Bird Flu Strain Diversified, May Be Harder to Conquer

Scientists may need to cast a much wider net to track and curb the spread of bird flu, a new study suggests.

That's because the deadly H5N1 avian influenza strain has several distinct genetic branches, or sublineages, spread across several geographic regions, the research shows.

Robert Webster, a virologist at St. Jude Children's Research Hospital in Memphis, Tennessee, and in the department of microbiology at the University of Hong Kong, co-authored the study.

He says the variations may pose a troubling puzzle for scientists hoping to develop effective, strain-specific human vaccines to battle a possible pandemic.

"The virus in Turkey is different from the one in Indonesia, which is different from the one in Vietnam, and so on," Webster said. "We have no idea which might be the one that takes off—if any of them do."