As the spread of bird flu continues, why the latest jump in pigs raises concerns – National
Bird flu has spread far and wide, infecting species as diverse as chickens, skunks, cattle, foxes and polar bears and raising questions about how much of a risk it poses to humans as a BC teenager remains in critical condition in hospital after contracting the virus.
But the latest jump to pigs has experts very wary, as pigs provide the perfect conditions for the virus to mutate, making it dangerous to human health.
Last month, health officials in the United States reported the first case of avian influenza A(H5N1) in a pig on a backyard farm in Oregon, the first time the virus has been found in pigs in the country. Days later, officials confirmed that a second pig at the farm was also found to be infected.
“With every species that jumps into it, it increases the risk,” said Kerry Bowman, a professor of bioethics and global health at the University of Toronto. But pigs are the most worrisome species. The danger has risen again.”
Pigs represent a particular concern for the spread of bird flu because they can be infected with both bird and human viruses, which can mutate their genes to form a new, more virulent virus that can easily infect humans.
“Pigs can act as a mixing bowl, as they can have bird flu and human flu at the same time. And these things can recombine,” said Bowman, adding that this could lead to the emergence of a new influenza A virus with different properties.
These “mixing bowl” events have occurred in pigs in the past; it is believed to be the cause of the 2009 A(H1N1) influenza pandemic, Bowman said.
Right now, the risk of bird flu remains low, but Bowman said every time the virus jumps to a new strain, it increases the risk.
Earlier this month, health officials in British Columbia announced the first case of bird flu in Canada, with a young patient in critical condition in hospital. It's still unknown how the teenager was exposed, but the strain is related to viruses found in flocks during outbreaks on BC chicken farms.
Recently, the US Centers for Disease Control and Prevention (CDC) on November 15 confirmed the most dangerous form of bird flu in Oregon. The infected person has been linked to a previous outbreak linked to a poultry operation in the province, where the virus was confirmed in 150,000 birds.
And on Monday, US health officials confirmed the presence of bird flu in Hawaii, the first case of the virus in the domestic flock in the state since the current outbreak began in 2022.
Human infection with bird flu is rare and usually occurs after close contact with infected birds, other infected animals or highly contaminated areas.
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But that could change quickly if the bird virus finds a suitable host to mutate into, Bowman warns.
Raising commercial pigs is a real concern
Because the virus was discovered in a backyard pig, it doesn't pose a major threat yet, but the real concern is its spread to commercial hog farms, Bowman said.
“Industrial livestock is a nightmare; the animals are kept in incredibly harsh conditions. So it would spread very quickly in commercial endeavor. Another thing that goes on with breeding and selling pigs is that they are transported and sold, so there are many reasons for it to spread there,” he said.
Levon Abrahamyan, a virologist at the University of Montreal, echoed Bowman's concerns.
“Luckily it wasn't a pig farm,” he said. “The pig may have been attacked by a wild bird. The risk is low right now. “
He explained that it would be very worrying if a large pig farm was found to be infected with the avian influenza virus. If so, every effort should be made to localize the outbreak and eradicate the virus to prevent further spread.
Abrahamyan said that it is often difficult for bird flu to jump from birds to humans or from pigs to humans.
This is because viruses have surface proteins (key) that must match certain receptors on the surface of host cells (key) to enter and infect the cell.
If the virus's key doesn't match the cell's key, it can't infect the cell, Abrahamyan said.
In the case of avian and swine flu, when two different strains (from birds and pigs) infect the same host, their genes can mix, he explained. This can create a new virus with a combination of “keys” that can enter the locks in human cells more effectively.
“And that can be a big change, and the immune system is not ready for that kind of change,” he added.
That's exactly what happened in 2009, during the H1N1 pandemic, also known as “swine flu.”
In this case, Abrahamyan said there is a mix of genes from human, bird and pig germs. Pigs acted as mixing vessels, leading to the creation of a new subtype that could infect humans, and caused a global pandemic.
How to prevent an epidemic
There is no evidence of human-to-human spread of bird flu so far. But if that happens, it's the ingredients for a potential pandemic, scientists say.
Bowman said he is concerned that Canada is not doing enough about testing and surveillance.
“Bird flu is not going away and will continue to spread to many animals,” Bowman said. “When we look at this in Canada, many species have bird flu now, many wild animals have it as well as domestic species and wild birds … and for all species this raises.”
He stressed the need for more monitoring and timely inspections and reporting.
The Canadian Food Inspection Agency has also been testing milk for signs of H5N1 in dairy cows.
There have been no signs of the virus in Canadian cattle, but bird flu has hit many flocks in the United States.
The Public Health Agency of Canada (PHAC) is testing wastewater for seasonal flu in many cities and towns across the country, including Toronto. But it doesn't specifically test for H5N1 bird flu because “it's not possible to distinguish positive signs of contaminated water from wildlife versus human or livestock sources,” the agency told The Canadian Press by email.
“We also need incentives for people who work with livestock, as many do not like to report because they do not want to deal with the problem. So we need more reporting and we need more scrutiny,” said Bowman.
Concerns about the availability of bird flu vaccines are also growing, experts say. Currently, there is no bird flu vaccine available for public use in Canada, although there is one available worldwide.
Angela Rasmussen, an epidemiologist at the University of Saskatchewan's Vaccine and Infectious Disease Organization (VIDO), told The Canadian Press that Canada should consider keeping H5N1 vaccines, like the US, rather than relying on agreements with manufacturers to provide them when needed.
This is because moving the H5N1 vaccine under existing contracts can take three to six months.
However, PHAC said in an email to The Canadian Press that it does not vaccinate against H5N1 because of its limited shelf life, only up to two years.
In an email to Global News in July, PHAC said it is “closely engaging with pandemic influenza vaccine providers (eg, GSK, Seqirus and Sanofi) with whom we have an agreement for domestic or offshore vaccination to discuss pandemic influenza vaccine readiness.” to know about the measures that can be taken against bird flu.”
-From files from Reuters and the Canadian Press
