How concerned should we be about bird flu?

What do the latest findings mean, and how likely is it that this new strain of avian H5N1 could begin to spread among humans?

This morning the world woke up to some disturbing news. According to the UK Health Security Agency (UKHSA), the H5N1 “bird flu” virus, a deadly pathogen that has killed hundreds of millions of birds worldwide, has emerged in mammals including foxes and otters in Britain.

As is traditional on these shores, public health experts of the “keep calm and carry on” persuasion rushed to the air to reassure us. “The risk of influenza A [H5N1] infection among UK residents within the UK is very low,” the official government guidance issued by the UKHSA said. Only if he was infected by someone he rubs shoulders with – “a confirmed contact” – would a seven-day medical observation be warranted, along with “an urgent investigation of any new febrile or respiratory illness”.

If you feel a sense of déjà vu descending, you’re not alone. We haven’t yet been asked to sing “Happy Birthday” twice while washing our hands, but large parts of Norfolk and Lincolnshire have been cordoned off where outbreaks in poultry have been confirmed. A deadly virus that jumps from one species to another is never good news. Remember when a not dissimilar avian H1N1 virus spread from birds to pigs in 2008-9, for example.

So what is the real risk here? What do the latest findings mean, and how likely is it that this new strain of avian H5N1 could begin to spread among humans?

The good news is that the virus has been circulating for a long time in birds without mutating to spread efficiently in humans. It was first reported in the Far East nearly 20 years ago and has spread to become common in poultry and wild birds around the world.

“From 2003 to November 25, 2022, 868 confirmed human cases and 457 deaths from avian influenza were reported to the World Health Organization. [WHO] from 21 countries,” says UKHSA.

It is important to add: “The vast majority of human cases have reported contact with poultry and there is no reported evidence of sustained person-to-person transmission. No major changes have been detected in newly characterized viruses from human cases.”

That’s the encouraging part.

The National Trust ranger team removes dead birds from Staple Island, one of the outer group of the Farne Islands, off the Northumberland coast, where the impact of avian influenza (bird flu) is having a devastating effect on one of the best in the UK.  Known and Important Seabird Colonies - Owen Humphreys/PA Wire

The National Trust ranger team removes dead birds from Staple Island, one of the outer group of the Farne Islands, off the Northumberland coast, where the impact of avian influenza (bird flu) is having a devastating effect on one of the best in the UK. Known and Important Seabird Colonies – Owen Humphreys/PA Wire

But worryingly, the virus has now been found in mammals, along with genetic mutations that, in the cautious language of science, carry “public health implications.”

Foxes and otters found to be infected in the UK are probably not a cause for concern in themselves because they almost certainly became infected not by mixing with others, but by eating the carcasses of dead and infected birds. In other words, these infections almost certainly die with the animal in question.

More worrisome is what has recently been found and reported on a mink farm in Spain.

‘We are playing with fire’

The story began early last fall, when dead seagulls and gannets began to appear off the coast of Galicia, in the northwest of the country. Then, in October, something unusual happened. At a fur farm a few miles inland, thousands of mink began to die from the same avian virus.

Scientists believe that conditions on the farm, where tens of thousands of animals were kept in densely packed pens, had allowed the virus to mutate and spread among mink.

Within weeks, more than 4 percent of the mink had died of hemorrhagic pneumonia caused by the virus. The workers received antiviral drugs and were quarantined and the remaining 50,000 animals were quickly euthanized. Fortunately, none of the farm workers were infected.

Experts say what happened at the mink farm in the Galician city of A Coruña is exactly the kind of “side event” that could lead to the next human pandemic.

An article published in Eurosurveillance two weeks ago said the virus found in the Spanish mink carried a mutation in the “PB2” gene, similar to that found when bird flu jumped into pigs more than a decade ago.

“Our findings also indicate that further transmission of the virus to other mink on the affected farm may have occurred,” the authors wrote. Current fears are that such farms could act as incubators and perhaps reservoirs for the virus, just as they have with Covid and other zoonotic diseases.

“It didn’t happen this time, and it may not happen, but this is one of the scenarios where a new pandemic could start,” said Marion Koopmans, head of the virology department at the Erasmus Medical Center in Rotterdam. “We are playing with fire.”

For now, most scientists believe the chances of the virus mutating enough to spread efficiently in humans are unlikely. However, in the medium term, it’s a bit of a numbers game. There are hundreds of millions of birds around the world sick with the virus and there are hundreds of thousands of densely populated fur farms that could become infected and further mutate the virus, the vast majority of which are in China and Southeast Asia.

‘This is something we don’t want to see’

Jeremy Farrar is director of the Wellcome Trust and was recently named as the next WHO chief scientist. He feels the biggest risk from the next pandemic comes from animal species in between, creatures that could bridge the gap between birds and humans.

In response to the report on the Spanish mink farm, he tweeted: “Personal view. higher risk [of] devastating pandemic flu is avian/animal flu that infects [an] intermediate mammal.

According to Professor Koopmans, a member of the WHO team tasked with tracing the origins of COVID-19, the global distribution of H5 avian influenza viruses has changed significantly since 2020.

“Now it looks like it can spread between mammals, and this is something we don’t want to see. This means that there is a possibility that a virus on the risk list will acquire mutations that could make it transmissible between humans.

The only recorded human case of bird flu so far in the UK was duck keeper Alan Gosling, who contracted the virus last year at his home in Devon. The 79-year-old man tested positive during a routine swab after his flock of Muscovy ducks at his home in Buckfastleigh, Devon became infected.

Gosling, who survived, remains the only confirmed case in Britain to date, although all infected British poultry farm workers are offered antivirals and are thoroughly tested.

In addition to antivirals, there are prototype human vaccines that have been developed to combat H5N1 viruses should they begin to spread among humans. Some are in storage, but in the event of a sustained human outbreak, new vaccines would have to be developed that are specific to the virus strain involved.

According to Matthew Baylis, Oxendale Professor of Veterinary Epidemiology at the University of Liverpool, the combined circumstances of a widespread outbreak of bird flu and non-biosecure mink farms present a clear danger.

“We are concerned about influenza viruses that are a mixture and affect different hosts, as we have seen with H5N1 and swine flu. [in 2009],” he said. “What we don’t want is this virus that is circulating massively [in birds] to get better at infecting people.

“Eventually we might see one of these [mutations] That’s really serious.”

The biggest risk is the continued existence of fur farms. In 2021, there were 755 mink farms in the EU, down from the pre-pandemic figure of 2,900, producing 27 million pelts a year.

Most of the remaining farms are located in Finland, Poland, Lithuania and Greece. Spain is a tiny player with just over 20 facilities, almost all in Galicia. China and Southeast Asia present the greatest concern.

Animal rights organizations have long called for a ban on fur farming, mainly on animal welfare grounds. Now public health experts are calling for a change.

“I think the risk to public health is so high that it outweighs any benefits of having these farms,” said Elisa Pérez, a virologist at Spain’s Animal Health Research Center.

Dr. Pérez, a specialist in zoonotic diseases, which jump from a non-human host to a person and vice versa, questioned the safety of fur farms in Spain, noting that mink continue to escape on a regular basis.

She said: “Even if we make a facility biosecure, there is still a risk of transmission between mink and human workers, so authorities need to consider whether it is in the public interest to maintain these reservoirs of potential infection.”

Prof Koopmans said screening factory farms that house mink and other species such as pigs is a sensible step, offering the prospect of early detection to deal with the next spreading virus.

However, he cautioned that the risk of a deadly new virus emerging can never be ruled out. “Many animals can come in and out of mink farms. Birds and bats fly, cats and rats too. Even if people are very careful with these animals, nature can do the trick,” she said.

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