Genetic tests carried out on the dead swan from Cellardyke, Fife, reveal that it was infected by a strain of the virus that is “almost an exact match” for the one found in dead swans on the island of Rügen in February.

The findings suggest that the Scottish case is the continuation of a bird flu outbreak that has swept across Europe rather than a new form of the virus, which some experts had feared.

“It’s reassuring to some degree,” said Professor Peter Openshaw, a virologist at Imperial College London. “The clade (strain of H5N1) that seems to be responsible for most of the virus spreading through Europe doesn’t seem terribly infectious to humans compared with the one that emerged in Vietnam.

“But it does seem almost inevitable that, one way or another, it will spread and repeatedly infect wild birds in the UK. This is something we are going to have to live with for a long time.”

Charles Milne, Scotland’s chief veterinary officer, yesterday announced that restrictions imposed on poultry farmers around Cellardyke could be lifted within a month if no further cases of bird flu emerge.

Milne confirmed that tests on 12 swans and two other wild birds found dead in Scotland had proved negative for H5N1, a virus that has killed more than 100 people worldwide.

However, tests on other wildfowl continued as laboratories were kept open throughout the weekend to deal with an influx of new reports.

Dead birds were collected by animal health officers from at least 22 sites in the surveillance area surrounding the initial case. A dead swan found in the river Test near Romsey, Hampshire, was also being examined for bird flu.

Zoos are considering vaccinating exotic bird species to protect them from the virus, while 10 pairs of breeding swans at the world-famous Abbotsbury swannery in Dorset have been put into an isolation unit indefinitely as a precaution.

Even the Queen has stepped up action. At Balmoral, a 7ft wire fence has been erected and a new secure henhouse is in place for her prized free-range chickens. A spokesman for Buckingham Palace confirmed that regal swans would not be exempt from a cull if bird flu spread to the south of England. The Queen has the royal prerogative to claim ownership of any mute swan in Britain, but she chooses to exercise this only over 1,200-1,500 birds on the Thames.

Most scientists believe that the Cellardyke mute swan, a species that rarely travels long distances, was infected by another wild bird migrating from the continent after a cold snap in February.

The swan was reported to the authorities 11 days ago, but delays in testing meant that confirmation that it had died from the “highly pathogenic” H5N1 virus did not come until last Wednesday.

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