Toronto Public Health confirms first mosquitos in 2023 to test positive for West Nile virus

West Nile Virus. Image credit:

#Toronto; #WestNileVirus; #TorontoWNVPositive

Toronto/CMEDIA: Confirmation of one batch of mosquitoes that tested positive for West Nile Virus (WNV) has been received by Toronto Public Health (TPH), a news release said.

Collected from a northwest Scarborough location, these mosquitoes are the first to test positive for WNV in Toronto this year.

WNV is an infection transmitted to people through the bite of an infected mosquito.

Surveillance on mosquitoes is conducted by TPH  from mid-June until mid-September every year by setting 22 mosquito traps across the city once a week to collect mosquitoes that are then submitted to a laboratory for identification and grouped by the lab into pools to test for WNV. 

A total of 14 positive mosquito pools were reported in 2022 .

Although the risk of getting infected in Toronto is currently low, residents are being advised by TPH to take the precautions to avoid bites from infected mosquitoes including wearing light-coloured clothing, long pants and long-sleeved shirts when outdoors, applying insect repellent; making sure homes have tight-fitting screens on windows and doors, and removing standing water from properties, where mosquitoes can breed.

“The risk of becoming infected…low in Toronto, however there are some simple steps residents…include wearing insect repellent and light-coloured clothing to protect against bites by infected mosquitoes, using tight-fitting screens on windows and doors to prevent mosquitoes from entering the home and removing standing water where mosquitoes can breed,”  Dr. Eileen de Villa, Medical Officer of Health said.

Symptoms of WNV including fever, headache, nausea, vomiting, body aches, skin rash and swollen lymph glands usually develop between two and 14 days after a person is bitten by an infected mosquito with older individuals or individuals with compromised immune systems are at higher risk of severe illness. 

Anyone developing symptoms are being advised to contact their health care provider.