2005-07-07-Bird fluUnderstanding Avian Influenza
Migratory birds could spread flu
By Betsy Querna
Each year, thousands of birds flock to the beautiful Qinghai Lake, high in northeastern China's Tibetan Plateau, to rest along their migration route or to breed and lay eggs. This year, some of those birds brought an extra passenger?the lethal strain of bird flu that has decimated poultry flocks in parts of southeast Asia and threatens to become a human pandemic.
As reported Wednesday in both the journals Science and Nature, scientists in China say they are concerned that because the virus now appears transmissible in migratory birds, it could spread to other areas of the world. Some of the birds that stop in Qinghai Lake fly to Europe, India, and Australia.
On April 30, scientists detected an outbreak in bar-headed geese, an Asian species that migrates over the Himalayas. The birds held their heads at a strange angle, staggered around, and shook with tremors. By May 4, more than 100 birds were dying each day on the lake, and scientists were rushing in to take samples of the birds' blood to figure out what was killing them. The blood samples revealed that the type of avian flu killing these birds, a variation of the H5N1 strain, most likely came from southern China or Vietnam?areas where the birds winter and where both poultry flocks and humans have been infected.
Here in the United States, there's no reason to be alarmed yet, says David Swayne, lab director of the Agriculture Department's Southeast Poultry Research Lab. He has been working with scientists in Alaska to test birds that migrate across the Bering Sea from Asia; so far all have tested negative for the H5N1 strain. "The thousands that died [at Qinghai Lake] won't migrate so they won't spread it," says Swayne. "The real danger could be those that are asymptomatic and migrate," and whether that is happening is still not known.
The virus is not yet easily spread between humans. It mutates often, however, and health experts around the world fear that one of those changes could turn it into a human pandemic.