An American man has been left "severely ill" after catching an "unpredictable" virus which has never been seen before in humans.
The patient was hospitalised earlier this month with a high fever, confusion and respiratory distress.
It was confirmed he had H5N5, a strain of avian influenza typically found in wild birds such as ducks and geese.
Although the sufferer remains unidentified, the Washington State Department of Health described him as being "older" and having "underlying health conditions".
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It added that the man had a "mixed backyard flock of domestic poultry" at his home in Grays Harbor County on the southwest Pacific coast of the state.
It is understood that two of these birds recently died.
The property was also accessible to wild birds, with health officials saying either set of birds is "most likely" the source of his exposure to the virus.
As of last week, the man remained in hospital and the investigation is ongoing.
PICTURED: Workers in PPE collecting dead birds during a previous outbreak of avian flu
|PA
The Centres for Disease Control and Prevention has assured people the risk to the public is low.
No other person has tested positive for H5N5 and there is no evidence for person-to-person spread.
However, scientists have said that viral evolution can be "unpredictable".
H5N1 is more common in America, although it is still rare.
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The Centres for Disease Control and Prevention has assured people the risk to the public is low
|PA
The two strains differ due to a protein on the surface of the virus.
Since 2024, there have been 71 human cases of H5 bird flu in America, most of which only involved mild symptoms.
However, one man in Louisiana who had been raising chickens in his back garden died from the disease in January.
Since October, there have been 26 cases of H5N1 in the UK, 22 of which were in England.
A man in the US died from a similar strain of the disease earlier this year
|GETTY
Whole flocks of birds have to be culled when an outbreak occurs.
The Pirbright Institute's Professor Ian Brown, the former director of science at the Animal and Plant Health Agency, told the BBC that farmers should "prepare for the worst".
He added: "We had a very, very serious epidemic between 2021 and 2023, in excess of 350 outbreaks in the UK. That's off the scale.
"Now, it's really, really difficult to state what the final size of this outbreak would be, but the early signals are not great."
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