A conservation group said on Thursday that there was little evidence to back the view that migrating wildfowl were spreading bird flu and that eastern Europe's outbreak probably stemmed from poultry imports.
"As the year draws to a close, millions of wild birds have flown to their wintering sites across Asia, Africa, Europe and the Americas without the widely predicted outbreaks of H5N1 bird flu associated with their migration routes," BirdLife International said in a statement.
"The most obvious explanation is that migrating wild birds are not spreading the disease," said Dr Michael Rands, Director and Chief Executive of BirdLife.
The bird flu virus has killed nearly 70 people in four Asian countries since 2003 leading to mass culls of birds.
Officials say the H5N1 virus could spread to new countries through migratory birds from China, Mongolia, Vietnam and Russia -- which have reported major outbreaks.
The avian flu has been discovered in Romania and Ukraine and bird tissue samples were sent to Britain and elsewhere to determine whether an outbreaks there is H5N1.
But BirdLife said no "smoking gun" had been detected among wild birds in the region.
"The limited outbreaks in eastern Europe are on southerly migration routes but are more likely to be caused by other vectors such as the import of poultry or poultry products. The hypothesis that wild birds are to blame is simply far from proven," said Rands.
"Wild birds occasionally come into contact with infected poultry and die: they are the victims not vectors of H5N1 bird flu," he said.
BirdLife said banning the movement of poultry and related products from infected areas and restricting the global trade in captive birds were the best prevention methods.
"Migratory wild birds were blamed for spreading bird flu west from Asia, yet there's been no spread back eastwards, nor to South Asia and Africa this autumn," BirdLife said.
The H5N1 strain has not been detected in Africa yet but experts say uncovering it in the region's rural areas will be difficult because of poor logistics and already high mortality rates among the continent's backyard chickens.