Genetic Variability of West Nile Virus in US Blood Donors, 2002–2005
Figure 2. Distance analysis of envelope glycoprotein of West Nile virus isolates collected during 1999–2006 epidemics in the United States. Phylogram is based on maximum parsimony analysis of complete nucleotide sequences of the envelope gene. Diamonds indicate isolates from this study. All isolates from clade 2 (WN02 strain) contained conserved mutations at positions 1442 (T → C) and 2466 (C → T). Values near branches represent percentage support by parsimony bootstrap analysis. Scale bar represents a 1-nt change.