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Phylogenetic trees were constructed from 119 viruses, including 55 HA1 (A) and NA (B) gene sequences of viruses sampled globally from October 2007 through April 2008 and showed that the genotype D remained dominant in circulation in the 2007–2008 influenza season. Trees were generated and labeled as in Figure 1, and strain designations of the 2007–2008 viruses were colored in olive for distinction.
