Research report: Influenza A Viruses: Genome Sequences 27 October 2006

Long Intervals of Stasis Punctuated by Bursts of Positive Selection in the Seasonal Evolution of Influenza A Virus," is the title of a study published in the online journal Biology Direct on 26 Oct 2006, by Y Wolf et al, researchers from the National Library of Medicine's National Center for Biotechnology Information (NCBI) and the Fogarty International Center, both part of the National Institutes of Health. The findings substantially alter the existing understanding of how the influenza virus evolves, and could have important implications for monitoring changes to the virus and predicting which strains should be used for flu vaccine.

The researchers analyzed the genomic sequences of a large and representative collection of the 2 most common flu strains (called H3N2 and H1N1) from the 1995-2005 flu seasons in New York State and New Zealand. The sequence data were obtained from the Genome Sequencing Project, which recently generated over 1000 fully sequenced influenza genomes from clinical isolates; the project is funded and managed by the National Institute of Allergy and Infectious Diseases. The analysis revealed a picture of flu evolution that was surprisingly different from the prevailing conception of how the virus changes. Based on their results, the researchers conclude that, "the common view of the evolution of influenza virus as a rapid, positive selection-driven process is, at best, incomplete." Because the periods of stasis allow the proliferation of many small groups of related viruses, any of which could become the next dominant virus strain, the authors suggest that sequencing much larger numbers of representative isolates could be helpful in augmenting current surveillance methods.

http://www.sciencedaily.com/releases/2006/10/061026185115.htm