is not allowed in Canada.)
Humans have a lot of contact with cows, raising the possibility of transmission to people. There have been two cases in farm workers in the U.S. to date, and both of them were mild. There is little risk of spread in food, unless you drink raw milk. (Pasteurization works!)
What scientists really worry about is H5N1 jumping to pigs, because pigs are susceptible to both human and avian flu strains, making them ideal mixing bowls for the emergence of new variants that could spread in humans. (The pandemic H1N1 influenza strain of 2009 first emerged on a pig farm in Mexico.) We can’t wait for that to happen again.
This is not a time to panic, but to step up surveillance and prevention measures, like masking farm workers and even planning for the potential need for mass influenza vaccination (the good news being that we already have H5N1 vaccines).
H5N1 may become a pandemic. But it’s not certain, nor inevitable. With due diligence, we can reduce the odds, and lessen the potential for disaster.
As the saying goes, chance favours the prepared.
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