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 2024, a total of 14 confirmed human cases of West Nile virus were reported in Toronto.
As of July 31st, 2025, one human case of West Nile virus and 16 positive pools were reported.
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.
If you require assistance in accessing or interpreting communicable disease surveillance information or data, please contact the Epidemiology and Data Analytics Unit by email (edau@toronto.ca).