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.

September 5, 2025

Adult mosquito surveillance conducted during the week of August 24 to 30, 2025 (Week 35) detected a significant decrease in the number of Culex tarsalis mosquitoes in all health regions compared to the previous weeks. C. tarsalis mosquitoes were detected in 14 of 21 trapping communities in Manitoba. The Southern Health – Santé Sud region had the highest counts (1.39 Culex tarsalis / trap night).

No West Nile virus (WNV) positive C. tarsalis mosquito pools were detected in Week 35. To date, 147 WNV-positive C. tarsalis pools, 20 WNV-positive birds and zero WNV-positive horses have been identified. One confirmed WNV human case was reported, related to travel outside of Canada. While many people who get WNV will experience minor or no symptoms and not report their illness, serious illness can occur in all age groups, especially in older adults and persons with weakened immune systems.

Although numbers are low, Culex tarsalis may continue to bite on warm afternoons and evenings, and at dusk until the first hard frost. Manitobans are encouraged to take precautions to 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.