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.

July 31, 2026

On July 30, the Manitoba government issued Ministerial Orders under The Environment Act to fog for adult mosquitoes after surveillance identified high numbers of adult Culex tarsalis mosquitoes and evidence of a high rate of West Nile virus (WNV) infection in mosquitoes in Carman, Stonewall, West St. Paul, Winkler and parts of Winnipeg.

High temperatures across southern Manitoba have shortened the time for infected C. tarsalis mosquitoes to develop and transmit the virus to humans. The province is currently in the highest risk period for human exposure, which is historically July 15 to August 15 each year.

Further details may be found in the news bulletin at: Province of Manitoba | News Releases | West Nile Virus Bulletin #1

Fogging details and schedule of the adult mosquito control and maps are available at: www.gov.mb.ca/health/wnv/control.html.

Adult mosquito surveillance conducted during the week of July 19 to July 25, 2026 (week 29) detected C. tarsalis mosquitoes in all 21 trapping communities in Manitoba. The number of mosquitoes per trap increased from the previous week and were significantly higher than the historical average for week 29.

73 West Nile virus (WNV)-positive C. tarsalis mosquito pools were detected in Week 29 including in Prairie Mountain Health (Boissevain-1 and Brandon-1), Interlake-Eastern Health (Beausejour-4; Selkirk-4 and Stonewall-11), Southern Health/Santé Sud (Altona-2; Carman-3; Morden-2; Ste. Anne-5 and Winkler-16) and Winnipeg Health regions (East St. Paul -1; Winnipeg-19 and West St. Paul-4). The very high C. tarsalis count in Carman and West St. Paul (>1200 per trap night) increased their risk rating. To date, 91 WNV-positive C. tarsalis pools, 8 WNV-positive birds and zero WNV-positive horses have been identified. No human cases have been confirmed in the province so far this year.

The risk of human exposure to WNV in southern Manitoba is high. Manitobans are strongly encouraged to reduce the risk of mosquito bites while enjoying outdoor activities 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.