A person working on a farm has contracted the human version of avian flu.
The UK Health Security Agency (UKHSA) said the individual "had close and prolonged contact with a large number of infected birds", but would not say where the farm was.
The person was "currently well and was admitted to a High Consequence Infectious Disease unit," it said.
It also said the risk to the wider public "continues to be very low" and that bird-to-human transmission of this kind was rare.
UKHSA routinely swabs people who have been in close contact with infected birds and, after confirming the transmission, said there was no evidence that the person had passed it on to anyone else.
Nevertheless, it said it had traced everyone the person had been in contact with and offered them antiviral treatment.
UK Chief Veterinary Officer Christine Middlemiss said: "While avian influenza is highly contagious in birds, this is a very rare event and is very specific to the circumstances on this premises."
She also said the farm had been thoroughly cleaned and that it was "a reminder that stringent biosecurity is essential when keeping animals".
Since 2021 there have only been seven cases of humans contracting bird flu, and there has never been an instance of bird flu being passed from human to human in Europe or the UK.
Andrew Gwynne, Minister for Public Health and Prevention, said the government had recently added the H5 vaccine, which protects against avian influenza, to its stockpile of vaccines as a precaution.