Fig. 3: midpoint phylogenetic tree of nucleotide sequences using only polyprotein coding region of 1582 West Nile virus (WNV) strains representing different viral lineages. The analysis of those nucleotide sequences was performed using the maximum likelihood method based on the GTR matrix-based model. Different phylogenetic groups are assigned to previously defined lineages; highlighted in dark blue, strains included in lineage 1a from USA and in light blue strains included in lineage 1a from Europe, Asia and Africa. Strains from Brazil (red), Mexico (orange), Colombia (purple), and Argentina (green) were also identifies on the phylogenetic tree. Numbers over each main node of the tree correspond to bootstrap values (1000 replicates). Values < 70 are not supported by reproducible topologies. The bar represents nucleotide substitutions along of the branch.