West Nile Virus Surveillance 2011

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Saskatoon Health Region Map

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West Nile Virus (WNv) Risk Summary to September 2, 2011

The risk of WNv transmission in SHR is low.

Personal protective measures are recommended.

For detailed provincial risk map see http://www.health.gov.sk.ca/west-nile-risk

Saskatoon Health Region
There have been no human cases to date and no positive mosquito pools. One WNv positive bird was identified in Saskatoon in previous weeks. All indicators suggest the transmission risk of WNv is low. The average number of Culex tarsalis (the species that can transmit WNv to humans) that have been caught in traps have decreased to 2.6 for the week Aug 19-26, compared to 4.5 from the previous week. These numbers are about the same as last year.

Saskatchewan
Three positive mosquito pools have been identified in the southern part of the province. No human cases have been reported to date in the province. Culex tarsalis numbers are starting to decline in most communities however counts remained high in Assiniboia (292.3/night), Estevan (139.0/night), and Swift Current (43.0/night). Numbers naturally decline at this time of the year.

The risk for West Nile remains relatively low this year, it is not a zero risk. People should still be using personal protective measures particularly as dusk approaches in those areas that have had high numbers of Culex tarsalis recently.

Western Canada and Northwest USA
There have been no human cases in Manitoba or Alberta. There have been three (3) human cases reported from North Dakota and one (1) from South Dakota. Ontario is reporting four (4) human cases including one (1) travel-related human case and 200 positive mosquito pools. There have been four (4) positive mosquito pools from Quebec. The Centers for Disease Control (CDC) in the US is reporting 104 human cases and four (4) deaths (to Aug. 30, 2011).

1. Centres For Disease Control USA (CDC) traps are traps used to attract and capture live mosquitoes (using carbon dioxide) for testing for the virus. 

2. Two Culex tarsalis mosquitoes have been found in New Jersey traps (killed mosquitoes that cannot be tested for the virus) in the city of Saskatoon. The presence of C tarsalis species does not necessarily mean that the virus is circulating unless positive pools are indicated.

Centres For Disease Control USA (CDC) West Nile Virus www.cdc.gov/ncidod/dvbid/westnile/index.htm

For updated risk levels throughout the province see the Government of Saskatchewan West Nile Virus Risk Levels page:

www.health.gov.sk.ca/west-nile-risk

Other WNv Surveillance Websites

• City of Saskatoon Surveillance (by location)

• Saskatoon Mosquito Control

• Saskatchewan Ministry of Health (surveillance)

• Public Health Agency of Canada (WNv Monitor)

• Centres For Disease Control USA (CDC) (West Nile Virus)