How worried should we be about bird flu?

What do the latest results mean and how likely is this new strain of avian H5N1 to start spreading in humans?

What do the latest results mean and how likely is this new strain of avian H5N1 to start spreading in humans?

This morning, the world woke up with some unsettling 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 turned up in mammals, including foxes and otters in Britain.

As usual on these shores, public health experts of the “Keep calm and carry on” persuasion were quick to hit the airwaves to reassure us. “The risk of influenza A [H5N1] infection to UK residents within the UK is very low,” said official government guidance issued by the UKHSA. Seven days of medical observation, along with “urgent investigation of any new febrile or respiratory illnesses” would only be necessary if someone you rubbed – a “confirmed contact”.

If you feel that déjà vu is descending, you are 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 sealed off where outbreaks in poultry have been confirmed. A deadly virus jumping from one species to another is never good news. Remember when the dissimilar H1N1 avian virus jumped from birds to pigs in 2008-9, for example.

So what is the real risk here? What do the latest results mean and how likely is this new strain of avian H5N1 to start spreading in humans?

The good news is that the virus has been doing the rounds for a long time in birds without mutating to spread effectively in humans. It was first reported in the Far East almost 20 years ago and has spread widely in poultry and wild birds worldwide.

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

Most importantly it says: “Poultry contact has been reported in the vast majority of human cases and there is no reported evidence of ongoing human-to-human transmission. No major changes have been detected in recently characterized viruses from human cases”.

That’s the exciting part.

A team of National Trust rangers clears dead birds from Staple Island, one of the Outer Group of Fern Islands, off the Northumberland coast, where Avian Influenza (bird flu) has had a devastating impact on one of the UK's worst.  known and important seabird colonies - Owen Humphreys/PA Wire

A team of National Trust rangers clears dead birds from Staple Island, one of the Outer Group of Fern Islands, off the Northumberland coast, where Avian Influenza (bird flu) has had a devastating impact on one of the UK’s worst. known and important seabird colonies – Owen Humphreys/PA Wire

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

The foxes and otters found in the UK are probably not infected because they certainly got infected not by mixing with other people, but by eating dead and infected bird carcasses. In other words, these infections will almost certainly die with the affected animal.

More worrying is what was found and reported recently in a mink farm in Spain.

‘We are playing with fire’

The story began there early last Autumn, when seagulls and dead strawberries started washing up on the coast of Galicia in the north-west of the country. Then in October, something unusual happened. At a fur farm a few miles inland, thousands of minks began dying from the same avian virus.

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

Within weeks, more than 4 percent of the mink had died of hemorrhagic pneumonia caused by the virus. Workers were given antiviral drugs and quarantined and the remaining 50,000 animals were promptly killed. 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 “consequence event” that could lead to the next human pandemic.

A paper published in Eurosurveillance two weeks ago said the virus found in the Spanish mink carried a “PB2” gene – one similar to the one found when bird flu jumped to pigs more than a decade ago.

“Our results also indicate that transmission of the virus may have occurred to other minks on the affected farm,” the authors wrote. There are persistent fears that such farms could act as incubators and, possibly, reservoirs for the virus – just as they have done with Covid and other zoonotic diseases.

“It didn’t happen this time, and maybe it wouldn’t happen, but this is one of the situations from which a new pandemic could arise,” said Marion Koopmans, head of the virology department at the Erasmus Medical Center in Rotterdam. “We are playing with fire.”

At present, most scientists think that the chances of the virus mutating enough to spread effectively in humans are unlikely. In the medium term, however, it’s a bit of a numbers game. Hundreds of millions of birds around the world are sick with the virus and there are hundreds of thousands of densely packed fur farms that could be infected and further mutate the bug – most of which are in China and south-east Asia.

‘This is what we don’t want to see’

Jeremy Farrar is director of the Wellcome Trust and was recently named as the next chief scientist at the WHO. He believes that the greatest risk of the next pandemic comes from intermediate animal species – creatures that could bridge the gap between birds and humans.

Responding to the report on the Spanish mink farm, he tweeted: “Personal opinion. The biggest risk [of] Avian/animal flu is the most dangerous flu pandemic [an] intermediate mom.”

According to Professor Koopmans, a member of the WHO team tasked with tracing the origins of Covid, the global distribution of H5 bird flu viruses has changed significantly since 2020.

“It now looks like it can spread between mammals, and this is something we don’t want to see. This means that a virus from the risk list has the opportunity to pick up mutations that could make it between people.”

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

Gosling, who survived, is the only confirmed case in Britain so far, although all workers on UK poultry farms are offered anti-virus and are carefully tested.

In addition to antivirals, there are human vaccine prototypes developed to fight H5N1 viruses if they begin to spread in humans. Some are being stockpiled but in the event of a sustained human outbreak, new vaccines specific to the strain of virus in question would have to be developed.

According to Matthew Baylis, the Oxendale chair of veterinary epidemiology at the University of Liverpool, the combined circumstances of a widespread bird flu outbreak and non-biosecure mink farms pose a clear risk.

“We worry about flu viruses that are a mixture and affect different hosts, as we saw with H5N1 and swine flu. [in 2009],” he said. “What we don’t want is this virus spreading widely [in birds] improve infecting people.

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

The biggest danger is that fur farms still exist. In 2021, there were 755 mink farms in the EU – down from a pre-pandemic figure of 2,900 – producing 27 million pelts per year.

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

Animal rights organizations have long called for fur farming to be banned, particularly on animal welfare grounds. Now public health experts are calling for change.

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

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

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

Prof Koopmans said screening factory farms where mink and other species such as pigs are kept is a sensible step, giving the chance of early detection to deal with the next virus spillover.

She warned, however, that the risk of a new and deadly virus can never be ruled out. “Lots of animals can move in and out of mink farms. Birds and bats fly in, cats and rats too. Even if people are very careful around these animals, nature can do the trick,” she said.

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