The UK has officially been declared “disease free” for bird flu after an isolated outbreak was contained at an East Anglian poultry farm in December.

The chief veterinary officer announced that the country has met international requirements to declare itself free from the H5N3 strain of avian influenza – but reiterated calls for all poultry keepers to remain vigilant for signs of the disease, which continues to circulate in Europe and remains a “real and constant threat”.

The UK has remained free of “highly pathogenic” strains of avian influenza since September 2017, but the “low pathogenic” strain returned to East Anglia in December 2019 when a confirmed case prompted the cull of 27,000 chickens at a commercial chicken farm in Athelington, near Eye.

Animal and Plant Health Agency put movement restrictions in place to limit the spread of disease and conducted investigations into the source and possible spread of infection – concluding that the most likely source was indirect contact with wild birds. Defra says a secondary cleansing and disinfection operation was completed on March 13.

Chief veterinary officer Christine Middlemiss urged keepers to remain vigilant for signs of disease and reiterated the need for good biosecurity at all times.

“Declaring the UK free from avian flu is an important milestone that will help our efforts to re-open export markets,” she said. “The case in December was met with swift action by the APHA and industry and I would like to thank everyone for their efforts in helping us to very effectively contain the disease.

“However, I urge all keepers to be vigilant – there is a constant risk of avian flu from wild birds and this will increase later in the year when winter approaches, temperatures fall, and migratory birds arrive in the UK.

“All poultry keepers should take steps to reduce the risk to their birds by maintaining good robust biosecurity at all times, such as cleaning footwear, feeding birds indoors, and minimising contact with wild birds. Building these simple actions into routines now can help prepare for any future outbreaks.”

• For the latest information and guidance on avian influenza, see the .GOV website.