West Nile virus (WNV) is a potentially serious illness that is transmitted to humans through the bite of an infected mosquito. Although the risk of becoming infected with WNV in Toronto is low, protecting yourself against mosquito bites can help reduce the risk even further.
The City of Toronto website has information on reducing the risk of West Nile Virus.
West Nile Surveillance and Reporting
Toronto Public Health conducts mosquito surveillance from mid-June until mid-September every year. Once a week, 22 mosquito traps are set across the city to collect mosquitoes for identification and West Nile virus (WNV) testing. For recent surveillance results and information, visit the City website.
City Larviciding Program
The City of Toronto Larviciding Program of city catch basins to prevent immature mosquitoes (larvae) from developing into adult mosquitoes that can transmit WNV began on June 10, 2016.
Larviciding is one measure that helps reduce mosquito breeding and control adult mosquito populations by using pesticides (larvicide) to impede mosquito larvae development. The larvicide is applied by licensed applicators and/or trained technicians approved by the Ontario Ministry of the Environment, Conservation and Parks and under the authority of Toronto's Medical Officer of Health. The larviciding program is designed to reduce the mosquito population and the associated health risks from WNV.
Larvicide is typically applied from June to the end of August, however the exact start date will depend on larvae mosquito surveillance results.
Further information is available on the City of Toronto Larviciding program.
Health and Environmental Impacts
The larvicides used by the City of Toronto break down quickly in the environment and are harmless to plants, mammals, fish, birds and insects other than mosquitoes and blackflies. Methoprene and BS are not harmful to humans when used to control mosquitoes.
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