Manitoba Health reports that seven mosquito samples have tested positive for the West Nile virus during the week of Aug. 1 to 7. Four of these samples were collected in Winnipeg and one each in Boissevain, Russell and Stonewall. So far this year, a total of 11 positive mosquito samples have been found. Based on the current level of infected mosquitoes in these communities, adult mosquito control is not being recommended at this time.
The number of adult Culex tarsalis mosquitoes trapped during the week of Aug. 1 decreased slightly compared to the previous week. Preliminary numbers for the week of Aug. 8 also show a slight decrease.
Numbers of trapped Culex tarsalis mosquitoes still remain relatively high overall, but the proportion of trapped mosquitoes that have tested positive for West Nile virus is relatively low compared to previous years.
With the increased number of infected mosquitoes and the high number of Culex tarsalis overall, the risk of human exposure to West Nile virus is estimated to have increased slightly over last week. In previous years, the peak risk period for human exposure to West Nile virus has been the last two weeks of July and the first three weeks of August.
To date, no human cases of West Nile virus have been identified in Manitoba in the 2010 season.
