"Of course we are worried and we have to get used to the fact that avian flu is now spreading within the European Union," Zsuzsanna Jakab, head of the EU's Stockholm-based European Centre for Disease Prevention and Control (ECDC), told Reuters television.

"And I'm sure it will also spread to other countries beyond these five."

Hungary was awaiting results from a specialist laboratory in Britain to determine whether the H5 virus detected in three dead wild swans on Wednesday was in fact the H5N1 strain of H5. If confirmed, it would be the country's first case.

Other so far uninfected countries such as Sweden, Slovakia and the Czech Republic carried out tests but all results were negative.

Slovenia was testing for H5N1 in another three dead swans in which H5 had been found, while Germany discovered 10 more H5N1 cases, Greece detected an additional two and Austria also reported one more.

"Even with the most rigorous action we cannot assume that we will overcome this matter in a few weeks," German Agriculture Minister Horst Seehofer said in a televised speech.

Chancellor Angela Merkel said the German government had spent months preparing for an outbreak and was in a position to do everything necessary to combat it.

"There's no reason for a panic reaction but I would advise people to be careful," Merkel told ZDF television.

LOSS OF APPETITE

Europe's poultry industry has been hit hard by the arrival of the virus in the European Union. Poultry farmers in Italy, where chicken meat demand is said to have fallen 70 percent since Saturday, called on the government for tax breaks to help them survive the crisis.

The growing loss of appetite for poultry was evident in West Africa, where H5N1 outbreaks in Nigeria - the first in Africa - are worrying neighbouring countries.

"I don't eat chicken any more ... I also banned my family from eating chicken. I am afraid of what the television is telling us and I do not want to be contaminated," said archivist Leopold Assongba during a shopping trip in Cotonou, the economic capital of Benin, which lies west of Nigeria.

The virus, which has killed at least 91 people in Asia and the Middle East, has in the European Union been found only in wild birds so far. Transmission to domestic poultry could be devastating for the industry and human cases would spark alarm.

At present humans can contract bird flu only through close contact with infected birds, which is less likely to happen in Europe than in countries like Nigeria where poultry are everywhere and roam freely among people, experts say.

They fear H5N1 may mutate into a form that can be transmitted between people and cause a pandemic that could kill millions.

Slovenia said it would test people who had handled the dead swans only if they showed signs of illness, and so far none of the 30 people who had been in contact with them had.

Scientists explained why the majority of European Union cases had been found in swans, saying they were in fact not the species guilty of spreading the virus around the continent.

"Swans are highly susceptible to the virus - they drop dead. There are other birds which get infected but they do not become sick and they can spread the disease," said Dr Albert Osterhaus, a virologist at Erasmus Medical Centre in the Netherlands. He did not specify which species were the culprits.