EU states have been urged to stockpile anti-viral drugs after confirmation that the bird flu virus found in Turkey is the H5N1 strain dangerous to humans.
Thousands of birds have already been culled in Turkey and Romania
The European Union should be ready for a potential flu pandemic, said Health Commissioner Markos Kyprianou.
The warning came after tests on dead birds in north-west Turkey confirmed the H5N1 strain. An outbreak in Romania is assumed to be the same, the EU said.
The H5N1 strain has killed more than 60 people in South East Asia since 2003.
However, of those only one is suspected to have died after catching the virus from another human.
Those who have been in the presence of dead or dying birds are most likely to become infected, and the chances of human-to-human transmission are still seen as very slim.
Speaking at a news conference, Mr Kyprianou advised seasonal flu vaccination for populations considered to be at risk and said governments should focus on stockpiling anti-viral drugs.
"What is important is that it does become a priority for all member states and that they make an investment for preparing for this event," he said.
Standard flu vaccines, normally given to young children, the elderly and sick, are unlikely to protect against bird flu.
However, scientists fear that the bird flu virus could mutate into a human pandemic strain if people suffering normal human flu are also infected with the H5N1 type.
Mr Kyprianou said an emergency meeting would be held on Thursday to discuss what measures to take.
The commissioner confirmed the virus found in the Turkish village of Kiziksa was the deadly strain, adding: "There is a direct relationship with viruses found in Russia, Mongolia and China."
He went on: "It is a highly pathogenic and aggressive virus and we in the European Union have to deal with that."
A 3km (two-mile) quarantine zone is to remain in place around Kiziksa for the next three weeks. Thousands of birds in the area have been culled.
Turkish authorities have urged calm, amid reports of people flocking to pharmacies to buy Tamiflu, the anti-viral believed to be most effective against bird flu.
Health Minister Recep Akdag said the situation was "under control", adding that Ankara was prepared for any possible flu pandemic.
Pharmacies in Romania have also reported a big surge in demand for vaccines against common flu.
The EU moved to ban all bird and poultry products from Romania on Thursday after tests on three ducks which died last week in the Danube delta confirmed the presence of the weaker H5 strain of bird flu.
Tests for the H5N1 strain are expected to be completed on the ducks on Friday.
The EU has also banned the import of live birds and feathers from Turkey until April.
BIRD FLU OUTBREAKS IN 2005 (H5N1 STRAIN)
The H5N1 strain remained largely in South-East Asia until this summer, when Russia and Kazakhstan both reported outbreaks
Scientists fear it may be carried by migrating birds to Europe and Africa but say it is hard to prove a direct link with bird migration