West Nile virus found in Toronto mosquitoes, risk remains low: officials

West Nile virus has been detected in a group of mosquitoes collected in Toronto, but public health officials say the risk to humans remains low.

The mosquitoes were trapped in northwest Scarborough and represent the first scourge to test positive for the virus in 2023, Toronto Public Health (TPH) said in a news release issued Tuesday.

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As it does every year, TPH conducts mosquito surveillance from mid-June to mid-September by setting 22 traps across the city. Those traps are then submitted to a laboratory for identification and tested for the virus.

In 2022, TPH said, 14 mosquito pools tested positive for West Nile. Twenty mosquito pools tested positive for West Nile in 2021 and 33 pools were flagged for the virus in 2020.

“The risk of becoming infected with West Nile virus continues to be low in Toronto, however there are some simple steps residents can take to further reduce their risk when enjoying the summer,” Toronto’s Medical Officer of Health Dr. Eileen de Villa said.

“These steps 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.”

• READ MORE: How to stop yourself being bitten by mosquitoes this summer

Symptoms of West Nile virus usually develop between two and 14 days after a person is infected, TPH said. Those symptoms may include fever, headache, nausea, vomiting, body aches, skin rash and swollen lymph glands.

Populations at higher risk of severe illness include older individuals and those with compromised immune systems, TPH said.

For a full list of tips to prevent infection and more information about West Nile virus, click here.