Home Health Bird flu keeps spreading beyond birds. Scientists worry it signals a growing threat to humans, too

Bird flu keeps spreading beyond birds. Scientists worry it signals a growing threat to humans, too

by News Desk
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As the deadly avian flu continues to ravage bird populations around the world, scientists are tracking infections in other animals, including various types of mammals that are closely related to humans.

throughout the last year, Canadian When US official Highly pathogenic H5N1 avian influenza has been detected in a variety of species, from bears to foxes. In January, France’s National Institute of Standards announced that cats suffered severe neurological symptoms from the infection, with the virus showing genetic traits of mammalian adaptation in late 2022.

Of most concern, according to several researchers, was a recent large-scale outbreak on mink farms in Spain.

Last October, farm workers began noticing a spike in animal deaths. Sick minks experience a disastrous array of symptoms, including loss of appetite, excessive saliva, bloody noses, tremors, and lack of muscle control.

The culprit turned out to be H5N1, the first confirmed case of this kind of bird flu infection among farmed mink in Europe, the study notes. Published in Eurosurveillance this month.

“Our findings also indicate that transmission of the virus to other mink may have occurred on affected farms,” ​​the researchers wrote.

Eventually, the entire mink population was killed or culled, totaling over 50,000 individuals.

According to Michelle Wille, a researcher at the University of Sydney who focuses on the dynamics of wild bird viruses, this is a major shift as only sporadic cases have occurred among humans and other mammals in the past decade.

“This outbreak shows that the potential for mammal-to-mammal transmission is very real,” she said in an email to CBC News.

It was just one farm, and notably none of the workers who wore face shields, masks, and disposable overalls were infected.

But Dr. Isaac Bogotch, a Toronto-based infectious disease expert, said the current concern is that if the virus mutates to become increasingly infectious among mammals, including humans, it could be “lethal.” It can have devastating consequences,” he said.

“This is an infectious disease that can be an epidemic and a pandemic,” he said. “I don’t know if people realize how big a deal this is.”

Watch | An explosive bird flu hits the world’s bird populations:

‘Explosive’ bird flu surge hits global bird populations

The world’s bird populations have been devastated by a deadly strain of avian flu, wiping out poultry flocks and killing wild birds. Some researchers have warned that the virus could eventually become more infectious to humans and cause future pandemics.

H5N1 has a high mortality rate

Among birds, mortality rates for this highly pathogenic avian influenza strain can approach 100%, devastating both wild bird populations and poultry farms.

It is also lethal to other mammals, including humans.

The World Health Organization (WHO) has reported 240 cases of H5N1 avian influenza in the last 20 years in four Western Pacific countries including China, Cambodia, Laos and Vietnam. More than half of those infected died.

According to global WHO figures, over 870 human cases were reported from 2003 to 2022, resulting in at least 450 deaths. >50% fatality rate.

Bogoch said the reported death toll may be an overestimate, as not all infections are detected.

Also, most human infections appeared to be associated with people who had direct contact with infected birds. Real-world mink-to-mink transmission definitely suggests that H5N1 is “ready to emerge in mammals,” Wille said.

“A virus that evolved on mink farms and then transmitted to farm workers exposed to infected animals is a very likely pathway for the emergence of viruses capable of human-to-human transmission,” she said. I warned you.

Louise Monkla, assistant professor of pathobiology at the University of Pennsylvania School of Veterinary Medicine, explained that having an “intermediate host” is a common mechanism for viruses to adapt to new host species.

“And what is worrying about this is that this could lead to exactly this kind of adaptation, the kind of virus that is expected to allow these viruses to replicate better in other mammals like ours. It’s a scenario.”

A government worker wearing protective gear collects poultry for slaughter during an avian flu outbreak in Ivory Coast. More than 70 countries have reported cases this year, according to the World Organization for Animal Health.
Government workers in protective gear gather poultry for slaughter during an avian flu outbreak in Ivory Coast. In 2022, he will have cases reported in more than 70 countries, according to World Animal Health Organization. (Regnan Coola/EPA-EFE)

Both Surveillance and Vaccine Needed

Even more encouraging, the development of a flu vaccine is underway, giving humanity a head start against the well-known threat posed by bird flu.

Wille says that early outbreaks of H7N9, another avian influenza strain that caused hundreds of human infections in the early 2010s, resulted in the virus acquiring mutations necessary for ongoing human-to-human transmission. I mentioned that it raised similar concerns that it might.

“But a very aggressive and successful poultry vaccination campaign eventually stopped all human cases,” she added.

However, while some H5N1 avian influenza vaccines have been produced, Including Made in Canadathere are no options approved for general use in this country.

To avoid the potential threat this strain poses to human health, Bogotsch said continued surveillance and vaccine production must remain top priorities for both policy makers and vaccine manufacturers. said.

Dr. Jan Hajek, an infectious disease specialist at Vancouver General Hospital, also wondered if it was time to scale back global mink farming given the spread of viruses, from bird flu to the novel coronavirus. presented. SARS-CoV-2, the virus behind COVID-19.

“We’re closely related to minks and ferrets in terms of flu risk…if it’s spreading to minks and killing them, that’s a concern for us,” he said. .

2021, BC officials announce statewide closure of mink farmingsays farms can become reservoirs for the virus and represent an ongoing danger to public health. Close all mink farms and sell all rawhide by April 2025 is needed.

However, other states and many countries intend to continue operating mink farms.

“Is it responsible to have this kind of farming conditions where this kind of event can occur?” asked Monkula. “If we continue to keep this kind of farm, what can we do to make it safer?”

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