title: West Nile virus range expansion into British Columbia.
abstract: In 2009, an expansion of West Nile virus (WNV) into the Canadian province of British Columbia was detected. Two locally acquired cases of infection in humans and 3 cases of infection in horses were detected by ELISA and plaque-reduction neutralization tests. Ten positive mosquito pools were detected by reverse transcription PCR. Most WNV activity in British Columbia in 2009 occurred in the hot and dry southern Okanagan Valley. Virus establishment and amplification in this region was likely facilitated by above average nightly temperatures and a rapid accumulation of degree-days in late summer. Estimated exposure dates for humans and initial detection of WNV-positive mosquitoes occurred concurrently with a late summer increase in Culex tarsalis mosquitoes (which spread western equine encephalitis) in the southern Okanagan Valley. The conditions present during this range expansion suggest that temperature and Cx. tarsalis mosquito abundance may be limiting factors for WNV transmission in this portion of the Pacific Northwest.
authors.affiliation: British Columbia Centre for Disease Control, Vancouver, British Columbia, Canada. david.roth@bccdc.ca
authors.forename: David
authors.initials: D
authors.lastname: Roth
authors.forename: Bonnie
authors.initials: B
authors.lastname: Henry
authors.forename: Sunny
authors.initials: S
authors.lastname: Mak
authors.forename: Mieke
authors.initials: M
authors.lastname: Fraser
authors.forename: Marsha
authors.initials: M
authors.lastname: Taylor
authors.forename: Min
authors.initials: M
authors.lastname: Li
authors.forename: Ken
authors.initials: K
authors.lastname: Cooper
authors.forename: Allen
authors.initials: A
authors.lastname: Furnell
authors.forename: Quantine
authors.initials: Q
authors.lastname: Wong
authors.forename: Muhammad
authors.initials: M
authors.lastname: Morshed
mesh_terms: D000818:Animals; D001955:British Columbia / Q000453:epidemiology; D002980:Climate; D003465:Culex / Q000821:virology*; D006734:Horse Diseases / Q000453:epidemiology / Q000821:virology; D006736:Horses; D006801:Humans; D007303:Insect Vectors / Q000821:virology*; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D014901:West Nile Fever / Q000453:epidemiology* / Q000635:transmission / Q000821:virology*; D014902:West Nile virus / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D012367:RNA, Viral