September 07, 2006

As of noon today, eight additional human cases of West Nile virus have been identified in Manitoba during the week ending Sept. 6. This brings the total number of Manitobans who have tested positive for West Nile virus this year to 40.

Of the 40 Manitobans who have tested positive this year, 11 have been classified as cases of West Nile neurological syndrome, 12 have been classified as cases of West Nile non-neurological syndrome and one has been classified as asymptomatic or showing no symptoms. The rest are currently under investigation to determine if they meet the criteria for cases of West Nile virus.

Additional information on these cases, including age, gender, regional health authority of residence and likeliest area of exposure, will be provided on the website when it becomes available at http://www.gov.mb.ca/health/wnv.

Mosquito surveillance information from last week and preliminary information from this week indicates the number of biting Culex tarsalis mosquitoes has significantly decreased and the peak risk period for West Nile virus has passed. Most mosquitoes that are still actively biting are other types of mosquitoes which usually do not carry West Nile virus.

However, with the warm weather, some infected Culex tarsalis or other species may still be actively biting. For this reason, there will be a small, continued risk of West Nile virus infection through the early fall.

Therefore, to reduce the risk of West Nile virus, Manitobans are still advised to take personal protective precautions when mosquitoes are active. As daytime and evening temperatures become cooler, Culex tarsalis mosquitoes may become more active during the day and early evening as well as between dusk and dawn.

Manitobans can reduce the risk of mosquito bites by:

• reducing the amount of time spent outdoors during peak mosquito hours;

• using appropriate mosquito repellent;

• wearing light-coloured, loose-fitting clothing; and

• making sure doors and window screens fit tightly and are free of holes.

This year, positive mosquito samples have been found in 21 Manitoba communities: Steinbach, Carman, Selkirk, Boissevain, Carberry, Portage la Prairie, Gimli, Niverville, St. Andrews, Beausejour, Headingley, West St. Paul, Winnipeg, Brandon, Deloraine, East St. Paul, Stony Mountain, Oakbank, Sioux Valley First Nation, Winkler and Altona. The risk of West Nile virus, however, exists throughout all of southern Manitoba and is not limited to the communities listed. The West Nile virus has been identified in this or previous years within the boundaries of all regional health authorities except for NOR-MAN, Burntwood and Churchill.

Routine trapping for adult mosquitoes will end this week in some of the more remote trapping communities. As weather conditions are favourable, monitoring of adult mosquitoes will continue in most communities in southern Manitoba.

Weekly average trap counts of Culex tarsalis by regional health authority are available on the province’s West Nile virus website at http://www.gov.mb.ca/health/wnv.

For more information, visit the website or call Health Links–Info Santé at 1‑888‑315‑9257 or 788-8200 in Winnipeg.

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