West Nile virus range expansion into British Columbia.
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.
Roth
David
D
British Columbia Centre for Disease Control, Vancouver, British Columbia, Canada. david.roth@bccdc.ca
Henry
Bonnie
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Mak
Sunny
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Fraser
Mieke
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Taylor
Marsha
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Li
Min
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Cooper
Ken
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Furnell
Allen
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Wong
Quantine
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Morshed
Muhammad
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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*
D012367:RNA, Viral