August 13, 2008
West Nile Virus Update #11
The Office of the Chief Medical Officer of Health advises that test results from Cadham Provincial Laboratory indicate the first human cases of West Nile virus from the 2008 season have been identified in Manitoba.
The first individual, a male in his 50s, is from the Winnipeg Regional Health Authority area. Further investigation is underway to confirm when and where exposure may have occurred and the severity of illness.
Further investigation is also underway on a reported human case for an individual who lives outside of Manitoba. Exposure for this case may have taken place in the Assiniboine or Brandon health region.
In 2007, 587 cases of West Nile virus were identified in Manitoba. Of those, 72 cases were identified as West Nile virus neurological syndrome, which is the most severe form of the disease, 501 cases were identified as the less severe West Nile virus non-neurological syndrome and nine cases showed no symptoms. The first human case last year was reported on June 21.
Culex tarsalis mosquito samples infected with West Nile virus have been identified from the communities of Brandon and Killarney for the first time this season, as well as additional infected samples from Boissevain, Deloraine and Selkirk. The samples were collected during the week of Aug. 3. Infected mosquitoes were previously identified in the communities of Boissevain, Deloraine, Selkirk, Sioux Valley, Stonewall, Virden and Winnipeg.
The numbers of trapped Culex tarsalis mosquitoes have increased in most southern Manitoban communities, with highest overall numbers in the Assiniboine health region.
With warm weather, it is anticipated that more infected mosquitoes may be identified in additional communities this season, with an ongoing risk of exposure to West Nile virus. In previous years, the peak risk period for human exposure to West Nile virus has been the last two weeks of July and the first three weeks of August.
No orders for adult mosquito control have been issued.
Manitobans are encouraged 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 can reduce mosquitoes around their home by reducing standing water. To prevent the development of Culex tarsalis mosquitoes, homeowners should:
· clean eavestroughs and regularly empty bird baths and other items that might collect water,
· ensure rain barrels are covered with mosquito screening or are tightly sealed around the downspout,
· clear yards of old tires or other items that collect water, and
· improve landscaping to prevent standing water around the home.
Weekly average trap counts of Culex tarsalis by regional health authority are available on the province’s West Nile virus website at www.gov.mb.ca/health/wnv.
Information on the risk of West Nile virus will continue to be provided to the public throughout the summer. Manitobans can also check the West Nile virus website regularly for up-to-date data and information.
For more information about West Nile virus, contact Health Links–Info Santé at 788-8200 or 1‑888‑315-9257 (toll-free) or visit the Manitoba Health website at www.gov.mb.ca/health/wnv.
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