Northern virus genetics scarce

A brief report in The Scientist says that CDC researchers will publish findings on genetic changes in H5N1's HA binding site within weeks.

But the new 2005 gene sequences are taken from only a handful of isolates. WHO says scientists have had technical problems in trying to derive isolates from the hundreds of serum samples collected in over the past few months in Vietnam.

"CDC has only one isolate and sequence for H5N1 from North Vietnam cases reported in 2005," said Ruben O'Donis CDC's Chief of the Molecular Genetics Section Influenza Branch in an email to The Scientist.

This is consistent with other information that there have been unexpected difficulties in isolating and growing H5N1 virus from the north of Vietnam. It is not clear what the reason is for this.

The genetic sequence data is important information in assessing the likelihood of a genetic shift that might be evidence of pandemic potential. But it is only one kind of information. It is also unfortunately just as likely we will know a pandemic is underway when we start seeing obvious human-to-human spread in many areas in a short span of time.