TOKYO--The H5N1 avian influenza virus, which has caused the deaths of 54 people and over 140 million fowl, continues to expand its range in China. Samples recently recovered from China's western Qinghai Province show the virus there has been matched genetically to that found on the southeast coast, researchers say, reigniting a debate over whether it is being spread by migratory birds or human activities. The World Health Organization has warned that if the virus acquires the ability to pass easily between humans, it could start a global pandemic.
On 8 June, China's Ministry of Agriculture reported that the
H5N1 virus had been found in the Xinjiang Uygur Autonomous Region,
the westernmost confirmed sighting so far. This announcement came
after mid-May reports that H5N1 caused the deaths of over 1,000
migratory birds in the Qinghai Lake region of Qinghai Province,
which borders Xinjiang to the east. The country's National Avian
Influenza Reference Laboratory, Harbin Veterinary Research
Institute, recently completed sequencing an isolate from the
Qinghai outbreak. Lab director Chen Huanlan says it is "not a new
viral genotype" but similar to the viral strains found in southeast
China last year [ScienceNOW
7 July, 2004:]. Guan Yi, a virologist at the University of Hong
Kong, says the finding raises questions about "how the virus got
there."One theory holds that human activity--moving live chickens
or infected crates or vehicles--carries the virus, even over long
distances. But Chinese authorities blame migratory birds. Chu
Guozhong, an ornithologist at the State Forestry Administration,
Beijing, says there are no farms in the Qinghai Lake area where the
migrants could have come in contact with domestic poultry. But he
acknowledges that migratory birds, which breed in Qinghai, fly
southwest for the winter to India and Bangladesh, not to southeast
China where H5N1 is now believed to be endemic. He suspects the
birds picked up the virus en route or have been carrying it for
some time. Waterfowl typically carry the virus with minimal
symptoms. But Chu says unusually cold weather and a late snowfall
made foraging difficult and left the birds weakened and less
resistant to viral infections. David Melville, a New Zealand-based
ornithologist not affiliated with any research institute who
studies migratory bird routes in Asia, says there is now a real
possibility that these birds could carry the virus to their
wintering grounds in India and Bangladesh, where there are no
confirmed findings of H5N1. Related site:
WHO fact sheet
on Avian flu
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