Epidemiology of West Nile Virus (WNV) in Canadians
5 WNV lineages identified based on genomic phylogeny
Canada represents the northernmost range of WNV in North America
2001: First positive WNV indicator in Canada, virus was detected in birds and mosquitoes in Ontario
2002: 394 human cases in Ontario and 20 human cases in Quebec
2003: WNV spread quickly to the prairie provinces with a proportion of the cases resulting in West Nile Neurologic Syndrome (WNNS) that occured mostly in the southern parts of Canada.
- Lineage 1: dominates, viruses detected throughout Africa, Asia and since 1999, the Americas, and recently
- Lineage 2: originally thought to be restricted to sub-Saharan Africa, can also be found in Austria, Greece, Hungary, Italy and Russia
- Lineage 3: detected in Czech Rupublic
- Lineage 4: detected in Russia
- Lineage 5: detected in India
2007: 2nd major outbreak in Canada! 1456(113 WNNS) cases in Saskatchewan, 587(72 WNNS) cases in Manitoba, and 318(21 WNNS) cases in Albera
2009: Long-delayed range expansion of WNV into British Columbia. 2 cases in humans, 10 positive mosquito pools and 3 cases in horses detected by provincial surveillance
- 947(63 WNNS) cases in Saskatchwan, 144(35 WNNS) cases in Manitoba and 275(48 WNNS) cases in Alberta
- Delayed establishment of WNV in BC may be due to:
- limited or failed introduction of virus from adjacent areas
- previously unsuitable enviornmental or ecologic conditions that prevented establishment, persistence and amplification of WNV to detectable levels
- It is hypothesized that Washington state in 2009 provided a sufficient source of WNV, and with higher than normal nightly temperatures and elevated numbers of mosquitoes in the southern Okanagan Valley, the conditions facilitated the establishment of WNV in BC.
Engler, O., et al. (2013) European Surveillance for West Nile Virus in Mosquito Populations. Int. J. Environ. Res. Public Health. 10:4869-95.
Roth, D. et al.(2010) West Nile Virus Range Expansion into British Columbia. Emerg Infect Dis. 16(8):1251-8.