The first known case of bird flu in a sheep anywhere in the world has been found on a Yorkshire farm.
The case was identified in milk testing as part of routine surveillance of livestock on the unnamed farm, where avian influenza H5N1 had been confirmed in poultry.
Here, The i Paper takes a look at everything we know about this case, and breaks down how worried we should be.
Has the case been contained?
The single infected sheep was humanely culled and no further infection was detected in the remaining flock, the Government has said.
This has raised hopes that the case has been contained and there will be no further infections – at least for now.
“While the risk to livestock remains low, I urge all animal owners to ensure scrupulous cleanliness is in place and to report any signs of infection,” said Christine Middlemiss, the chief veterinary officer.
“Strict biosecurity measures have been implemented to prevent the further spread of disease,” she added.
Given that other mammals, such as goats, pigs, foxes and cattle, have been infected with bird flu, the case in a sheep is not particularly surprising, scientists said.
And the fact that the virus appears not to have spread between sheep is also encouraging, they argue.
What does this tell us about the spread of bird flu?
Scientists have said that this latest infection provides further evidence that avian flu continues to spread, after five years of elevated levels.
The more species that are infected with bird flu, the greater the risk of it mutating into a form that can infect and spread easily between humans.
This hasn’t happened yet, but if it does it is likely to lead to a pandemic, scientists warn.
“The infection of the sheep is not that surprising given the reports of infection in other mammals – including humans – who have been in contact with infected birds,” Professor Paul Hunter, of University of East Anglia, told The i Paper.
CHESHIRE - NOVEMBER 04: Turkeys run free in a barn area on November 04, 2022 in Cheshire, United Kingdom. Due to the largest outbreak of Avian Flu in the UK, bird keepers will be required to keep their livestock inside to minimise the risk of transmission from the wild bird population. The UK produces between 9-10 million birds to be consumed at Christmas and there are fears that the situation will lead to a shortage this year. (Photo by Nathan Stirk/Getty Images)
The latest infection in Yorkshire provides further evidence that avian flu continues to spread, scientists say (Photo: Nathan Stirk/Getty Images)
“So far in humans there has not been any person-to-person transmission and if that remains the case then there will be no human pandemic.
“But the virus is evolving as a result of reassortment – when two distinct flu viruses infect the same cell and produce progeny that is a mix of both parent viruses.
“So, it certainly remains a possibility. And if one such progeny acquires the ability to transmit easily person to person then another pandemic is on the cards,” Professor Hunter added.
Colin Butter, Associate Professor in Bioveterinary Science, University of Lincoln, added: “There is little immediate threat to humans from isolated infections of sheep, as normal cooking of meat and pasteurization of milk readily kills the virus.
“However, it will be important to understand if sheep can transmit the virus to other sheep as any further spread would allow genetic mutation and inter-species contact that might eventually lead to transmission into other species, including humans.”
Could this spark a human pandemic?
Experts say the sheep case provides further evidence that bird flu continues to evolve which, in turn, increases the risk of the virus turning into a human pandemic.
But for now, their primary concerns remain the high number of cases in wild bird and poultry populations around the world and the spread of flu within US cattle, where the virus is being transmitted between cows.
This is thought to be the first time bird flu has been passed between animals of the same species, other than between birds.
Scientists say this means the virus can spread much more quickly through cow populations, from which it is more likely to evolve into a strain that can be passed easily between humans – creating the risk of a new pandemic.
Professor Christina Pagel, of University College London, said: “The next pandemic is more likely to be a flu one than not.”
Professor Steve Griffin, of Leeds University said “it’s impossible to say for sure” whether the H5N1 bird flu virus will become pandemic in humans “but it seems to be being given every possible chance to do so at the moment.”
“The sheer scale of the disease in animals, the range of species it’s infecting, and the rate at which mutations [that increase the transmission risk to humans and mammals] are being detected is genuinely both very different to past history and deeply concerning,” he told The i Paper.
“And the Trump administration is ignoring a widespread epidemic in livestock, poultry, and wild animals and birds and not preventing human contact. H5N1 may be everywhere, but the inaction in the US feels incredibly worrying at the moment.”
If bird flu does become the next pandemic, there is considerable uncertainty about how serious that would be.
“I am really struggling to even suggest a best guess. Somewhere between not much worse than seasonal flu and as bad as Covid,” suggests Professor Hunter.
“On the plus side, it would not take anywhere near as long to get vaccine rolled out as we saw during the Covid pandemic and that would undoubtedly reduce mortality at least in people who took up the offer of vaccine,” he said.
That’s because scientists already know a lot about flu vaccines and have existing ‘human H5 flu vaccines’ – based on the current H5 avian influenza virus – to start from.