Mosquitoes in Waterloo Region test positive for West Nile virus

A mosquito trap in Waterloo on July 22, 2025. (Colton Wiens/CTV News)

Region of Waterloo Public Health says three mosquitoes, captured in its surveillance traps, have tested positive for the West Nile virus.

One was in Cambridge, another was in Kitchener and the third was in Wilmot.

“These are the first mosquitoes in the region to test positive in 2025,” a media release said. “There have been no reported human cases of West Nile virus in Waterloo Region to date in 2025.”

While the mosquitoes are the first ones to test positive locally, West Nile virus was found in a dead bird back in July.

A human case of the illness was also reported in Hamilton on Aug. 18.

Public health is urging people to stay safe while spending time outdoors.

What is West Nile virus?

The West Nile virus could potentially cause death.

It is primarily transmitted to humans by mosquitoes that have fed on an infected bird. There is no human-to-human transfer of the illness.

Most people who get the virus experience no symptoms. Others may get a fever, headache, body aches, mild rash and swollen lymph glands. Recovery can take about a week.

In the most serious cases, it can cause a severe headache, high fever, stiff neck, nausea, vomiting, trouble swallowing, drowsiness, confusion, loss of consciousness, lack of co-ordination, muscle weakness or paralysis. These can last months or even years after infection.

According to Health Canada, less than one per cent of people will develop severe symptoms that affect the central nervous system.

Protecting against West Nile

Mosquitoes breed in standing water, so homeowners are advised to check around their property for places where water collects, including bird baths, flowerpots, pool covers, eavestroughs and gutters.

Change the water in outdoor baths and ornamental ponds at least once or twice a week.

Also make sure all windows and doors have screens.

Mosquitoes are most active at dawn and dusk. Anyone heading outdoors, especially during those times, is urged to wear a light-coloured long-sleeved shirt and pants.

Using an insect repellent that contains DEET is also commended.