Bird flu restrictions have been imposed across Norfolk, Suffolk and parts of Essex following a string of outbreaks in poultry and wild birds.
The country's deputy chief veterinary officer has declared an avian influenza prevention zone (AIPZ) across the region to try to stop the virus spreading further.
From midday on Tuesday, it is a legal requirement for all bird keepers in Norfolk, Suffolk and parts of Essex to follow strict biosecurity measures.
Bird owners with more than 500 birds will need to restrict access for non-essential people on their sites, and workers will need to change clothing and footwear before entering bird enclosures.
The restrictions come into force after the disease was detected at 10 premises earlier in September, as well as several reports in wild birds.
Some birds had to be culled as officials planned to visit about 1,200 homes and businesses close to the outbreaks.
The UK's deputy chief veterinary officer Richard Irvine said: "This means that all bird keepers in the region must urgently take action now to both prevent disease getting into flocks and it spreading any further.
"Whether you keep just a few birds or thousands, you are now legally required to introduce stricter biosecurity standards on your farm or small holding.
"It is in your interests to do so in order to protect your birds from this highly infectious and devastating disease.”
The UK Health Security Agency said the risk to the general public's health was "very low", as it is primarily a disease that affects birds.
The Food Standards Agency added that the outbreaks pose a "very low food safety risk", as long as poultry and poultry products are cooked properly.
The restrictions will be in place until further notice and do not apply to people who keep house birds.
What do the restrictions mean for bird keepers?
The avian influenza prevention zone (AIPZ) means bird keepers in the affected regions must:
Clean and disinfect clothing, footwear, equipment and vehicles before and after contact with poultry and captive birds – if practical, use disposable protective clothing;
Reduce the movement of people, vehicles or equipment to and from areas where poultry and captive birds are kept, to minimise contamination from manure, slurry and other products, and use effective vermin control;
Keep records of mortality, movement of poultry and poultry products and any changes in production;
Thoroughly clean and disinfect housing on a continuous basis;
Keep fresh disinfectant at the right concentration at all farm and poultry housing entry and exit points;
Minimise direct and indirect contact between poultry and captive birds and wild birds, including making sure all feed and water is not accessible to wild birds;
Prevent access by poultry to ponds and watercourses and ensure that birds are kept in fenced or enclosed areas.
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