That's good news when it comes to the notorious Asian bird flu that scientists are watching anxiously today. That strain, known as H5N1, bears hemagglutinin — the H in its name — that still prefers cells mostly found in the gastrointestinal tracts of birds.
While it has killed at least 164 people worldwide and killed or prompted the slaughter of millions of birds across Asia since late 2003, the H5N1 virus can't yet spread easily from person to person.
"This is very, very elegant work," said Dr. William Schaffner, an infectious disease specialist at Vanderbilt University who advises the federal government on flu issues.
"It may not be exactly the same mutations that would change an H5 virus," Schaffner cautioned. Still, he said, "We appear to be narrowing down our understanding of the kinds of mutations it might take to change a bird-specific virus to one that could be transmitted readily among humans."
The CDC's next step, in fact, is to study these same changes in hemagglutinin amino acids, the protein's building blocks, in H5N1.
But it will almost certainly take additional genetic changes to turn the H5N1 bird flu into a major human killer, changes that probably involve other proteins than just hemagglutinin, contends lead researcher Dr. Terrence Tumpey, a CDC microbiologist.
"I think that researchers may discover that the combination of genes needed is maybe unlikely to occur in nature," he said.
