Outbreaks of bird flu have been confirmed at two poultry farms in Lincolnshire.
The Department for Environment, Food and Rural Affairs (Defra) said the cases were at commercial breeders.
A protection zone of almost two miles (3km) and an eight-mile (10km) surveillance zone have been declared around both sites.
All birds on the premises will be humanely culled, Defra said.
The first case of the highly pathogenic avian influenza (HPAI) H5N1 was confirmed at a site in Gainsborough on 5 December.
A day later a second outbreak was reported at a farm near the village of Sudbrooke just outside Lincoln.
The protection zone measures restrict the movement of birds, meat and eggs in the area.
The virus spreads through birds’ droppings and saliva, or through contaminated feed and water.
Scientists say the current risk to humans is low.
Transmission from birds to humans is rare and there has been no sustained human-to-human transmission.
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