Toronto — Toronto Public Health (TPH) has confirmed that three mosquito batches collected in the city have tested positive for West Nile virus (WNV) — the first positive results of the season.
The virus, which is spread to humans through the bite of an infected mosquito, typically appears in the city during warmer months. While the risk of infection remains low, TPH is urging residents to take extra precautions as mosquito activity ramps up during the summer.
Citywide Mosquito Surveillance Underway
TPH’s annual mosquito surveillance program runs from mid-June through mid-September, using 22 mosquito traps across the city to collect samples. These are sent to a lab, grouped into batches (called “pools”) and tested for WNV. This week’s findings are the first positives of the 2025 surveillance cycle.
How to Protect Yourself
TPH advises the public to take the following steps to reduce the risk of mosquito bites:
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Wear light-coloured clothing with long sleeves and pants outdoors.
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Apply Health Canada-approved insect repellent and follow directions carefully.
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Be extra cautious at dawn and dusk, when mosquitoes are most active.
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Ensure that window and door screens are in good condition.
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Remove standing water around your home — including in buckets, toys, pool covers, and planters.
What to Watch For
Symptoms of West Nile virus usually develop between 2 to 14 days after a bite and can include:
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Fever
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Headache
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Nausea or vomiting
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Body aches
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Swollen lymph nodes
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Skin rash
While most cases are mild, those over 50 or with weakened immune systems are at a greater risk for serious illness. Anyone experiencing symptoms is advised to contact a healthcare provider.
More details and prevention tips are available on the City’s West Nile Virus webpage at toronto.ca/west-nile-virus.
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