This extension has been enforced to help protect poultry and captive birds from catching the disease, according to the government's chief veterinary officer.
Under rules of the zone, poultry and captive bird-keepers are required to keep birds indoors, or to take appropriate practical steps in keeping them separated from wild birds.
While this prevention method covers England, similar measures have been enforced in Scotland and Wales, while a GB-wide ban on poultry shows and gatherings has been enforced.
The Department for Environment, Food & Rural Affairs (Defra) said that poultry-keepers must also practice good biosecurity to minimise the risk of infection spreading via items such as feed, clothing and equipment.
Prevention zone
"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," said Nigel Gibbens, chief veterinary officer.
"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."
The H5N8 strain of AI has been present in Europe for several weeks now, with a case in Wales recently confirmed. The first outbreak in England was reported on a turkey farm in Lincolnshire on 16 December, with swift action taken to control measures, including a 3km Protection Zone and a 10km Surveillance Zone around the infected premises.
"Recent H5N8 avian flu findings in wild birds and a backyard flock in Wales highlight just how essential it is to minimise contact between wild and captive birds and maintain good biosecurity to reduce the risk of infection," added Gibbens.
"We must continue to be vigilant and do all we can to protect against this highly pathogenic strain of the disease, which is why we are extending the Prevention Zone, have introduced a ban on poultry gatherings and continue to strengthen surveillance to understand the extent of infection in wild birds."
The news to extend the Prevention Zone was welcomed by the National Farmers' Union (NFU) Scotland, which said the precautions were a necessary step.
"The most recent outbreak in domestic birds in Wales appears to have occurred in a flock which was not adhering to the housing order, or taking any extra biosecurity measures to keep the flock seperated from wild birds," said NFU Scotland's policy manager, Penny Johnston. "The need for vigilance and a requirement to comply with strict biosecurity is a message for both commercial and backyard flock keepers.
"The threat posed by AI to our poultry population is growing, justifying the need for this extension and for all poultry keepers to recognise the importance of these measures and take all possible steps to protect their birds from disease."
Johnston highlighted that the discovery of AI in a Scottish bird of prey before Christmas was a reason for the Scottish public to play their part in preventing the spread. This can be achieved by supporting Scottish poultry producers in continuing to consume their products, as expert advice says that there is no risk to food in the UK.
"Secondly, any sightings of dead wild swans, geese, ducks or gulls, falcons or other birds of prey or five or more dead wild birds of other species in the same location, can be reported to the Defra helpine on 03459 335577 or details sent by email to defra.helpline@defra.gsi.gov.uk. Dead birds can be a sign of the disease and by notifying the Defra helpline, the public will help the industry response of this growing threat."