Environmental Health

West Nile Virus, a close up picture of a mosquito on a person

West Nile Virus

West Nile Virus (WNV) is a potentially serious illness. It is transmitted to humans through the bite of an infected mosquito. Although the risk of becoming infected is low, protection against mosquito bites reduce this risk even further.

Toronto Public Health carries out mosquito surveillance activities typically from the end of May until the end of September. Mosquito reduction activities are also conducted where immature mosquitoes (larvae) are treated with a larvicide to prevent the larvae from developing into adult mosquitoes which can transmit WNW.

Toronto Public Health monitors and reports weekly mosquito surveillance data on positive mosquito pools and human cases of WNV.

Protecting from West Nile Virus

Person applying deet to their arm

Reducing Risk

Avoid mosquito bites and eliminate stagnant water on your property

Picture of mosquito larvae in a collection cup


City catch basins are treated with larvicide to prevent mosquito development .