"With the experience of three flu pandemics in the last century we could be on the eve of a 21st century calamity," Byrne told a conference in The Hague, referring to major outbreaks in 1918, 1957 and 1968.

"While we have witnessed the deaths of millions of animals in Europe over the past couple of years, are we prepared for the deaths of 10 or 20 million of our fellow citizens arising from the mutation of a human and animal virus that we cannot control?" he asked.

World health officials told the conference on Thursday that the threat of animal diseases spreading to humans was increasing and governments must improve coordination to prevent them from becoming pandemic.

Disease outbreaks, like the fatal form of bird flu that keeps reappearing in Asia, cause huge economic losses, increase poverty, create panic and often provoke social and political insecurity, World Health Organization officials said.

The H5N1 strain of avian influenza, or bird flu, which has killed 28 people in Asia this year, worried officials from the moment it first struck in Hong Kong. Health experts have said it was just this kind of disease that could jump to humans and cause a global epidemic, like the 1918 flu that killed as many as 40 million people.

Even if an outbreak was limited to animals, Byrne made clear he was not convinced that EU states were capable to deal with it in the best way, saying pet animals may have to be culled to stamp out an outbreak.

"How do you explain this to a public which thinks that a vaccine or a pill is the cure for everything?" he asked.

An EU plan calls for urgent work on vaccines and antivirals that would involve both member states and industry, he said.

"The present situation is not satisfactory and gives rise to concerns about readiness for the next pandemic," Byrne said. "Our citizens will find it difficult to understand that we have a higher level of vaccine preparedness for animals than for people."

The Netherlands, the first European country to be hit by a form of bird flu that can infect humans, was forced to slaughter a quarter of all its poultry after an outbreak last year, which infected 90 people and killed one.