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September 6, 2007 WEST NILE VIRUS UPDATE #12The Office of the Chief Medical Officer of Health advises it is investigating a human death that may be related to a West Nile virus infection.
The investigation is underway to confirm a West Nile virus infection and the role West Nile virus may have played in the death of a man in his 60s, who was a resident of the Interlake health region. If confirmed, this will be the third human death related to a West Nile virus infection in Manitoba in 2007.
As of end of day Wednesday, 90 additional positive human test results for West Nile virus have been reported in Manitoba since last week. These new results mostly reflect exposures to infected mosquitoes before mid-August.
To date, a total of 445 individuals have tested positive for West Nile virus (WNV) this year in Manitoba. Of these, 20 test results were identified by Canadian Blood Services routine screening. The donated blood units were discarded as planned.
Even though mosquito activity may appear to be low, the risk of exposure to West Nile virus this summer has not yet ended. The importance of taking personal protective precautions against mosquitoes continues. Ongoing mosquito surveillance indicates that current numbers of active West Nile virus-infected mosquitoes are decreasing. However, infected mosquitoes continue to be present in most parts of southern Manitoba.
As daytime and evening temperatures become cooler, Culex tarsalis mosquitoes may become more active in the afternoon and early evening. Manitobans are encouraged to reduce the risk of mosquito bites by:
· reducing the amount of time spent outdoors in the afternoon and early evening when mosquitoes are now more active, and whenever mosquito activity is observed;
· using appropriate mosquito repellent;
· wearing light-coloured, loose-fitting clothing; and
· maintaining door and window screens so they fit tightly and are free of holes.
No new orders under Manitoba’s Environment Act are being issued to control adult mosquitoes at this time. Adult mosquito control based on orders previously issued is not indicated at this time.
The number of cases of the more severe type of West Nile virus (i.e. WNV neurological syndrome) in previous years has ranged from one to 35 cases per summer. The total number of cases of all types of West Nile virus in previous years has ranged from three to 143. To date in 2007, 139 WNV human cases have been classified of which 32 are WNV neurological syndrome.
Additional information on human cases including age, gender, regional health authority of residence and likeliest area of exposure, as well as information on adult mosquito control schedules will be provided on the website as it becomes available at http://www.gov.mb.ca/health/wnv.
Information on weekly average trap counts of Culex tarsalis by regional health authority and a list of communities where infected mosquitoes have been found is available on the province’s West Nile virus website at http://www.gov.mb.ca/health/wnv. Manitobans can check the West Nile virus website regularly for up-to-date data and information throughout the summer.
More information about West Nile virus is also available from Health Links–Info Santé at 788-8200 or 1‑888‑315-9257.
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