Emerg Infect DiseidEmerging Infectious Diseases1080-60401080-6059Centers for Disease Control115855272631742Research ArticlePartial genetic characterization of West Nile virus strains, New York State, 2000.EbelG. D.ebel@wadsworth.orgDupuisA. P.2ndNgoK.NicholasD.KauffmanE.JonesS. A.YoungD.MaffeiJ.ShiP. Y.BernardK.KramerL. D.Arbovirus Laboratories, New York State Department of Health, 5668 State Farm Road, Slingerlands, NY 12159, USA.Jul-Aug200174650653

We analyzed nucleotide sequences from the envelope gene of 11 West Nile (WN) virus strains collected in New York State during the 2000 transmission season to determine whether they differed genetically from each other and from the initial strain isolated in 1999. The complete envelope genes of these strains were amplified by reverse transcription-polymerase chain reaction. The resulting sequences were aligned, the genetic distances were computed, and a phylogenetic tree was constructed. Ten (0.7%) of 1,503 positions in the envelope gene were polymorphic in one or more sequences. The genetic distances were 0.003 or less. WN virus strains circulating in 2000 were homogeneous with respect to one another and to a strain isolated in 1999.