Toronto Public Health says it received a laboratory report today indicating that mosquitoes have tested positive for West Nile.
Toronto associate medical health officer Dr. Howard Shapiro says the finding of mosquitoes carrying West Nile is earlier in the season than previous years.
In St. Catharines, environmental health manager Peter Jekel says all Niagara communities should be on alert.
No birds have tested positive for West Nile so far this summer in Niagara and the region has not seen any human cases.
Halton Region Public Health last week reported finding West Nile in two mosquito ponds — in Oakville, Ont., and Milton, Ont.
The West Nile virus first appeared in Toronto in 2001, and in 2002 there were 163 known cases and 11 deaths.
Ontario reported more than 60 human cases in 2011.
(The Canadian Press, CKTB)