A MASSIVE analysis of flu viruses has finally confirmed what everyone suspected: the H5N1 virus has been circulating in Chinese poultry for over a decade.
Yi Guan at Shantou University, China, and his colleagues studied samples from 13,000 migratory birds and 50,000 market poultry in south-east China between January 2004 and June 2005. They found H5N1 in around 2 per cent of apparently healthy ducks and geese, and also in some chickens.
Most importantly, the virus’s genes formed geographic clusters that differed slightly between the Chinese provinces of Guangdong, Hunan and Yunnan, suggesting that it must have been circulating long enough to have evolved into different strains.
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“They found H5N1 in around 2 per cent of ducks and geese, and also in some chickens”
The study, published in Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0511120103), pinpoints Guangdong and neighbouring Guangxi and Hunan provinces in south-eastern China as the probable source of the virus, as H5N1 there shows the most genetic variation. The virus then “colonised” other areas: viruses from Thailand and Vietnam are most similar to viruses from Guangdong, while Vietnam appears to have been repeatedly invaded by H5N1 from Guangxi province, most recently in 2005. In the past Chinese officials have insisted that H5N1 exists only in isolated cases in China, and did not necessarily originate there.
