According to British environment officials a strain of bird flu has now been detected at three poultry farms at North Tuddenham, near Norwich, Norfolk. Norfolk has some of Europe’s biggest poultry farms.

The strain is suspected to be the H7 strain but further tests are being carried out; meanwhile 35,000 birds are being culled.

Experts say this particular strain is less of a threat to humans than the lethal H5N1 bird flu virus.

A poultry worker at the farm has contracted the infection in his eyes but three other poultry workers who showed signs of the illness do not have the disease, say health officials.

The farms are close to each other and veterinary authorities suspect other premises may also be infected.

A restrictive zone of 1 km has been placed around each farm.

The most likely source of the virus is thought to be from another farm or from the wild bird population.

Japan has apparently suspended poultry imports from Britain in order to prevent the spread of bird flu to domestic fowl but Britain’s environment ministry said it had not been informed of the suspension.

Britain has been in a state of high alert for bird flu since it discovered the H5N1 virus in a wild swan washed ashore at Cellardyke, near Fife in Scotland earlier this month.

The swan was Britain’s first case the H5N1 virus in a wild bird; the deadly strain has spread from Asia to Europe, the Middle East and Africa, and led to the death and culling of 200 million birds since late 2003.

According to the World Health Organisation the virus has infected 205 people and killed 113 since 2003.

Experts say although the disease is virulent among chickens the risk to the public remains “extremely low” and bird flu remains largely a disease of birds.

However, the fear from the outset has always been that the H5N1 virus could mutate and trigger a pandemic.