A new Canadian study warns that mutations in the avian influenza virus, H5N1, are causing new symptoms in some mammals exposed to it.
Researchers found the virus in 40 Canadian carnivores, such as red foxes, striped skunks and mink that likely devoured the carcasses of dead or sick birds.
If the H5N1 virus is not so new that it can occasionally infect mammals, the symptoms observed this time around are. Instead of causing the usual respiratory symptoms, the virus caused neurological symptoms; Thus large amounts of H5N1 antigens have been detected in the brains of some animals. Heart and lung injuries were also noted.
The researchers also discovered that the virus has undergone mutations that could make it more capable of infecting mammals.
Wild birds appear to have introduced this strain of virus to Canada in 2021-2022. Such “critical” mutations were noticed soon after their arrival, the authors of the study, published in the scientific journal Emerging Microbes & Infection, warn of the need to monitor the virus.
“Influenza A viruses are constantly evolving, thus accumulating adaptive mutations that facilitate virus replication, cross-species transmission, and pose pandemic risks to humans and animals,” the study authors wrote.
Some viruses adapt specifically to a host, Dr. Levon Abrahamian, a professor in the Animal Molecular Virology Laboratory of the University of Montreal’s College of Veterinary Medicine, recalls. Others can mutate quickly and thus quickly adapt to a new host.
“This is the case with coronaviruses and influenza viruses,” he said. This is why these viruses are so important to emerging viruses.”
Another study, conducted in the United States, found H5N1 in 57 live mammals, including foxes and raccoons. Fifty-three of them had neurological symptoms, including seizures, tremors, balance problems, and loss of fear of humans.
It’s these neurological symptoms that “concern us,” Dr. Abrahamian said, adding that the same symptoms can befall a cat or dog that comes into contact with a dead or sick bird.
The researchers recall that the neurological symptoms observed in raccoons, skunks, and Canadian minks are similar to those seen in seals and foxes infected with H5N8. A recent study in the United Kingdom showed that this virus may have been transmitted directly to foxes and seals by swans it was kept in captivity with.
It cannot therefore be ruled out, the authors of the Canadian study specified, that the mutations that H5N1 undergoes now allow it to be transmitted from mammal to mammal, for example through breast milk or simply during close contact in the hide.
This transmission risk remains unclear, the researchers said, because the virus strain responsible for the current outbreak lacks two characteristics that could facilitate it.
By contrast, the H5N1 variant that infected two Arctic foxes and an Ontario fox had a (rare) mutation that could make the virus more virulent in mammals, allowing it to evade part of its host’s immune system response and thus cause more severe disease.
“This virus can infect mammals, but it needs a longer and broader evolutionary process to adapt to continuous transmission between mammals,” said Dr. Abrahamian. There is no evidence of direct mammalian transmission.
He adds that the risk of transmission to humans is “very small” at the moment.
“The virus needs time and opportunity to become transmissible from mammal to mammal, from wild animal to domestic animal and from domestic animal to human,” he said. It is a long and haphazard process. But monitoring is very important, no doubt.”
