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 21, 2026

Surveillance data from week 32 showed high numbers of Culex tarsalis mosquitoes and evidence of a high rate of infection with West Nile virus (WNV) in the RM of West St. Paul. One additional round of fogging with DeltaGard 20EW is required under the existing ministerial order issued to the RM of West St. Paul, to reduce the risk of exposure to West Nile virus. Fogging is scheduled to be completed this weekend, weather dependent. The confirmed date will be communicated through the RM of West St. Paul.

One probable human WNV case from the Southern Health/Santé Sud region was reported this week. To date, four human WNV cases have been reported (1 confirmed, 3 probable).

Adult mosquito surveillance during the week of August 9 to 15, 2026 (week 32) detected C. tarsalis mosquitoes in all 21 trapping communities in Manitoba. The average number of C. tarsalis per trap decreased in all health regions compared to the previous week. The provincial average remained slightly higher than the historical average for week 32. More details are available at: https://www.gov.mb.ca/health/wnv/stats.html.

60 West Nile virus (WNV)-positive C. tarsalis mosquito pools were detected in Week 32 including in Prairie Mountain Health (Brandon and Boissevain), Interlake-Eastern Health (Beausejour, Oakbank, Selkirk and Stonewall), Southern Health/Santé Sud (Altona, Carman, Morris, Niverville, Portage la Prairie, and Winkler) and Winnipeg Health regions (Winnipeg, East St. Paul and West St. Paul). One WNV-positive horse was reported. To date, 333 WNV-positive C. tarsalis pools, 22 WNV-positive birds, and one WNV-positive horses have been identified.

As of August 20, the risk of human exposure to WNV in Manitoba is high. July and August are historically the months with the highest risk of WNV. Culex tarsalis activity is decreasing. However, with the continued detection of WNV infection in mosquitoes, Manitobans are still encouraged to take precautions to minimize their risk of mosquito bites while enjoying outdoor activities over the next few weeks. This includes:

  • 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.