China is source of bird flu virus, study shows

WASHINGTON (Reuters) - China's southern Guangdong Province is the source of the dangerous H5N1 avian flu virus, according to a genetic analysis of the virus published on Monday.

And Guangdong appears to be the source of renewed waves of the H5N1 strain, which has killed or forced the destruction of hundreds of millions of birds, the team at the University of California Irvine reported.

"We show that the Chinese province of Guangdong is the source of multiple H5N1 strains spreading at both regional and international scales," the researchers wrote in their report, published in the Proceedings of the National Academy of Sciences.

"It is probably still originating there and spreading," Walter Fitch, a professor of ecology and evolutionary biology who worked on the study, said in a telephone interview.

"If you can control the virus at its source, you can control it more efficiently," Fitch added in a statement.

"With a road map of where the strain has migrated, you're more likely to isolate the strain that you should be using to make the vaccine."

Since 2003, H5N1 has spread to more than 50 countries as far away from China as Nigeria and Britain. The real fear is that the virus could mutate into a form that people can easily pass from one to another and spark a pandemic.

So far it has infected 277 people and killed 167 of them, according to the World Health Organization.

The researchers looked at samples of the virus taken from across China and as far west as Russia. They also looked at the genetic sequences of virus samples placed in GenBank, a public access database of genetic information.

Fitch's team constructed a "family tree" for the virus, which mutates quickly. They looked specifically at two proteins, called hemagglutinin and neuraminidase, the "H" and "N" in a flu strain's name.

'MULTIPLE OUTBREAKS'

They show the basic version of the virus is a form seen in Guangdong again and again.

"It seems to be seeding multiple outbreaks both from within China and elsewhere. That is the primary epicenter. Now there are secondary epicenters, as well, that have caught on fire," said Robert Wallace, a postdoctoral researcher who led the study.

The researchers' maps show China's northwest Qinghai Province to be another source of bird flu's spread.

The study has practical value, Wallace said in a telephone interview. For instance, neighboring countries can carefully watch imports from southern China and can make bird vaccines that match the Chinese strain of H5N1.

"Certainly the Chinese can investigate what is going on in Guangdong and if their (poultry) plants there contribute to those strains, they could so something to intervene," Wallace added.

In contrast to China, the researchers found that Indochina -- Thailand, Cambodia and Vietnam -- appeared to absorb strains of the virus. They said H5N1 spreads there but does not spread from there to anywhere else.

Both Fitch and Wallace said the study demonstrates why it is important for countries to share samples of the virus from within their borders with the scientific community.