Global Courant 2023-04-26 07:55:30
New Canadian research has found that certain strains of the avian flu, which are responsible for the deaths of millions of birds worldwide, can spread quickly and “efficiently” between ferrets in a laboratory setting, raising alarm bells that it could potentially cross species into humans as well .
Bird flu — more commonly known as bird flu — has been spreading across Canada among farmed birds since 2021, with more than 7.5 million birds as of last week, according to the Canadian Food Inspection Agency (CFIA).
Human infections of bird flu are rare and usually occur after close contact with infected birds through poultry farms or live bird markets.
The real concern would be if the virus could make the full jump to humans and then spread from person to person — a possibility scientists are keeping an eye on.
In this new study, published in a preprint this week, researchers from the Public Health Agency of Canada, CFIA, SickKids Research Institute and the University of Manitoba, among others, report that a specific avian flu strain was able to spread easily among mammals in a lab setting.
In particular, they found that samples of H5N1 highly pathogenic avian influenza (HPAI), taken from a red-tailed hawk, could spread “efficiently” in direct contact between ferrets, the mammal most often used to assess the risk of a virus reaching humans. . transfer to humans.
“Highly pathogenic” refers to the virus’ ability to cause disease, underlining how dangerous H5N1 is.
When research is presented in a preprint, it means it has not yet been peer-reviewed. The research is currently being reviewed for publication in the peer-reviewed journal Nature Portfolio.
Bird flu has been devastating wild and farmed bird populations around the world for years. Last November, it was announced that HPAI has led to the deaths of more than 52 million birds in the US by 2022, either from contracting the disease or through culling to prevent the spread of the virus.
The virus has also been reported in mammals, such as mountain lions, red foxes, skunks and black bears, although this study is the first time mammal-to-mammal transmission of HPAI has been observed.
Previous studies have shown that H5 subtypes generally do not transfer well between mammals, and researchers noted that recent studies of currently circulating H5N1 strains have caused only mild infection in ferrets, which is a far cry from the lethal outcomes researchers have predicted. observed in this latest study.
“Our study determined that certain, as yet uncharacterized, genetic signatures may be important determinants of mammalian adaptation and pathogenicity of these viruses,” researchers wrote in the study.
To study the virus, researchers isolated five different H5N1 HPAI strains from infected wild animals in Canada, including three birds and two red foxes that had died from the virus.
They found that the virulence of the virus itself varied widely depending on the particular isolate, with the red-tailed hawk sample causing the most serious and deadly disease in the ferrets. Ferrets introduced into red fox viral samples also experienced severe and fatal disease. Researchers found that there were particularly high levels of viral replication in the upper and lower respiratory tracts of the mammals.
Direct transmission between ferrets was clearly indicated in the case of the red-tailed hawk virus.
Researchers also created a cell culture consisting of primary nasal, tracheal and human airway epithelial cells obtained from healthy human subjects, to test how the virus would interact with these isolated cells. The red-tailed hawk viral sample replicated fastest within these cell types compared to others.
The study notes that researchers were “struck by the high virulence and efficient transmission” of the red-tailed hawk viral samples among ferrets, as that particular strain was of avian origin, unlike the virus taken from red foxes.
They theorized that “passage through multiple animal species” might have contributed to that species’ “enhanced transmissibility”.
“This is a scenario that is likely to be seen with increasing frequency as the outbreak continues in wildlife species,” the study said.
Currently experiencing Canada numerous bird flu outbreakslargely within commercial poultry farms, although it appears to be circulating at a lower level than in 2022.
Bird flu outbreaks have been reported in Ontario, Quebec, Nova Scotia, New Brunswick, British Columbia and Alberta in 2023, with Ontario, Quebec and Alberta all reporting at least one infected property in April.
Earlier this month, CFIA reported that there had been a rare case of a domestic dog contracting bird flu in Oshawa, Ont. The dog reportedly became infected with H5N1 after chewing on a wild goose and subsequently died.
“The number of documented cases of avian influenza H5N1 in non-avian species, such as cats and dogs, is low, despite the fact that this virus has caused major avian outbreaks worldwide in recent years,” according to a CFIA press release.
“Based on current evidence in Canada, the risk to the general public remains low and current scientific evidence suggests that the risk of a human contracting avian flu from a pet is small.”
It’s still unclear why certain bird flu strains are more virulent or transmissible than others, but researchers say this new evidence supports the idea we should now keep an eye on.
“Ongoing surveillance of circulating HPAI A (H5N1) viruses in various species, including humans, should be a top priority to rapidly identify viruses that may have pandemic or outbreak potential in mammals,” the preprint states.
