Phylogenetic tree of nucleotide sequence alignment of WNVs, including the human isolate Beaumont strain. Nucleotide sequences are full-length genomes, approximately 11,000 nucleotides. The phylogram was constructed by using maximum parsimony and heuristic methods, with bootstrap values shown at nodes. The following full-length genome sequences were obtained from GenBank for comparison, with accession numbers in parentheses: Egypt 1951 human (Eg 101) (AF260968), Italy 1998-equine (AF404757), Volgograd 1999 human brain isolate (AF317203), Volgograd 1999 human brain isolate (AY277252), Volgograd 2000 human blood isolate (AY278442), Caucasus 1998 mosquito isolate (AY277251), Astrakhan 1999 human isolate (AY278441), Israel 1998-Stork (AF481864), Uganda 1937 human isolate (M12294), Kunjin (D00246), CN 1999-MQ 2741 (AF206518), RO97-50 mosquito isolate from Romania (AF260969), New York 382-99 Flamingo isolate (AF196835), New York human isolate 2001 (AF533540), Maryland 2000-Crow 265 (AF404753), New York 2000-Crow 3356 (AF404756), New York 2000-Grouse 3282 (AF404755), New York 1999-equine (AF260967), New York human isolate 1999 (AF202541), New Jersey 2000-MQ5488 mosquito isolate (AF404754), and Kenya 1998 mosquito isolate (AY262283).