UK detects first H5N1 bird flu case in sheep, raising livestock spread fears

The UK's first case of H5N1 bird flu in sheep has been confirmed in Yorkshire, prompting authorities to step up efforts to prevent large-scale outbreaks similar to those seen in US livestock.

The infection was detected through routine surveillance of livestock on a site where avian influenza had already been confirmed in captive birds, the Department for Environment, Food and Rural Affairs said on Monday.

While UK officials have downplayed the risk to both livestock and humans, scientists and authorities are urging precautionary measures to prevent widespread transmission as observed in US poultry and cattle.

Many different mammals have died of the H5N1 bird flu virus across the globe including bears, cats, dairy cows, dogs, dolphins, seals and tigers.

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"The case was identified following routine surveillance of farmed livestock on premises in Yorkshire where highly pathogenic avian influenza (H5N1) had been confirmed in other captive birds," Britain's government said in a statement.

There have been cases among humans that have ranged in severity from no symptoms to, in rare cases, death. But there has not yet been any confirmed transmission between humans.

The sheep that tested positive was a ewe with signs of mastitis, an inflammation of breast tissue, and no other clinical signs, the statement from the British government's Department for Environment, Food and Rural Affairs, and the Animal and Plant Health Agency said.

Ed Hutchinson, professor of molecular and cellular virology at MRC-University of Glasgow Centre for Virus Research, said the fact that the sheep's milk also tested positive suggested parallels with the ongoing H5N1 outbreak among dairy cows in the United States.

Bird flu has spread among U.S. dairy cattle since March 2024.

He added, however, at the moment there was no evidence of ongoing transmission from the sheep and the case appeared to have been contained.

The ewe was culled and no further infection was found in the rest of the flock.

Britain's rural affairs ministry has introduced surveillance of livestock on premises where bird flu has been confirmed in captive birds following the outbreaks among dairy cows in the United States.

"Globally, we continue to see that mammals can be infected with avian influenza (H5N1)," Dr Meera Chand, emerging infection lead at the UK Health Security Agency, said.

"However, current evidence suggests that the avian influenza viruses we’re seeing circulating around the world do not spread easily to people – and the risk of avian flu to the general public remains very low."

With inputs from agencies