By Svetlana Kovalyova

MILAN, Oct 25 (Reuters) - Bird flu virus may become endemic in parts of Europe, with ducks and geese more of a vector for spreading it than previously thought, the U.N. said on Thursday.

"It seems that a new chapter in the evolution of avian influenza may be unfolding silently in the heart of Europe," Joseph Domenech, chief veterinary officer of the Food and Agriculture Organization (FAO), said in a statement.

The statement came after German scientists detected H5N1 in dead domestic ducks which had appeared to be healthy.

Avian influenza predominantly hits birds, but contact with sick birds is the most common way for humans to contract H5N1, which has been fatal in 204 of 332 cases since 2003. A few cases of human-to-human transmission have been recorded.

Health experts fear the deadly H5N1 strain could mutate and spark a pandemic. If the virus develops a way of transmitting among humans, the results could be devastating.

After Asia and Africa, Europe may become the third continent where the H5N1 strain could become endemic, the FAO said.

"Europe should prepare for further waves of avian influenza outbreaks, most probably in an east-west direction, if the virus succeeds in persisting throughout the year in domestic waterfowl," Domenech said.

FAO veterinary experts said they were particularly concerned about the Black Sea area where a high concentration of chickens, ducks and geese is comparable with virus-entrenched Asia.

FAO experts urged the European countries to boost their H5N1 monitoring and surveillance schemes in all regions with big duck and geese production, if it was confirmed that the H5N1 virus can persist in apparently healthy domestic ducks and geese.

"It could well be that there is more virus circulation in Europe than currently assumed," said FAO senior animal health officer Jan Slingenbergh.

"We are not saying that the virus is widely spread in European countries, in fact most of the countries are currently virus-free. But undetected localised virus spots in countries with significant waterfowl may pose a continuous risk," he said.