The outbreak, which occurred in a protected reserve in western China, known as Lake Qinghaihu, became apparent on April 30 in wild bar-headed geese. In less than a month nearly 1,500 birds had succumbed to the disease, Yi Guan of the University of Hong Kong and his colleagues report in Nature, and many more died in the following weeks, including birds of three other species. When the researchers analyzed samples of the virus collected from the dead animals, they discovered that it is closely related to the H5N1 strain that made people in Thailand and Vietnam sick. "This outbreak may help to spread the virus over and beyond the Himalayas," the team notes, "and has important implications for developing control strategies."
A report published in Science, meanwhile, indicates that four sub-strains of the H5N1 virus taken from the dead wild birds are particularly virulent. Jinhua Liu of China Agricultural University in Beijing and his colleagues exposed mice and chickens to them and found that within three days of exposure all but one of the 16 test animals died. Because the lake is a breeding center for birds that return to Southeast Asia, Siberia, Australia and New Zealand, the potential for spreading avian flu outside of its Asian stronghold is high, the new reports suggest. Both teams call for increased surveillance of poultry farms to stave off the disease before it becomes entrenched in more bird populations around the world.