June 13, 2011 Scientists using new mathematical and
computational techniques have identified six influenza A viruses
that have particularly close genetic relationships to the H1N1
"swine" flu virus that swept through the United States beginning
in the spring of 2009. That virus eventually killed almost
18,000 people worldwide. Biological studies focused on these
strains of influenza virus could shed light on how the 2009
pandemic strain of influenza emerged, aiding in efforts to
forestall another pandemic, the researchers say. Five of these
viruses were isolated from pigs, and the sixth had infected a
human who worked with hogs. The researchers arrived at these
strains by using powerful computers to analyze the relationships
between the genomes of more than 5,000 strains of influenza A
that have been isolated over several decades and recently
sequenced. Rather than using the conventional approach of
constructing phylogenetic trees that illustrate organisms'
hypothetical ancestors, these scientists set up a ne