Three wild swans found dead in Dorset have tested positive for the H5N1 strain of bird flu.
The birds were found during routine surveillance in the Chesil Beach area of the county in the south of England.
The British Department for Environment, Food and Rural Affairs (Defra) has set up a control area, within which bird owners must isolate their flocks from wild birds
No disease has been found in domestic birds, and a programme of surveillance of wild birds is to be carried out. Defra has opted against culling because it may disperse birds and aid the spread of the disease.
Acting Chief Veterinary Officer Fred Landeg said today: "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."