Cases like this are extremely rare and the individual probably became infected from very close contact with a sick or dead bird.
Experts say there is no evidence of onward spread and all close contacts of the person are being monitored.
The individual is currently well and self-isolating, and the risk to the public is very low.
Avian flu, also known as bird flu, is a type of influenza that spreads among birds. The UK has recently seen a large number of outbreaks and incidents of the H5N1 strain of avian influenza in birds across the country.
Human to human transmission of bird flu is very rare.
Some strains of bird flu can pass from birds to people but, again, is rare and requires close, prolonged contact.
Officials say the person in question got 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".
The virus they caught is the H5 type that is found in birds, but it is not yet clear whether it is the same H5N1 strain that has been causing recent outbreaks in poultry that have then had to be culled.
This is the first human case of this strain in the UK, although there have been cases elsewhere globally. Being a notifiable disease, The World Health Organization has been informed.
Prof Isabel Oliver, chief scientific officer at the UK Health Security Agency, 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."
The UK's chief veterinary officer Christine Middlemiss said: "We are seeing a growing number of cases in birds on both commercial farms and in backyard flocks across the country.
"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 under way. This is a reminder that stringent cleanliness when keeping animals is important."
Prof Ian Jones, who is an expert in viruses at the University of Reading, said there is no risk to chicken meat or eggs and no need for public alarm.
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