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 mosquitos for identification and West Nile virus (WNV) testing. In 2023, there were 83 positive pools, the second highest amount since the program started collecting this data in 2002.

In 2023, a total of 22 confirmed human cases of West Nile virus were reported in Toronto.

Human Case Surveillance

Confirmed and suspected human cases of WNV illness for Toronto residents are reportable to Toronto’s Medical Officer of Health and are investigated by Toronto Public Health.

WNV Surveillance Bulletins describe human cases of WNV illness that have been reported to Toronto Public Health and provides updates on mosquito surveillance activities in Toronto. These bulletins are posted to update health professionals and the public health community with comprehensive epidemiologic information on WNV illness in Toronto. The reports will be posted should sufficient cases be reported.

Subscribe to Toronto Public Health’s West Nile Virus e-Bulletin

West Nile Virus Reports

If you require assistance in accessing or interpreting communicable disease surveillance information or data, please contact the Communicable Disease Surveillance Unit by phone (416-392-7411) or email ( during business hours (Monday to Friday, 8:30 a.m. to 4:30 p.m.).