A bird flu prevention zone in place since an outbreak at a farm near Louth has been extended until the end of February.
Poultry owners must continue to keep their birds indoors, or take appropriate practical steps to keep them separate from wild birds.
The zone covers England and similar declarations have been made in Scotland and Wales.
As previously reported, around 2,500 turkeys at a farm in Tetney were diagnosed with the H5N8 strain of avian flu on Friday, December 16.
All the birds at the farm were humanely culled by the Department for Environment, Food and Rural Affairs (Defra).
Defra has also imposed a country-wide ban on poultry shows and gatherings.
Chief veterinary officer Nigel Gibbens said: “The prevention zone means anyone who keeps poultry such as chickens, ducks and geese, even as pets, must take action to stop them coming into contact with wild birds to protect them from avian flu.
“Birds should be moved into a suitable building, or if that isn’t possible owners must take sensible precautions to keep them away from wild birds, like putting up netting to create a temporary enclosure and keeping food and water supplies inside where they cannot be contaminated by wild birds.
“Even when birds are kept indoors a risk of infection remains so keepers must also practice good biosecurity, for example by disinfecting footwear and equipment and washing clothing after contact with birds.”