Poultry farmers said the virus would have catastrophic effects on the industry as scientists predicted the worsening situation in Turkey made its arrival on UK shores increasingly likely.
The European Commission yesterday banned the import of untreated bird feathers from countries surrounding Turkey, which now means no live birds, meat or other bird and poultry products can be brought into the European Union from the region.
Yesterday five more cases of the deadly H5N1 bird flu strain were confirmed in people believed to have caught the virus from infected birds.
There are now nine confirmed cases in eastern Turkey and the capital, Ankara. Tests were also last night being carried out on 48 more people including several in Istanbul which, if confirmed, would be the first human cases of the disease in Europe.
As it became clear bird flu was now well established in Turkey and quickly spreading west, Russia advised its citizens against visiting there and Iran closed a border crossing.
One of Britain's top scientists also advised against travelling to the worst-hit regions but the Foreign Office said the risk of contracting bird flu remained small provided visitors avoided contact with birds at markets or farms.
Yesterday an international team of experts reached the original Turkish outbreak area in the east where a poultry cull is under way.
There remain no signs that the virus is mutating to allow human-to-human transmission, creating a long-feared pandemic, but fear is spreading rapidly.
The bird feather ban, which will apply to Azerbaijan, Armenia, Georgia, Syria, Iran and Iraq, adds to existing EU control measures introduced since the bird flu outbreak in Turkey last October.
Since then about 25,000 wild birds have been tested in the EU for avian flu and all tested negative.
But yesterday Professor Colin Blakemore, chairman of the Medical Research Council, said he believed there was a high chance that bird flu would spread to Britain.
He said he would not advise visiting parts of Turkey and other countries where there was known infection.
"Although it is not a cause for panic, there is certainly a cause for concern, preparation and vigilance," he said.
"The virus is being spread by migrating birds, which often don't show signs of infection.
"At the moment, bird flu is being passed to humans through direct contact – by touching the birds, holding them – or by dust entering the eyes and nose.
"There is no evidence that it is transmitted by eating the meat but it is certainly a possibility.
"The problem would be if it began being passed from person to person if the virus changed in some way which made it more infectious for people."
Liberal Democrat environment spokesman Norman Baker said: "It is very concerning that bird flu has reached so far west,
"Defra needs to prepare for the worst in this country. Now is the time to ensure that we are fully prepared for an outbreak in the UK."
Chief Veterinary Officer Debbie Reynolds said: "It's not inevitable that the UK will get avian flu. But obviously there is a risk."
She said that if avian flu did arrive in the UK commercial poultry keepers would be asked to house their birds wherever practicable.
Farmer Stephen Throup, who keeps 35,000 free-range hens at Nun Monkton, near York, said: "I am seriously concerned. We have invested a lot of money in the business and wonder what the future holds.
"All we can do is remain vigilant," added Mr Throup, who said that he had rigorously tightened biosecurity.
David Hugill, who runs a 13,500-bird free range unit at Faceby, near Northallerton, said: "Like other free range egg producers, we are already biosecure."
mike.waites@ypn.co.uk