The UK Health Security Agency (UKHSA) said the individual, who lives in the South West of England, was infected after being in "very close, regular contact with a large number of infected birds".
The person is currently well and self-isolating and there is no evidence that the infection has spread to anyone else, the agency said.
As a precaution, the UKHSA swabbed the person involved and detected low levels of flu. Further lab analysis showed that the virus was the ‘H5’ type found in birds.
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It said this is the first human case of this strain in the UK, although there have been cases elsewhere globally.
The agency says the risk to the wider public remains very low, but it has urged the public not touch sick or dead birds.
In a statement, the health protection agency said: "Bird to human transmission of avian flu is very rare and has only occurred a small number of times in the UK previously.
"The person acquired the infection from very close, regular contact with a large number of infected birds, which they kept in and around their home over a prolonged period of time.
"All contacts of the individual, including those who visited the premises, have been traced and there is no evidence of onward spread of the infection to anyone else.
"The individual is currently well and self-isolating.”
Bird Flu in Lancashire
The UK has recently seen a large number of bird flu outbreaks, with a number of cases confirmed in Lancashire's wild bird populations.
There are currently 64 cases of avian influenza H5N1 in England, with disease control zones in force around Poulton-le-Fylde and Clitheroe.
The case in Clitheroe was first detected on November 26 and further testing has confirmed this to be a highly pathogenic strain (HPAI H5N1). All birds on the infected premises have been humanely culled.
Following a risk assessment, a 3km Captive Bird (Monitoring) Controlled Zone has been put in place surrounding the Clitheroe premises.
A day earlier, on November 25, cases were confirmed at a poultry farm near Poulton, where a 3km Protection Zone and 10km Surveillance Zone was declared and all birds culled.
Britain's largest ever Bird Flu outbreak
On December 21, the UK’s Chief Veterinary Officer, Christine Middlemiss, said the UK faced its largest ever outbreak of bird flu with more than 60 cases confirmed across the country since the start of November. Around half a million birds have been culled so far
Some strains of bird flu can pass from birds to people, but this is extremely rare, according to the UKHSA.
It usually requires close contact with an infected bird, so the risk to humans is generally considered very low.
Human-to-human transmission of bird flu is also very rare, the organisation said.
The UKHSA said that, at this point, it has not been possible to confirm that this is a H5N1 infection (the strain that is currently circulating in birds in the UK).
It said this is the first human case of this strain in the UK, although there have been cases elsewhere globally. The UKHSA has notified the World Health Organisation (WHO) as a precaution.
Professor Isabel Oliver, chief scientific officer at the UKHSA, said: "While the risk of avian flu to the general public is very low, we know that some strains do have the potential to spread to humans and that’s why we have robust systems in place to detect these early and take action.
"Currently there is no evidence that this strain detected in the UK can spread from person to person, but we know that viruses evolve all the time and we continue to monitor the situation closely.
"We have followed up all of this individual’s contacts and have not identified any onward spread."
Ms 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.
"We took swift action to limit the spread of the disease at the site in question, all infected birds have been humanely culled, and cleansing and disinfection of the premises is underway.
"This is a reminder that stringent cleanliness when keeping animals is important.
"We are seeing a growing number of cases in birds on both commercial farms and in backyard flocks across the country. Implementing scrupulous biosecurity measures will help keep your birds safe."
For contacts of an infected person who have the highest risk, the UKHSA contacts them daily to see if they have developed symptoms.
There is no vaccine for bird flu, but people can be offered anti-viral treatment after exposure to infected birds to stop the virus reproducing in their body. Swabs are also carried out on people even if they do not have symptoms.
Symptoms of bird flu
The main symptoms of bird flu can appear very quickly and include:
- a very high temperature or feeling hot or shivery
- aching muscles
- a cough or shortness of breath
Other early symptoms may include:
- stomach pain
- chest pain
- bleeding from the nose and gums
It usually takes 3 to 5 days for the first symptoms to appear after you've been infected.