Toronto Public Health has received laboratory confirmation that a resident in Toronto has tested positive for West Nile virus (WNV). This is the first human case testing positive for WNV in Toronto for 2017. WNV is mainly transmitted to people through the bite of an infected mosquito.


“The risk of becoming ill from West Nile virus is low, however, now is a good time to remind residents to take the proper precautions to protect themselves from mosquito bites and to minimize the risk of West Nile virus,” said Dr. Barbara Yaffe, Toronto’s Acting Medical Officer of Health.

Toronto Public Health recommends the following prevention measures to reduce the risk of mosquito bites and to discourage mosquitoes from breeding and maturing:

• Wear light-coloured, long-sleeved shirts and pants when outdoors.
• Apply insect repellent containing DEET or icaridin and follow the manufacturer’s instructions.
• Take extra care during peak mosquito biting time (dusk and dawn) by using mosquito repellent and wearing protective clothing.
• Remove standing water from your property, where mosquitoes can breed.
• Ensure your home has tight-fitting screens on windows and doors.

WNV symptoms usually develop between two and 15 days after a person is bitten by an infected mosquito. Symptoms may include fever, headache, nausea, vomiting, body aches, skin rash and swollen lymph glands. If you or a family member has concerns about any symptoms, please contact your health care provider.

Once a week, from mid-June until mid-September, Toronto Public Health sets 40 mosquito traps across the city. The mosquitoes collected are submitted to a laboratory for identification and testing for WNV. As part of the City of Toronto’s WNV mosquito reduction program, City catch basins are treated with larvicide to reduce mosquito breeding.

As of August 23, 2017, 48 mosquito pools have tested positive for WNV. In 2016, Toronto Public Health reported 38 positive mosquito tests and 19 confirmed human cases of WNV.