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Bird flu risks: What you need to know as the ‘versatile’ virus continues to spread – National | Globalnews.ca

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As the deadly H5N1 avian flu continues to spread globally, wiping out sea lion colonies, decimating bird populations by the millions and even reaching Antarctica for the first time, concerns persist about its risks potential for human health.

The latest development came after the US Centers for Disease Control and Prevention (CDC) on Monday reported a human case of avian flu in a person who had contact with dairy cows in Texas, presumed infected with the virus.

“This highly pathogenic avian flu has been circulating around the world at a very high rate for several years now,” explained Matthew Miller, managing director of the study. director of the Degroote Institute for Infectious Disease Research at McMaster University.

However, there are serious concerns that this disease has never spread to dairy cattle, he said.

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Click to play video: “Bird flu virus spreads to mammals”


Avian flu virus spreads to mammals


“What makes this concerning in terms of the risk to humans is that we know that humans are at greatest risk of viruses entering them when they are near infected animals. And indeed, this case in Texas appears to come from a cattle ranch worker who was in close proximity to an infected cow,” he told Global News.

“This is a relatively new development that changes risk assessment.”

Although human cases remain rare, health experts warn there is an increased risk that bird flu will evolve to more easily infect humans.

Avian influenza, also known as bird flu, is an illness caused by influenza viruses that spread among wild aquatic birds and can infect domestic poultry and other animal species. These viruses are distinct from those that cause influenza in humans, but they are related.

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The H5N1 avian influenza virus first appeared in 1996 in southern China and has since caused avian epidemics around the world.

Since 2020, a variant of these viruses belonging to the H5 clade 2.3.4.4ba has caused an unprecedented number of deaths of wild birds and poultry in many countries in Africa, Asia and Europe. In 2021, the virus spread to the United States and Canada, and in 2022 to Central and South America, according to the World Health Organization (WHO).

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Globally, H5N1 has infected many mammals, including foxes, mountain lions, skunks, and black and brown bears in North America. Avian flu has already reached new corners of the world in recent years and is now present in penguins living in Antarctica and polar bears in Alaska.

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The virus typically infects the gastrointestinal tract of birds and is excreted when the bird defecates, Miller said.

“When there are ducks and geese migrating over pastures, for example, if those birds defecate, it can contaminate the soil, it can contaminate drinking water, which can lead to infection of other animals. Of course, in many cases infected birds can also die. And if scavenger animals eat these birds, that’s another way for them to become infected,” he explained.

What is the risk for humans?

Human cases of H5N1 are primarily due to zoonotic transmission through direct contact with infected birds (dead or alive) or contaminated environments. Human-to-human transmission is extremely rare, Health Canada said on its website.

The most recent death occurred last month in Vietnam, the WHO reported. A 21-year-old died on March 23 after testing positive for H5N1. The man had no history of contact with dead or sick poultry or people with similar symptoms. However, health officials said he may have trapped wild birds in his hometown.

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“In Canada, the risk to the general public is still very low,” Miller said.

However, he believes cases involving infected cow’s milk deserve “increased attention”, particularly from people whose professions expose them closely to wild animals and farm animals.


Click to play video: “Fighting Zoonotic Diseases in Ontario”


Fighting Zoonotic Diseases in Ontario


“Historically, the real problem with highly pathogenic avian influenza infections in humans is that, despite relatively low transmission rates, they can cause much more severe disease than a typical influenza infection,” he said. warned.

“Previous outbreaks of bird flu have resulted in mortality rates that are in some cases above 30 percent, which is extraordinarily high by viral standards. »

Another distinctive feature of this virus, he noted, is that unlike most seasonal flu strains that primarily affect human lungs, highly pathogenic avian flu can infect various organ systems in our body. In some cases, it can even reach the brain, causing serious complications such as encephalitis, which poses significant treatment problems.

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Should we be worried about milk?

On March 25, US federal authorities announced the detection of avian flu in laboratory samples taken from some infected cows in Texas and Kansas. Days later, federal officials said they had confirmed the virus in a Michigan herd and suspected additional cases in cows in New Mexico and Idaho.

Authorities said they believe the cows contracted the virus from wild birds, but transmission between cattle “cannot be ruled out.”

This is the first time the disease has been detected in dairy cattle, according to the American Veterinary Medical Association (AVMA).

Shayan Sharif, professor and associate dean of the Ontario Veterinary College at the University of Guelph, called the transmission “quite surprising” and “rather unexpected.”

“But this virus has proven to be quite versatile. It can do a lot of different things. And maybe we shouldn’t have been surprised to see this virus jump from birds to cattle,” he said.

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Click to play video: “Bird flu discovered in dead skunks”


Avian flu discovered in dead skunks


Sharif previously said that many infectious disease specialists were under the impression that the H5N1 virus could not be transmitted to livestock, but “many of our theories and assumptions turned out to be wrong.” So I’m very concerned about what this virus is capable of doing in the future. »

Miller also believes Canadian farmers are being more vigilant about their livestock in light of these cases. As spring arrives, migration will bring waterfowl back to these areas, increasing the risk.

However, Miller reassured there was no risk of contracting the virus from pasteurized milk.

“That’s why we pasteurize, to kill all kinds of germs that might be present in the milk. And that’s why pasteurization is so widespread and plays such an important role in preventing infections,” he said. “And, in general, there is no risk of contamination of meat products either. So it’s not something I think people need to worry about.

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How to prevent future outbreaks

Miller and Sharif emphasize that the most effective strategy for preventing widespread outbreaks of avian flu is to minimize its risks of transmission from animals to humans.

As Miller explains, the more opportunity the virus has to jump from animals to humans, the more likely it is to develop the ability to infect humans.

“Then it has the possibility of being transmitted between people. This creates a risk of widespread epidemics or pandemics. And fortunately, as far as we know, this virus doesn’t do that effectively, and we want to keep it that way. »

Sharif noted that because bird flu works similarly to COVID-19, many of the practices implemented during the pandemic can be applied here. This includes minimizing contact with infected animals, ensuring thorough hand washing and practicing disinfection wherever possible.

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Another strategy to help prevent an outbreak involved vaccination.

“We currently have no vaccination plans for poultry or livestock in Canada,” Sharif said. “But time will tell whether or not there will be a safe and effective vaccine available for poultry and livestock. »

– with files from Katherine Ward and Reuters from Global News



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