A batch of mosquitoes collected in Ajax has tested positive for West Nile virus, marking the first detection of the virus in Durham Region this season. The Durham Region Health Department confirmed the finding on July 17, 2026.
The infected mosquitoes were collected from a trap site in Ajax known as Ajax F2. As of July 13, the site had recorded 1,211 mosquitoes trapped, with one batch coming back positive for the virus.
No human cases of West Nile have been reported in Ontario so far in 2026, but the detection serves as an early reminder that the virus is active. The Health Department collects mosquitoes weekly from 16 trap sites across the region and tests them for the virus from mid-June to mid-September. In total, 13,797 mosquitoes have been trapped across Durham as of mid-July.
Most people infected with West Nile virus show no symptoms. Roughly one in five develop fever, headache, or a rash, and about one in 150 can get a more serious illness like encephalitis or meningitis. Durham saw 21 human cases in 2025 and 18 in 2024.
Nearby health units are also reporting first positive batches. York Region confirmed infected mosquitoes in Markham on July 16, and Toronto reported its first positive test on July 17.
The Health Department recommends residents wear light-coloured long sleeves and pants at dawn and dusk, use insect repellent with DEET, remove standing water from properties, and ensure window screens are in good condition.
