WEDNESDAY, Feb. 27 (HealthDay News) -- Several strains of H5N1bird flu virus that afflicted southern China were blocked from enteringneighboring Thailand and Vietnam, say University of California, Irvine,researchers who conducted the first-ever statistical analysis of H5N1´sgenetic diversity.

The information gleaned from this analysis may help scientists betterunderstand how the strain migrates and, in future, determine the successof programs to halt the spread of the virus. The study was publishedonline Feb. 27 in the journal PLoS One.

"Some countries appear more exposed to bird flu invasion than others.Learning that is a good step in discovering which social and ecologicalfactors promote, or, on the other hand, hamper the virus´ spread," leadauthor Robert G. Wallace, a postdoctoral researcher, said in a preparedstatement.

He and colleague Walter M. Fitch, professor of ecology and evolutionarybiology, analyzed almost 500 publicly available genetic sequences ofproteins found on the surface of H5N1 samples collected from 28 locationsin Africa, Asia and Europe.

They found that H5N1 strains in Indonesia, Japan, Thailand and Vietnamshared the most evolutionary history with H5N1 found in three southernChinese provinces -- Guangdong, Fujian and Hong Kong -- that are engagedin intensive international trade, including poultry.

Previous research has identified poultry trade as the key factor in thespread of H5N1.

The type of genetic analysis used in this study could help healthofficials in different countries determine whether their efforts tocontrol H5N1 are effective, the UCI researchers said.

"You can think of it as a type of evolutionary forensics," Wallacesaid. "When a bomb explodes, investigators can determine how many chargeswent off and the strength and direction of the blast, all from theresulting damage alone. Here we can determine the way H5N1 has spread andevolved by the resulting viral diversity."

More information

The World Health Organization has more about bird flu.