Dead bird in Waterloo Region tests positive for West Nile virus

Public Health is keeping a close eye on mosquitoes in Waterloo Region after a bird tested positive for the West Nile virus. CTV’s Colton Wiens explains how.

Region of Waterloo Public Health says a dead bird found the in the community has tested positive for the West Nile virus.

On July 16, their counterparts in Guelph also detected the illness in a deceased crow.

“It is expected to find [West Nile virus] in birds, as they are known carriers of [West Nile virus], but [West Nile virus] is spread to humans through the bite of an infected mosquito and not through a person handling a dead bird,” Region of Waterloo Public Health said in a statement to CTV News.

Infected mosquitoes have been reported in Toronto, Niagara Region and York Region within just the last week.

There are, however, no confirmed human cases of the illness in Ontario.

Region of Waterloo Public Health said they are focused on monitoring efforts.

“Because of the transient nature of birds, we place a higher priority on the weekly mosquito pool testing as a more reliable indicator of the local presence of [West Nile virus]-carrying mosquitos,” their statement continued. “We have not had a positive mosquito pool or human case to date in 2025.”

Public health said anyone who finds a dead bird in Waterloo Region can report it to the Canadian Wildlife Health Cooperative.

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.

Testing in Waterloo Region

Hot, humid weather is the perfect breeding ground for mosquitoes.

Region of Waterloo Public Health said they keep a close eye on the weather and confirmed cases, and adjust their efforts as needed.

“Traps would be increased in the event that there was a hotspot or there was an area of concern,” explained Bernadette Moussa, the region’s acting manager of health protection and healthy environments. “If there were any issues with them, we would assess its location and its environment and change accordingly.”

In all, the health unit manages 16 traps in areas known for being mosquito hot spots.

“We put them up in the afternoon, around 2 p.m., and pick them up the next morning around 10 a.m.,” said Sofia Gavrilova, a student public health inspector for the region. “Then we submit it to the lab where they count how many mosquitoes they have. They identify the species of them, if they’re of concern to transmit the West Nile virus, and they test them for West Nile virus as well.”

Dry ice is placed inside the trap, which attracts mosquitoes as it becomes carbon dioxide gas. A battery-powered fan then traps the insects in a cup.

“It depends on the environmental conditions, but it can be up to 200 [mosquitoes], but it can be as little as two mosquitoes,” Gavrilova said.

Testing results are usually back within a week.

Public health also uses larvicides to eliminate mosquitoes before they develop into potentially virus-carrying adults.

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 water baths, change ornamental ponds at least once to twice weekly,” Moussa suggested.

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.

- With reporting from Colton Wiens and Elianna Lev