Researchers in China have confirmed that the bird flu virus can spread between wild birds, raising fears that migratory species could carry the virus across Asia and beyond.
In parallel studies published online today (6 July) in Nature and Science, the researchers report that the H5N1 virus has killed at least 1,500 migratory birds in a nature reserve in western China since April.
Although H5N1 has been reported in dead wild birds before, they were found close to poultry farms affected by the virus, suggesting the wild species could have picked up the infection from domestic poultry. The Lake Qinghai reserve, however, has no poultry farms nearby.
Several bird species — the bar-headed goose, the great black-headed gull and the brown-headed gull — that visit the lake to breed have been affected.
The researchers warn that infected birds could spread the virus to others when they fly south towards Myanmar and over the Himalayas to India on their annual migration, which will begin in September.
So far, there have been no official reports of bird flu in South Asia.
The authors of the Nature paper, led by Y. Guan of the Chinese Joint Influenza Research Center, say there is a danger that the birds could also spread H5N1 along migratory routes to Europe.
Both teams found that the strain of H5N1 infecting birds on Lake Qinghai carries similar genes to strains that have infected domestic poultry in China and parts of South-East Asia since 2003.
The team publishing in Science, led by George F. Gao, of the Chinese Academy of Sciences, used the virus isolated from birds on Lake Qinghai to infect mice and chickens in the laboratory.
The chickens all died within 20 hours of infection. Seven of the eight mice infected died within three days.
Lake Qinghai is one of the most important breeding sites for migratory birds that spend the winter months in India, South-East Asia and Tibet.
|Map of China, with|
Qinghai province in red
Photo Credit: Wikipedia
The number of birds reported to have died there since the bird flu outbreak began varies greatly. The Chinese researchers whose studies were published today say 1,500 birds were dead by 20 May.
The following day, the Chinese Ministry of Agriculture filed a report to the World Organisation for Animal Health that 519 birds had been found dead.
Early in June, however, the recombinomics.com website said that 8,000 birds had died.The virus has killed 54 people in Cambodia, Vietnam and Thailand. In June, the Chinese government denied reports that 200 people had died of bird flu in the Qinghai province (see China denies human deaths from bird flu).
Link to full paper in Nature
Link to full article in Science
Nature 436, 191 (2005)
Science 309, 1206 (2005)