A “dog flu” virus descended from bird flu is slithering towards the possibility of infecting people, scientists have warned.
A version of bird flu called H3N2 first infected dogs around 2006 and has since established itself in dogs and evolved into a mammalian-adapted form of bird flu.
Bird flu is highly contagious and deadly among birds, but has never been shown to sustain person-to-person transmission.
But scientists have long been concerned that if the avian flu virus is able to establish itself in a mammalian species, then it could develop into a strain that can jump from mammal to mammal, including humans.
A study by avian flu specialists at the China Agricultural University analyzed swabs from more than 4,000 dogs and found that the virus is now showing signs of an improved ability to recognize human cell receptors and an increased ability to replicate in cells. human cells.
The team says dogs could be the stepping stone species that bridges the significant anatomical gap between birds and people.
“Our results showed that canines may serve as intermediates for the adaptation of avian influenza viruses to humans,” the scientists write in their paper, published in the journal eLife.
Six dogs were deliberately infected with each of six known strains of H3N2 canine influenza in a laboratory, and all were found to be mildly ill. The most serious symptoms were fever, sneezing and cough.
British experts say the study is well conducted and offers insight into the role pet dogs can play as potential patient zero for a future ‘dog flu’ epidemic.
“The H3 strain of bird flu has evolved into a virus specific to dogs”
Professor James Wood, head of the department of veterinary medicine at the University of Cambridge, told The Telegraph that ‘it is quite clear’ that the H3 strain of avian flu has now evolved into a virus specific to dogs.
“Apparently the changes in the canine virus are better adapting it for transmission within mammals, as might be expected after such a long period in dogs,” he said.
He added that this could be good news for the potential zoonotic infection of people as it has not yet spread to humans, but warned that this could be because it has not yet reached the required mutation threshold.
“The virus does not appear to pose a particularly worrisome health threat to dogs. One might be more concerned about the long-term pandemic potential in other species such as humans,” said Prof. wood.
Professor Ian Jones, professor of virology at the University of Reading, told The Telegraph that the Chinese study provides evidence that the virus is “crawling” towards humans.
“It’s a data-rich paper that definitely shows that the newer viruses (clade 5) are more adapted to mammals than the original virus that jumped from an avian,” he said.
“But part of that is just the virus settling in the dog, thus inevitably becoming similar to the mammalian virus.
“At the moment I think these data deserve attention, but the case of a ‘threat’ is not clear.”
Professor Jones also said it was possible, with its current range of mutations, that the canine flu virus could continue to infect humans. There is no evidence of this yet, nor any reported cases of it.
People are not immune to the H3 family of flu viruses, the study authors warn, saying that antibodies from pre-existing flu vaccines and flu strains would not work against canine flu.
Professor Jones said this seems unlikely and that there may be pre-existing protection against disease, though not against infection as seen during the Covid pandemic.
The study only looked at the presence of canine flu in dogs living in China, but Professor Wood said if throat swabs were taken from other dogs around the world then he would expect it to be present globally.
“Other canine viruses have spread globally and it seems likely that this one may have already done so too. So I don’t think screening for any dogs moving from the US or China or elsewhere would be proportionate based on the evidence in the document,” she said.
“Canine Flu Checks and Tests Needed”
Both the authors and independent scientists said it was too early to introduce restrictions on human-dog dyads, but said enhanced surveillance and testing would be a prudent move.
“Continued surveillance coordinated with risk assessment for canine influenza viruses is needed,” the Chinese scientists write in their paper.
Professor Jones said regular screening, quarantine and testing for canine flu were still not justified by the threat revealed by the new paper.
However, he said that “it wouldn’t be a bad thing if rapid tests for canine influenza were added to other current diagnoses over time.”
“Dog control would be impossible in some countries and socially difficult in others, think of bovine tuberculosis and badgers in the UK.
“I think the obvious thing is surveillance and awareness in influenza referral centers of the dog-adapted sequences so that any human cases can be reported quickly.”