The government found the deadly H5N1 strain of bird flu in three wild swans on Thursday and warned poultry owners to protect their flocks.
The European Commission said the cases at a bird sanctuary in Dorset meant the EU's usual control area had been established around the premises.
Within the zone, poultry cannot be moved, except directly to slaughterhouses and the hunting of wild birds is banned.
"While this is obviously unwelcome news we have always said that Britain is at a constant low level of risk of introduction of avian influenza," Fred Landeg, Britain's acting Chief Veterinary Officer, said in a statement.
Britain's first case of the strain was in a wild swan found dead in Cellardyke in Scotland in 2006 and there have subsequently been outbreaks at poultry farms in eastern England, most recently in November 2007.
Nick Blayney, president of the British Veterinary Association, said surveillance played a critical role in tackling the disease.
"In this case vigilance would seem to have enabled the arrival of the disease to have been promptly identified.
"Domestic flock owners, not only in the vicinity but countrywide, are reminded of the need to protect their birds by following biosecurity guidelines...and to continually monitor their birds' health," Blayney said in a statement.
VIGILANCE
In the latest incident, no disease has been found in domestic birds and a surveillance programme is being carried out in the local wild bird population, the Department for Environment, Food and Rural Affairs (Defra) said.
