Figure. Genetic relatedness of geographically distinct West Nile isolates determined by using the nucleotide sequence data from a 227-bp region of the E gene. The tree was constructed with PAUP (35) by using neighbor-joining distance program. Node values were determined from 500 replicates. Isolates are labeled: country of isolation-strain identification/year of isolation. GenBank accession numbers are provided in Table 1 and 2. (*AUS, Australia; **CAR, Central African Republic; ***SA, South Africa). Sequences derived from West Nile virus isolates determined in the Special Pathogens Unit are shown in bold, italic type.