Manitoba sees 1st West Nile-infected mosquitoes this year

Manitoba health officials say the first Culex tarsalis mosquitoes infected with West Nile virus this year have appeared in the province, but there are no human cases of the virus so far this year.

The infected insects were found in a mosquito trap in Portage la Prairie, Man., last week, the province announced Friday.

At this time, no human cases of West Nile Virus have been identified in Manitoba, the province said, adding that there are currently no mosquito fogging orders in Portage or anywhere else.

Health officials say most of the mosquitoes being collected in traps so far this summer are adult nuisance mosquitoes that do not carry West Nile virus.

At the same time, they say the number of Culex tarsalis mosquitoes — the type that can transmit West Nile virus — is growing in some communities, especially in the southern part of the Prairie Mountain Health Region.

"The risk of exposure to WNV is expected to increase in the coming weeks, particularly if warm nighttime temperatures persist, as these are ideal conditions for Culex tarsalis development and activity," the province said in a news release.

"Manitobans are cautioned the province is entering what has historically been the highest risk period for WNV transmission."

Still, officials say Culex tarsalis mosquito numbers are lower compared to this time last year and lower than 2007, when the province had multiple West Nile infections in humans.