Weekly West Nile Virus Update
The WNV Story Map may not always be updated at the same time as the WNV Surveillance Statistics website and the Weekly Update. Please check back later if the Story Map does not align with the Weekly Surveillance Statistics and Weekly Update.
August 15, 2025
On August 7, 2025, the Manitoba government issued a ministerial order under the Environment Act to spray for adult mosquitoes because of high numbers of adult Culex tarsalis mosquitoes and evidence of a high rate of mosquito infection with West Nile virus (WNV) in the City of Winkler. Two rounds of treatment were completed on August 8/9 and August 12/13, 2025.
Adult mosquito control schedules and maps are available at: www.gov.mb.ca/health/wnv/control.html.
Adult mosquito surveillance conducted during the week of August 3 to August 9, 2025 (week 32) detected Culex tarsalis mosquitoes in 21 of 21 trapping communities in Manitoba. Numbers were increased from the previous week but for the province, are average for week 32. Numbers were highest in Southern Health region.
48 West Nile virus (WNV) positive Culex tarsalis mosquito pools were detected in Week 32 including positives in Altona, Boissevain, Killarney, Morden, Morris, Oakbank, Steinbach, Winkler and Winnipeg. To date, 105 WNV-positive Culex tarsalis pools, three WNV-positive birds and zero WNV-positive horses have been identified. One confirmed WNV human case was reported, related to travel outside of Canada.
Recent rainfall and warm temperatures are supporting Culex tarsalis development. The risk of WNV exposure is high and may increase further in August. July and August are historically the months with the highest risk of WNV.
Manitobans are encouraged to enjoy outdoor activities and reduce the risk of mosquito bites and exposure to WNV 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 with long sleeves and pant legs, and
- maintaining door and window screens so they fit tightly and are free of holes.
Manitobans can also reduce the number of mosquitoes around their home by eliminating standing water. To reduce standing water:
- clean eaves troughs 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.
