An outbreak of bird flu among migrating geese in western China has opened a potential pathway for the disease to spread into India and Europe, according to studies published online yesterday by the journals Science and Nature.
The sick birds were first detected April 30 at Qinghai Lake, a breeding hub for bar-headed geese that migrate to Siberia, Myanmar, Australia, New Zealand and over the Himalayas into India - a possible jumping off point for transmission of the virus into Europe.
The movement of the H5N1 avian virus beyond its current center in East and Southeast Asia would pose a threat to poultry industries and increase the risk of more human infections.
But Chinese researchers said the outbreak, which has killed nearly 2,000 birds, might burn itself out before major seasonal migrations begin in September.
Scientists have long known that wild waterfowl can contract bird flu and pass the virus on to farm birds. But they believed wild birds were infected by mingling with sick farm poultry.
The two new studies showed that the virus can also pass between migratory birds, said Malik Peiris, a University of Hong Kong virologist and co-author of the Nature study.
Qinghai Lake plays a central role in the life cycle of birds that annually travel thousands of miles.
Migratory birds spend summer months feeding and mating at Qinghai before heading to Southeast Asia and other places for the winter. Birds that migrate toward India intersect migratory paths to Europe.
Until now, the virus has not been detected in species that migrate beyond the Far East.
Bird flu has circulated in Asia since 1997 and has killed or led to the culling of about 120 million birds; it has caused 61 human fatalities in Hong Kong, Thailand, Vietnam and Cambodia.
So far nearly all of the human cases have been traced to direct contact with infected birds, but World Health Organization officials warn that if the bird flu virus recombines with a human virus, it may convert to a form passed easily between people.
For previous articles about bird flu, go to baltimoresun .com/avianflu.