title: Limited evolution of West Nile virus has occurred during its southwesterly spread in the United States.
abstract: Analysis of partial nucleotide sequences of nine West Nile virus strains isolated in southeast Texas during June-August 2002 revealed a maximum of 0.35% nucleotide variation from a New York 1999 strain. Two sequence subtypes were identified that differed from each other by approximately 0.5%, suggesting multiple introductions of virus to this area. Analysis of sequences from cloned PCR products for one strain revealed up to 0.6% divergence from the consensus sequence at the subpopulation level. The presence of unique patterns of small numbers of mutations in North American West Nile strains studied to date may suggest the absence of a strong selective pressure to drive the emergence of dominant variants.
authors.affiliation: WHO Collaborating Center for Tropical Diseases, Galveston, TX 77555-0609, USA.
authors.forename: David W C
authors.initials: DW
authors.lastname: Beasley
authors.forename: C Todd
authors.initials: CT
authors.lastname: Davis
authors.forename: Hilda
authors.initials: H
authors.lastname: Guzman
authors.forename: Dana L
authors.initials: DL
authors.lastname: Vanlandingham
authors.forename: Amelia P A
authors.initials: AP
authors.lastname: Travassos da Rosa
authors.forename: Ray E
authors.initials: RE
authors.lastname: Parsons
authors.forename: Stephen
authors.initials: S
authors.lastname: Higgs
authors.forename: Robert B
authors.initials: RB
authors.lastname: Tesh
authors.forename: Alan D T
authors.initials: AD
authors.lastname: Barrett
mesh_terms: D000818:Animals; D001715:Bird Diseases / Q000453:epidemiology / Q000635:transmission* / Q000821:virology; D001717:Birds / Q000821:virology; D009033:Culicidae / Q000821:virology*; D019143:Evolution, Molecular; D005260:Female; D051379:Mice; D008969:Molecular Sequence Data; D020304:Raptors / Q000821:virology; D017422:Sequence Analysis, DNA; D020308:Songbirds / Q000821:virology; D013781:Texas / Q000453:epidemiology; D014774:Virulence; D014901:West Nile Fever / Q000453:epidemiology / Q000635:transmission* / Q000821:virology; D014902:West Nile virus / Q000235:genetics* / Q000472:pathogenicity