West Nile-infected mosquitoes detected for first time this summer in Manitoba

Provincial health authorities have detected mosquitoes infected with West Nile virus for the first time this summer, but no human cases have been reported.​

No human cases reported; threat insufficient for provincial fogging order

Culex tarsalis is the mosquito known to transmit West Nile virus to people. West Nile-infected mosquitoes have been detected for the first time this summer.

Provincial health authorities have detected mosquitoes infected with West Nile virus for the first time this summer, but no human cases have been reported.​

Mosquitoes carrying West Nile were found in adult-mosquito traps in Winnipeg and its eastern neighbour of Anola during the first week of July, Manitoba Health, Seniors and Active Living announced in a press release on Friday.

The potentially fatal virus is transmitted to people mainly by Culex tarsalis, one of about 50 mosquito species found in Manitoba.

"The potential for human exposure to infected Culex tarsalis mosquitoes is present throughout southern Manitoba," the province stated in its release. 

"The risk of exposure to [West Nile virus] is expected to continue in the coming weeks, particularly if conditions are warm and dry, which is ideal for Culex tarsalis development and activity."

The West Nile threat is not high enough for the province to order municipalities to fog for adult mosquitoes, the province stated. No human cases have been reported this year.

Numbers of nuisance mosquito species — such as the painful biter Aedes vexans, which is not known to transmit potentially harmful pathogens to people — have been low in Winnipeg so far this season.

The city-wide average trap count for Winnipeg on Friday was four mosquitoes. Fogging for nuisance species does not take place until the city-wide average trap count exceeds 25 for two days straight and one quadrant of the city has an average of more than 100.