Figure 2. Identification of West Nile virus (WNV) in Puerto Rico. WNV premembrane-envelope maximum likelihood phylogenetic tree of WNV isolates collected from 1998 through 2007, demonstrating the relationship of viruses from Puerto Rico to other lineage I isolates. Viruses are labeled by place and year of isolation and GenBank accession no. FJ799714–FJ799717 (Fiji). Clade names are consistent with those used by Davis et al. (14). Numbers indicate the neighbor-joining bootstrap values for groups in the tree and are shown when >70. Scale bar indicates nucleotide substitutions per site.
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