Bird flu has been confirmed at a second large commercial poultry premises near Swaffham.
A 3km protection zone and a 10km surveillance zone have been implemented around the business.
All poultry at the site will be humanely culled.
The return of the virus has led to the culling of farmed birds, including thousands of Christmas turkeys, which has been a “heartbreaking” blow to the poultry industry.
A mandatory national housing order has also been enforced to help stop the outbreak from growing, which means all keepers with more than 50 captive birds of any species, or any number of poultry kept to give away or sell eggs or poultry products, must be housed indoors.
Also, all poultry keepers must follow strict biosecurity rules, including cleaning and disinfecting clothing, equipment, and vehicles, and reducing the movement of people, vehicles, and equipment to minimise contamination.
It has also hit Suffolk farms near Lakenheath, Brandon, Honington and Woodbridge.
Defra says the current risk to human health remains low, and properly cooked poultry and poultry products, including eggs, are safe to eat.