Toronto’s first reported human case of West Nile virus in 2026 confirms that the virus is circulating during the city’s highest-risk mosquito season, but one case does not amount to an outbreak.
Toronto Public Health said Thursday that an adult resident had become the city’s first reported human case of the year. The agency provided no information about the resident’s condition, whether the person was hospitalized, or where the infection may have occurred.
The announcement followed Toronto’s first positive mosquito test of the season. One batch collected through the city’s surveillance program tested positive for West Nile virus on July 17. Toronto operates 22 traps each week from mid-June through mid-September, then submits captured mosquitoes for identification and laboratory testing.
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The sequence is consistent with the virus’s regular summer return. Canadian health authorities identify mid-July through early September as the period when humans face the greatest risk, with exposure continuing until the first hard frost. Mosquitoes are particularly active around dawn and dusk.
West Nile virus circulates mainly between birds and mosquitoes. A mosquito typically becomes infected after feeding on a bird carrying the virus, then passes it to a person or another animal through a later bite.
The virus is not spread through ordinary contact such as touching, kissing, or caring for an infected person. Transmission through blood transfusions, organ transplants, pregnancy, or breast milk is possible, but considered very rare. Canadian blood donations are routinely tested for the virus.
For most people, an infected bite does not lead to noticeable illness. The Public Health Agency of Canada estimates that 70% to 80% of infected people develop no symptoms. Others may experience fever, headache, body aches, nausea, vomiting, a rash, or swollen lymph glands. Symptoms generally begin within roughly two weeks of infection.
Fewer than 1% of infected people develop serious health effects, according to the federal agency. Severe infections can affect the brain and spinal cord, causing meningitis, encephalitis, muscle weakness, loss of coordination, paralysis, confusion, or loss of consciousness. Some severe cases can be fatal or leave patients with lasting neurological problems.
Toronto has dealt with substantially more than one case in recent seasons. The city recorded 14 confirmed human cases in 2024 and 26 cases as of September 9, 2025.
There is no approved human vaccine or specific antiviral treatment for West Nile virus. Mild cases are generally managed through symptom relief, while severe cases may require hospitalization, intravenous fluids, medication, or breathing support.
Prevention therefore depends mainly on avoiding mosquito bites. Public-health guidance recommends using Health Canada-approved repellents containing DEET or icaridin, wearing long sleeves and pants, repairing window screens, and taking extra care at dawn and dusk.
