Toronto Mosquitoes Test Positive for West Nile Virus: Low Risk of Infection

Toronto Public Health has confirmed positive West Nile virus test results in mosquitos collected in the city. The risk of infection is low if precautions are taken, such as wearing protective clothing, using insect repellent, and eliminating standing water. The virus can cause fever, headache, and body aches, with people over 50 or with weakened immune systems at a higher risk of severe illness.

Toronto Public Health has confirmed that mosquitoes in the city have tested positive for West Nile virus. The findings mark the first positive cases this year after results came back on three batches of mosquitoes collected in the city [1]. The risk of infection is low if precautions are taken, according to Toronto Public Health (TPH).

West Nile virus is transmitted to humans from the bites of infected mosquitoes. Symptoms can take two to 14 days to develop and include fever, headache, nausea, skin rash, and body aches. TPH reports that people over the age of 50 or with weakened immune systems are at a greater risk of severe illness [1].

To minimize the risk of infection, TPH advises residents to take necessary precautions to avoid mosquito bites. These include wearing long, light-coloured clothing, using Health Canada-approved insect repellent, being cautious at dawn and dusk when mosquitoes are most active, and eliminating pools of water on your property [1]. The city conducts annual mosquito surveillance from mid-June until mid-September.

Similar alerts have been issued in other regions. Philadelphia health officials warned residents after West Nile virus was found in mosquitoes in Northeast Philadelphia earlier this month [2]. York Region also reported its first positive test for West Nile Virus in 2025, detected in a Vaughan mosquito trap [3]. The Durham Region Health Department confirmed that adult mosquitoes in Oshawa have tested positive for the virus, marking the second batch in Durham Region this season [4].

The average number of West Nile virus cases in the U.S. varies annually, but in 2022, 1,132 cases were reported [2]. The disease is most common during the summer and early fall months, with peak activity typically occurring in late August through early September [2].

References:
[1] https://www.cbc.ca/news/canada/toronto/toronto-west-nile-2025-1.7588524
[2] https://www.cbsnews.com/philadelphia/news/west-nile-virus-mosquitoes-northeast-philadelphia/
[3] https://www.thespec.com/news/canada/york-region-confirms-first-positive-west-nile-mosquito-test-of-2025/article_54ef4b56-b0fb-531e-875a-7c1835431bc5.html
[4] https://www.durhamregion.com/news/west-nile-virus-confirmed-in-oshawa-mosquitoes-second-batch-in-durham-this-season/article_3e7c98f3-1f2f-5888-9a5e-1e42ce3c0b27.html