West Nile Virus Risk Assessment

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In 2003, Toronto and Region Conservation Authority (TRCA) initiated the West Nile Virus Surveillance and Monitoring Program as a measure of due diligence and in cooperation with our Regional Public Health partners in Durham, Peel, York and the City of Toronto.

Program Update

June 23, 2026

TRCA will continue to investigate reports of mosquitoes and standing water in response to complaints on properties it owns or manages.

West Nile Virus monitoring reports from 2003 to 2025 remain available.

TRCA will continue to provide resources and training on larval mosquito identification and will support the distribution of information from local Public Health Units regarding mosquito-borne diseases.

For the most up-to-date information on West Nile Virus risks and protective measures, please contact your local Public Health Unit.

TRCA biologist monitors mosquito population in a wetland area
From 2003 to 2025, TRCA monitored mosquito populations in natural wetlands and stormwater management ponds on its properties. The data collected were used to identify sites containing large numbers of mosquito larvae capable of transmitting West Nile Virus as biting adults.

More Information

TRCA West Nile Virus Larval Mosquito Surveillance
Regional Public Health Units

Contact

TRCA Watershed Planning and Ecosystem Science: wpes@trca.ca