The UK has suffered its third worst outbreak of highly pathogenic avian influenza (HPAI) with 100 cases reported during the 2025/6 season.

England has borne the brunt of the cases, recording 79 H5N1 HPAI, with 9 cases found in Scotland, 7 in Wales and 5 in Northern Ireland. A further case of low pathogenic H5N1 was detected through zonal surveillance.

Almost 4 million birds lost

More than 3.8 million birds have been culled or died as a result of the outbreaks, with chickens and turkeys bearing the brunt. Although the numbers are low, 40% of the duck breeder population was affected by bird flu in the last season and 7% of turkeys. Around 73% of cases have been large commercial farms with more than 1,000 birds with the remaining 27% found in backyard flocks. East Anglia has been particularly badly hit due to the density of poultry.

Gordon Hickman, head of the Department for Environment, Food & Rural Affairs’ (Defra) exotic disease control division, said that while the 2025/6 season had seen substantial losses, the decision to put in housing measures much earlier than in previous years seems to have successful.

Waterfowl the biggest culprit

Hickman said waterfowl continued to be the main reservoir of avian influenza. Of the 930 birds that tested positive, 914 were found to have the H5N1 strain across 91 counties and 48 species.

Speaking to delegates at the British Pig and Poultry Fair, Hickman urged producers to report dead wild birds, especially in East Anglia, stressing there would be comeback on the farmer if they tested positive.

He added the avian influenza virus continued to mutate and reassort, with the virus completely different from 2020/21. Recent outbreaks of highly pathogenic H5NX (mainly H5N1) clade 2.3.4.4b have been Europe, Asia, Americas and Antarctica, with only Australasia relatively unaffected.

Hickman touched on the spillover of the virus into livestock in the US but said there was no evidence this had got into the UK’s dairy herd following substantial bulk milk testing. But there continue to be cases in other mammals, including otters, seals, rats and foxes in parts of the world.

Biosecurity, biosecurity, biosecurity

Biosecurity continued to be key to stopping the virus from spreading and he urged producers to remain vigilant to ensure that wild birds and rats couldn’t spread it on farm.

Results of the UK’s vaccination programme in turkeys would be published later this summer although he stressed the vaccine would not be available this year: “We have learned a lot from the trial… but it is important to note that vaccination is not a substitute for poor biosecurity,” he added.

Trade barriers remain an issue, especially in Third Countries.