WASHINGTON, Nov. 2 (UPI) -- U.S. researchers are reporting
results of a study that substantially alters the existing
understanding of how influenza viruses evolve. The findings by
National Institutes of Health scientists are said to have
important implications for monitoring changes to such viruses
and predicting which strains should be used for flu vaccine. In
an effort to better understand how seasonal influenza evolves
into new strains, the researchers analyzed the genomic sequences
of the two most common flu strains -- H3N2 and H1N1 -- from the
1995-2005 flu seasons in New York state and New Zealand. The
sequence data was obtained from the Genome Sequencing Project,
which recently generated more than 1,000 fully sequenced
influenza genomes from clinical isolates. The analysis reveals a
picture of flu evolution that is surprisingly different from the
prevailing conception of how the viruses change. For example,
evolution of the influenza A virus is commonly viewed as a
typical Darwinian process. Unexpected