Bird flu has been found at another four Norfolk farms - bringing the county's total to 14 cases this month in a deepening virus crisis.
Defra has confirmed a highly-pathogenic strain of avian influenza in commercial poultry near Watlington outside King's Lynn, near Mattishall outside Dereham, and at two sites near Attleborough - the ninth and tenth cases near the Breckland market town hotspot.
All poultry on the infected premises will be humanely culled, adding to a toll which also included 90,000 turkeys at a farm near Holt, confirmed on Monday night.
The accelerating epidemic in East Anglia has prompted a mandatory housing order to be enforced from today, requiring all captive birds across Norfolk, Suffolk and parts of Essex to be kept indoors, including free-range poultry and backyard hobby flocks, to stop the virus spreading.
Chief veterinary officer Christine Middlemiss said the lockdown was no cause for complacency, as biosecurity is estimated to be 20 times more effective than housing at limiting exposure to the disease.
She warned all bird keepers must maintain strict cleanliness and biosecurity procedures, including cleaning boots and clothing, preventing unnecessary visitors, and checking sheds and roofs for holes.
The nation's biggest-ever outbreak of bird flu is having a devastating effect on East Anglia's nationally-important poultry industry, as well as its treasured colonies of coastal and wetland birds.
More cases are expected as the winter return of migrating birds brings the potential for more outbreaks in the coming months.
The UK Health Security Agency advises that the risk to public health is very low and the Food Standards Agency says avian influenzas pose a very low food safety risk.
Poultry keepers and members of the public should report dead wild birds to the Defra helpline on 03459 33 55 77 and keepers should report suspicion of disease to APHA on 03000 200 301.
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