Bird flu has spread widely, infecting a range of species such as chickens, skunks, cows, foxes and polar bears, leading to renewed questions about the level of risk it poses to people, with a British Columbia teenager remaining in critical condition in hospital after being infected.
But it’s the recent jump to pigs that has experts on high alert, as pigs provide the ideal conditions for the virus to mutate, making it a potential threat to human health.
United States last month Health officials reported The first case of avian influenza A(H5N1) in a pig occurred on a back farm in Oregon, marking the first time the virus has been detected in pigs in the country. Days later, officials confirmed that a second pig at the farm had also tested positive.
“With every variant it jumps into, it increases the risk,” said Kerry Bowman, a professor of bioethics and global health at the University of Toronto. “But pigs are a species of particular concern. The risk has risen again.”
Pigs are of particular concern for the spread of bird flu because they can be infected with avian viruses and human viruses, which can exchange genes to create a new, more dangerous virus that can more easily infect humans.
“Pigs can act as a mixing bowl, as they can be infected with avian influenza and human influenza simultaneously. These things can recombine,” Bowman said, adding that this could lead to the emergence of a new influenza A virus with different characteristics.
These “mixing bowl” events have occurred in pigs in the past; Bowman said it is believed to have caused the 2009 influenza A (H1N1) pandemic.
currently, The risk of bird flu remains lowBut every time the virus jumps to a new variant, it increases the risk, Bowman said.
Earlier this month, health officials in British Columbia announced the first human case of bird flu in Canada, and the teenage patient remains in critical condition in hospital. It is still unknown how the teen was exposed to the disease, but the strain is linked to viruses found in flocks during an outbreak on poultry farms in British Columbia.
More recently, the US Centers for Disease Control and Prevention (CDC) on November 15 confirmed the presence of a highly contagious form of bird flu in a person in Oregon. The infected person is linked to a previous outbreak linked to a commercial poultry operation in the state, where 150,000 birds were confirmed to be infected with the virus.
On Monday, US health officials confirmed the presence of bird flu in Hawaii, the first case of the virus in a domestic flock in the state since the current outbreak began in 2022.
Human infection with avian influenza is rare and usually occurs after close contact with infected birds, other infected animals, or highly contaminated environments.
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But Bowman warned that this could change quickly if the avian virus found a suitable host to mutate into.
Commercial pig farming is the real concern
Because the virus was discovered in backyard pigs, it doesn’t pose a major threat right now, Bowman said, but the real concern is that it could spread on commercial pig farms.
“Industrial livestock is a nightmare. The animals are kept in incredibly cramped conditions. So it will spread very quickly in a commercial endeavour. The other thing that happens in commercial farming is pigs are transported and sold, so there’s even more reason for it to spread there.”
Levon Abrahamyan, a virologist at the University of Montreal, echoed Bowman’s concerns.
“Fortunately it was not a commercial pig farm,” he said. “The pig likely became infected from a wild bird. The risk is low at this moment.”
He explained that it would be very worrying if a large pig farm was found to be infected with bird flu. In this case, every effort should be made to locate the outbreak and eliminate the virus to prevent further spread.
Avrahamian said it is usually difficult for bird flu to spread from birds to humans or from pigs to humans.
This is because viruses contain surface proteins (key) that must match specific receptors on the surface of host cells (lock) to enter and infect the cell.
If the virus’s key doesn’t fit into the cell’s lock, it won’t be able to infect the cell, Abrahamian said.
He explained that in the case of bird and swine influenza strains, when two different strains (of birds and pigs) infect the same host, their genetic material can mix. This could create a new virus with a combination of ‘keys’ that might fit the locks of human cells more effectively.
He added: “This could be a radical change, and therefore the human immune system is not ready for this type of change.”
This is exactly what happened in 2009, during the H1N1 pandemic, also known as “swine flu.”
In this case Abrahamian said there was Genetic mixing From human, bird and pig viruses. The pigs served as mixing vessels, creating a new subspecies that could infect humans It created a global pandemic.
How to prevent the epidemic
There is no evidence of bird flu being transmitted from person to person so far. But if that happens, the ingredients for a potential pandemic may be present, scientists say.
Bowman said he is concerned that Canada is not doing enough when it comes to testing and surveillance.
“Bird flu is not going away and will continue to spread into more species,” Bowman said. “If we look at this within Canada, a lot of species have bird flu now, a lot of our wildlife has it, as well as native species and wild birds… and with every species it goes up.”
He stressed the need for more monitoring, testing and timely reporting.
The Canadian Food Inspection Agency has also tested milk for signs of H5N1 infection in dairy cows.
There has been no indication yet of the virus being present in Canadian cattle, but bird flu has infected several herds in the United States.
The Public Health Agency of Canada (PHAC) is testing wastewater for seasonal influenza in several cities and towns across the country, including Toronto. But it does not specifically investigate H5N1 avian influenza because “it is not possible to differentiate positive signals of wastewater from wildlife versus human or animal sources,” the agency told The Canadian Press in an email.
“We also need incentives for people who work in livestock farming, as many may not want to report because they don’t want to deal with the problem. So we need more reporting and we need more monitoring,” Bowman said.
Experts say concerns about the availability of bird flu vaccines are also growing. Currently, there is no bird flu vaccine available for general use in Canada, although some vaccines are available globally.
Angela Rasmussen, a virologist at the Vaccine and Infectious Disease Organization (VIDO) at the University of Saskatchewan, told The Canadian Press that Canada should consider stockpiling H5N1 vaccines, similar to the United States, rather than relying on agreements with manufacturers to supply them on demand.
This is because deployment of an H5N1 vaccine under current contracts could take three to six months.
However, PHAC said in an email to The Canadian Press that it does not stock H5N1 vaccines due to their limited shelf life, which is only up to two years.
In an email to Global News in July, PHAC said it had “proactively met with pandemic influenza vaccine suppliers (e.g., GSK, Seqirus, Sanofi) with whom we have a domestic or overseas vaccine manufacturing agreement to discuss pandemic influenza vaccine readiness.” Activities to guide steps that can be taken against bird flu.
– With files from Reuters and The Canadian Press
