Canine flu mutates into a virus that can spread to humans, scientists warn.
A strain of bird flu, H3N2, first infected dogs around 2006.
It has since established itself in canines and evolved into a mammal-adapted form of bird flu.
But researchers have now discovered that the virus can better recognize human cell receptors.
This development means the virus may be one step closer to overcoming the hurdle that has kept it from taking off in humans.
H3N2 influenza virus particles, colored transmission electron micrograph
The study, conducted at China Agricultural University in Beijing, analyzed swabs from more than 4,000 dogs.
It found that the virus now shows signs of being better able to recognize human cell receptors and replicate in human cells.
Write in the journal eLifesaid researchers: ‘Our results showed that canines can serve as intermediates for the adaptation of bird flu viruses to humans.’
Six of the dogs were intentionally infected with the known canine flu strains of H3N2.
But all were only mildly unwell, with the most serious symptoms including fever, sneezing and coughing.
To date, no case of human infection with a canine influenza virus has been reported worldwide.
However, experts cautioned that the study demonstrates the longer-term pandemic potential that H3N2 now poses to humans.
Professor James Wood, head of the Department of Veterinary Medicine at the University of Cambridge, said The Telegraph ‘it’s pretty clear’ the avian flu H3 strain had become a dog-specific virus.
He added: ‘The changes in the canine virus apparently mean that it has adapted better to transmit within mammals, as you would expect after such a long period in dogs.
“The virus does not appear to pose any particularly worrisome health threats to dogs — one might be more concerned about the longer-term pandemic potential in other animal species, such as humans.”
Meanwhile, Professor Ian Jones, a professor of virology at the University of Reading, said the study provides evidence that the virus “sneaks” to infect humans.
He added: “It’s a data-rich paper that certainly shows that the most recent viruses are more adapted to mammals than the original virus that jumped from a bird,” he said.
“But part of this is just the virus settling in the dog, inevitably becoming a mammal-like virus.
“At this point, I judge that this data deserves attention, but that the reason for a ‘threat’ is not clear.”
H3N2 is different from the H5N1 strain, which has fueled fears of another pandemic in the wake of Covid after sparking the world’s largest ever outbreak of avian flu.
An outbreak of bird flu cases in humans emerged in Cambodia in February and saw an 11-year-old girl die from the virus and her 49-year-old father tested positive for the H5N1 strain. Above, a worker carries chickens at a market in Cambodia’s capital Phnom Penh on February 24, 2023
In the UK, the Animal and Plant Health Agency, a division of DEFRA, assesses avian flu risk to humans on a weekly basis. The UK Health Security Agency also confirmed last month that it had updated its modeling scenarios of how an outbreak among humans in the UK could begin. All scenarios were considered to have an R-value — a measure of a virus’s ability to spread — between 1.2 and 2
Two weeks ago, a Chinese woman also became the first person ever to die from the H3N8 strain – one of the most common strains in birds.
Like other strains of bird flu, human infections can occur when enough virus gets into a person’s eyes, nose, or mouth, or is inhaled.
But earlier this month, officials in Canada confirmed that a dog in Ontario had died from the H5N1 strain days after contracting the virus from eating a dead wild goose that was infected.
However, the Canadian Food Inspection Agency assured that the risk to the general public “remains low.”
There have been a spate of human bird flu cases emerging in the early parts of 2023.
Earlier this year, a Cambodian man and his daughter were diagnosed with H5N1, another strain of bird flu.
Their cases sparked international concern, with many experts fearing citing the virus had mutated to better infect humans after ripping through the world’s bird population.
The bird flu outbreak, which began early last year, is the largest in history, affecting more than 200 million domestic birds worldwide, in addition to countless wild birds.
It has already leaked onto mammals such as minks, foxes, raccoons and bears, raising fears that it may soon acquire disturbing new mutations that could cause it to cause a human pandemic.
Further testing revealed that the H5N1 strain was not spreading rapidly among the world’s wild birds among the Cambodian family, but instead a variant known to spread locally in the Prey Veng province in which they lived.
Since the ongoing outbreak broke out in October 2021, there has been only one case of a Briton becoming infected with H5N1.
Alan Gosling, a retired engineer in Devon, became infected with the virus in early 2022 after his ducks, some of which lived in his home, became infected.
In the UK, the Animal and Plant Health Agency, a division of DEFRA, assesses avian flu risk to humans on a weekly basis.
The group is also looking at possible human vaccine candidates if the virus spreads to humans.
Current legislation prevents poultry and most captive birds from being vaccinated against the pathogen.
But health chiefs are now “actively” considering lifting the ban, in response to the escalating threat of avian flu.
The UK Health Security Agency (UKHSA) has currently set the threat level to level three as there is “evidence” of changes in the virus genome that could cause a “mammal infection”, it said.
Any “sustained” transmission of the pathogen from mammal to mammal would raise the threat level to four, while it would rise to five from human to human.
Bird flu outbreak: everything you need to know
What is it?
Bird flu is a contagious form of flu that spreads among birds.
In rare cases, it can be transmitted to humans through close contact with a dead or live infected bird.
This includes touching infected birds, their droppings or bedding. Humans can also get bird flu if they kill or prepare infected poultry to eat.
Wild birds are carriers, mainly through migration.
As they clump together to reproduce, the virus quickly spreads and is then carried to other parts of the world.
New species usually appear first in Asia, from where more than 60 species of shorebirds, waders and waterfowl migrate to Alaska to mingle with migratory birds from the US. Others go west and infect European species.
Which species are currently proliferating?
H5N1 and H3N8.
So far, the H5N1 virus has been detected in some 80 million birds and poultry worldwide since September 2021 – double the previous record set the year before.
Not only is the virus spreading rapidly, it is also killing at an unprecedented level, leading some experts to say it is the deadliest strain yet.
Millions of chickens and turkeys in the UK have been culled or quarantined.
But earlier this year, on March 27, the World Health Organization (WHO) also learned that a Chinese woman was the first person ever to die from the H3N8 strain.
The 56-year-old woman from southern Guangdong province was the third person known to be infected with the H3N8 subtype of bird flu, according to WHO.
While rare in humans, H3N8 is common in birds, but it causes little to no signs of disease.
It has also infected other mammals.
Can bird flu infect humans?
Yes, but only 868 human cases of bird flu have been reported to the World Health Organization since 2003.
The risk to humans is estimated to be ‘low’.
But people are urged not to touch sick or dead birds because the virus is deadly, killing 56 percent of people it manages to infect.