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July 19, 2007 WEST NILE VIRUS UPDATE #5The Office of the Chief Medical Officer of Health advises that since last week, eight additional positive human test results for West Nile virus have been reported in Manitoba.
To date, a total of 14 positive test results for West Nile virus have been reported in Manitoba. Twelve test results were identified through clinical testing. Two test results were identified through Canadian Blood Services routine screening and the donated blood units were discarded according to plan.
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.
The numbers of Culex tarsalis mosquitoes identified in southern Manitoba for the week of July 8 remain higher than usual for this time of year. The last few weeks of July and the first few weeks of August are usually the peak risk period for human exposure to West Nile virus in Manitoba.
Surveillance data indicate the virus is present in Culex tarsalis mosquitoes throughout southern Manitoba at this time. The number of cases of the more severe type of West Nile virus (neurologic illness) in previous years has ranged from one to 35 cases per summer.
At this time of the season, the chief medical officer of health encourages Manitobans to reduce the risk of mosquito bites by:
· reducing the amount of time spent outdoors during peak mosquito hours between dusk and dawn;
· 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.
Manitobans are advised to reduce mosquito numbers near their homes and in their communities by reducing standing water. To reduce the development of Culex tarsalis mosquitoes:
· clean eavestroughs;
· at least once a week, empty bird baths and other items that might collect water;
· cover rain barrels with mosquito screening or maintain tight seals around downspouts; and
· dispose of old tires or other debris that collect water.
Adult mosquito control based on orders previously issued continues this week in Deloraine, Killarney and Winkler. The need for adult mosquito control under orders issued previously in Altona, Beausejour, Boissevain, Brandon, Carman, Deloraine, Headingley, Killarney, Morden, Niverville, Oakbank, Stonewall, West St. Paul, Winkler and Winnipeg is under continuous evaluation.
Mosquito samples from 11 other communities across southern Manitoba from the week of July 8 were identified as positive for West Nile virus. These communities are Carberry, Dauphin, Morris, Roblin, Russell, Sandy Bay First Nation, Selkirk, Sioux Valley First Nation, Steinbach, Virden and Winnipeg Beach. Adult mosquito control has not been recommended in these communities at this time.
To date in 2007, West Nile virus infected mosquitoes have been found in the communities of Altona, Beausejour, Boissevain, Brandon, Carberry, Carman, Dauphin, Deloraine, Headingley, Killarney, Morden, Morris, Niverville, Oakbank, Roblin, Russell, Sandy Bay, Sioux Valley, Souris, St. Andrews, Selkirk, Steinbach, Stonewall, Stony Mountain, Virden, West St. Paul, Winkler, Winnipeg and Winnipeg Beach. The province continues to monitor adult Culex tarsalis mosquito numbers in these communities and others across southern Manitoba.
Health Canada has concluded the use of malathion for adult mosquito control in residential areas using ultra-low-volume application will not pose a health concern. However, people who wish to further reduce their exposure to malathion can take additional precautions including:
· closing all doors and windows,
· avoiding trucks while spraying is underway,
· turning off fans and air conditioners or setting them at exhaust,
· removing clothes and children’s toys from outdoor areas,
· rinsing any household items or toys left outside before using them, and
· washing fruits and vegetables.
Information on adult mosquito control schedules for West Nile virus and weekly average trap counts of Culex tarsalis by regional health authority is available on the province’s West Nile virus website at http://www.gov.mb.ca/health/wnv. Updated information on the risk of West Nile virus will be provided to the public throughout the summer. Manitobans can check the West Nile virus website regularly for up-to-date data and information.
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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