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