for National Geographic News
A newly discovered bird flu strain has emerged in China and has spread rapidly through poultry in Southeast Asia.
Human infections by the new strain have also turned up in several locations, including both farms and urban centers, intensifying fears of a worldwide flu pandemic that could kill millions. (Related: "Bird Flu Will Reach U.S. and Canada This Fall, Experts Predict" [March 14, 2006].)
Magnifying those concerns is the vaccine-selective nature of the new strain, which means that existing animal vaccines are less effective on it than they are on previously known bird flu types.
"This virus seemed to spread very fast over a big geographic region," said Yi Guan, director of the State Key Laboratory of Emerging Infectious Diseases at the University of Hong Kong in China.
A team led by Guan discovered the new strain—dubbed "Fujian-like"—while monitoring chickens, ducks, and geese in Chinese markets, including several in Fujian Province (map of China).
"However, we don't have any evidence to show whether this virus is more dangerous or less dangerous than any other H5N1 [bird flu] viruses," Guan said.
He and his colleagues report their findings in this week's issue of the Proceedings of the National Academy of Sciences.
To help prevent the spread of bird flu, China has instituted an extensive, compulsory vaccination program for chickens.
But the effort has proven unable to contain the new strain, which has displaced other H5N1 variants to become the dominant strain in the southern China surveillance area, Guan says.
The new virus accounted for 95 percent of the infected birds that Guan's team examined between April and June 2006.
"This novel variant may have become dominant ... because it was not as easily affected as other strains by the avian vaccine used to prevent H5 infection," Guan said.
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