All 480 birds living on the site are set to be culled to limit the spread of the disease.
The UK’s bird flu threat was raised from “low” to “medium” around two weeks ago after avian influenza was detected in two swans in the Netherlands.
An outbreak was confirmed at a small commercial premise near Deal in Kent on Monday, the government said.
“Immediate steps have been taken to limit the risk of the disease spreading and all remaining poultry and captive birds at the farm will be culled,” Christine Middlemiss, the UK’s chief veterinary officer, said.
The business does not suppy poultry meat or eggs to the commercial food chain, Ms Middlemiss said.
The Department for Environment, Food and Rural Affairs (Defra) discovered positive antibody results in three birds at the farm out of 20 sampled in a routine avian influenza surveillance programme.
Public Health England (PHE) has said the threat to public health from bird flu is very low.
“Avian influenza remains an uncommon infection in humans,” Dr Gavin Dabrera from PHE said following news of the outbreak in Kent.
The consultant in acute respiratory infections advised people not to touch any sick or dead birds, and to wash hands thoroughly with soap following contact with any animal.
The outbreak at the Kent site involved avian influenza of the H5N2 strain, according to the government.
The Food Standards Agency has said this strain does not pose a food-safety risk for UK consumers. “The wider risk posed by avian influenzas through the food chain is very low,” a spokesperson added.
An investigation is underway to find out the origins of the outbreak at the Kent farm.
After the bird flu cases were detected in the Netherlands in October, the UK raised its virus threat level from migratory birds.
The swans were confirmed to have H5N8 avian influenza, according to the UK’s four chief veterinary officers.
Last December, thousands of chickens were culled at a commercial farm in Suffolk after a number were found to have bird flu.
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