Mosquitoes in Toronto test positive for West Nile virus

One batch of mosquitoes from 22 traps set across the city tested positive, the first cases in Toronto this year.

Toronto Public Health has confirmed that some mosquitoes in the city have tested positive for West Nile virus, the first cases found this year. “One batch of mosquitoes” tested positive for the virus, which can be transmitted to people through the bite of an infected mosquito, according to a news release. “Every year, TPH conducts mosquito surveillance from mid-June until mid-September and once a week, 22 traps are set across Toronto,” the health agency wrote.

The infected mosquitoes found in Toronto are among others found in the region: Mosquitoes carrying the virus were recently found in Markham while others in Halton Region tested positive for the virus in early July. “The risk of getting infected with West Nile virus in Toronto is low,” TPH said, but advised residents to take precautions to avoid mosquito bites, including by wearing long and light-coloured clothing outdoors and applying insect repellent.

According to the Public Health Agency of Canada , 70 to 80 per cent of people infected with West Nile virus do not develop symptoms. For those with symptoms, they typically appear within two to 15 days after infection. Mild symptoms can include fever, headache, body aches, a mild rash or swollen lymph nodes.

In rare cases, a bite from an infected mosquito can lead to severe illness affecting the brain or nervous system. Adults aged 50 years and older and individuals with compromised immune systems are at higher risk of severe illness, according to TPH. There is currently no vaccine licensed to treat the virus.