The confirmation by British laboratory tests that the H5N1 deadly strain of bird flu had reached mainland Europe for the first time, has prompted Romanian authorities to slaughter poultry and send in doctors.
The disease was confirmed in the Danube delta in three ducks found dead in the Romanian village of Ceamurlia de Jos.
European officials are now frantically preparing for a possible pandemic.
Experts have long feared feared that the H5N1 virus, which has already killed more than 60 people and caused the death of millions of birds in Asia since 2003, could mutate and spread easily among humans, creating a pandemic that might kill tens of millions of people.
According to Romanian Agriculture Minister Gheorghe Flutur, the latest outbreak was limited to Ceamurlia and Maliuc, 40 km (25 miles) to the north.
Immediately all 18,000 domestic birds in Ceamurlia were killed and the culling of Maliuc 3,000 poultry is already in hand.
Flutur says that on a 10-kilometre (six-mile) radius around Ceamurlia de Jos, the tests for bird flu are at present negative.
As a precaution authorities have intensified public health preparations, even though no human cases of bird flu have so far been reported from Romania or from Turkey, which has also confirmed H5N1 among domestic fowl last week.
Health Minister Eugen Nicolaescu has said that more doctors will be sent to the contaminated areas, to check on a house to house basis, how many people face the risk of being infected with the virus.
The Danube delta, near the Black Sea,is Europe's largest wetlands and is a major gathering point for migratory wild birds heading from Russia, Scandinavia, Poland and Germany as they head towards the warmer winters in North Africa.
However despite the Romanian assurances, Britain's chief medical officer Liam Donaldson, says that Britain is bracing itself for a pandemic of bird flu that could result in at least 50,000 deaths there.
Donaldson is echoing previous warnings suggesting the bird flu virus is capable of combining with a human flu virus and becoming easily transmissible.
He says historically, every 10 to 40 years, the flu virus mutates into a strain against which there is no natural immunity. In a normal winter flu kills more than 12,000 people in Britain.
Donaldson says as existing vaccines are unlikely to work in a bird flu pandemic, a new vaccine is desperately needed.
He estimates that there will be around 50,000 deaths from flu, but says it could be far higher.
At present there appears to be no immediate sign of Turkey's outbreak spreading.
According to a Health Ministry official the nine people under observation in hospital for possible bird flu had been allowed to go home as tests showed they were not infected.
Also, according to a senior veterinarian, it seems that early tests on 1,000 chickens that died in eastern Turkey after being sent from the infected northwestern area did not point to bird flu.
However officials have stopped the transport of poultry in the province.
Officials say that six southeastern counties in Romania have been cordoned off and vehicles leaving them are being disinfected at checkpoints. Poultry and pigs have been placed indoors, and the transport of live animals from the counties have been banned and fairs selling animals closed across the country.
Gabriel Predoi of the country's veterinary authority says the moves are in accordance with European Union decisions.
Late last week the European Commission asked governments on Friday to pinpoint areas most at risk and to keep poultry separate from wild birds, which carry the virus. EU veterinary experts are meeting on Thursday to review the situation.
The Romanian media reports that up to two million vaccine doses for regular flu have been sold in the past few days, even though it only protects people against the latest strain of human flu.
Pharmacists in Bucharest say they have exhausted all the flu vaccines in stock.
Bulgaria, which has borders to Romania and Turkey, plans to set up a bird flu crisis headquarters this week. The chief veterinarian Zheko Baichev, says they have stepped up border controls and increased surveillance over poultry farms along the Danube and Black Sea.
They have apparently carried out 500 blood tests on farm birds and also checked on 154 domestic and 100 wild birds found dead throughout the country.
Baichev says they have not as yet isolated the bird flu virus.
The H5N1 strain which first emerged in Hong Kong in 1997, caused the death or destruction of 1.5 million birds, sickened 18 people and killed six.
In 2003 it re-emerged in South Korea, and has since spread to China, Vietnam, Thailand, Laos, Indonesia, Turkey and Romania.
According to Alejandro Thiermann, an official of the Paris-based World Organization for Animal Health, rather than stockpiling antiviral drugs, more attention should be paid to fighting bird flu at its source in Asia.