H5N1 source: China, gene study suggests

from WorldPoultry.net
March 24, 2008

Researchers have now suggested that southern China may have been the source for much of the spread of the H5N1 bird flu virus.

Reuters has reported that flu experst have found that a genetic analysis of the highly pathogenic H5N1 virus shows that strains that appeared in Vietnam, Thailand and Malaysia in 2002 and 2003 closely resemble a strain from poultry markets in China's Yunnan Province.

It was reported in the Journal of Virology that the two viruses found in poultry in China's Hunan province in 2002 and 2003 were most closely related to viruses from Indonesia.

"These results suggest a direct transmission link for H5N1 viruses between Yunnan and Vietnam and also between Hunan and Indonesia during 2002 and 2003," wrote the researchers*. "Poultry trade may be responsible for virus introduction to Vietnam, while the transmission route from Hunan to Indonesia remains unclear," they wrote.

The H5N1 bird flu virus was first seen in a goose in southern China's Guangdong province in 1996. The virus re-emerged in 2003. Since then, H5N1 bird flu has been found in more than 60 countries and territories. It has killed 236 people out of 373 infected in 14 countries -- Myanmar, Turkey, Djibouti, Azerbaijan, Egypt, Pakistan, Iraq, Indonesia, Thailand, Vietnam, China, Nigeria, Laos and Cambodia.

The team of researchers to find out if H5N1 viruses all descend from one type. "Due to the lack of influenza surveillance prior to these outbreaks, the genetic diversity and the transmission pathways of H5N1 viruses from this period remain undefined," they wrote.

In 2007, a team at the University of California Irvine reported that Guangdong appeared to be the source of renewed waves of the H5N1 strain, but Chinese officials denied the report at the time.

* Included Guan Yi of the University of Hong Kong and Robert Webster of St. Jude Children's Research Hospital in Memphis, Tennessee.