Thousands of Gressingham ducks will be culled after bird flu was discovered at a farm near Fakenham.
A highly pathogenic strain of avian influenza was found on January 4 in a commercial poultry premises near Fulmodeston.
Gressingham Foods, the UK's largest duck producer, has confirmed the farm reared birds for its supplier, Green Label Poultry.
Defra says all poultry on the infected farm will be humanely culled, while a 3km protection zone and a 10km surveillance zone have been enforced around the site.
A spokesman for Suffolk-based Gressingham Foods said: "We are working closely with local authorities and following their guidance.
"The welfare of our birds is an absolute priority, and we work to the highest standards in hygiene, biosecurity and animal welfare across all our farms."
It comes after four bird flu cases were confirmed at poultry farms in the Diss area during December - part of the UK's worst-ever epidemic of the disease, which has devastated the poultry industry.
There have been 272 confirmed cases in England since the outbreak started in October 2021, sparking the cull of more than three million birds across the country.
The recent cases illustrate the continuing threat from the disease - although the pace of the outbreak has slowed since its peak in autumn, when Norfolk recorded more than 40 cases in October alone.
Goverment vets have enforced strict biosecurity measures and a mandatory housing order requiring all captive birds to be kept indoors, ranging from backyard flocks to commercial free-range farms.
Fabian Eagle, a Swaffham poultry auctioneer who was also recently appointed as Norfolk County Council's cabinet member for growing the economy, said the latest case was another blow to a struggling duck sector which could leave significant shortages of eggs and breeding birds.
"The duck sector has been attacked from all angles," he said.
"Not only have they lost a lot of meat ducks, but it [bird flu] has also got into the breeding flocks, and particularly ducks for egg-laying. Duck egg flocks have been decimated.
"People are talking about a shortage of chicken eggs, but the shortage of UK duck eggs will be enormous.
"Some people have lost their own breeding flocks, and there is nowhere to replace them."
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