Photo by Jaime Dantas on Unsplash.

Grey Bruce Public Health (GBPH) has been notified that an American crow from Grey-Bruce has tested positive for the mosquito-borne West Nile Virus (WNV).

In an August 21, 2024 media release, the crow was submitted to the Canadian Wildlife Health Co-operative for testing earlier this month. Crows are known carriers of WNV.

While the risk to humans of acquiring the virus in Grey-Bruce remains low, this finding serves as a reminder of the importance of taking steps to prevent mosquito bites.

Senior Public Health Manager Andrew Barton said that people are most at risk of becoming infected with West Nile Virus in late summer.

"The single most effective way to prevent the virus is to prevent mosquito bites, such as by using insect repellent containing DEET or Incaridin and covering exposed skin while outdoors, particularly at dusk and dawn when mosquitoes are most active,” he said.

This is the first bird to test positive for WNV in Grey-Bruce in 2024.

According to Public Health Ontario data, as of August 17, six Ontario residents have tested positive for WNV. No human cases of the virus have been reported in Grey-Bruce.

WNV circulates between birds and some species of mosquitoes and can be transmitted to humans by a mosquito bite if the mosquito has first bitten an infected bird.

GBPH sets mosquito traps monthly, from May to September, in each Grey-Bruce municipality as part of its West Nile surveillance program. The traps are sent to a laboratory for species identification and viral testing.

So far this year, no positive mosquito pools have been identified in Grey-Bruce. Public Health has set up additional traps in the area where the dead crow was located.

Other ways to prevent mosquito bites and, in turn, prevent WNV, include:

wearing light-coloured long pants and long sleeves, socks, and a hat when outdoors;
reducing mosquito habitats near the home by eliminating standing water in flowerpots, eavestroughs, etc.;
taking extra protection measures between dusk and dawn when mosquitoes are most active; and
ensuring door and window screens fit securely and are free of holes.

Most people infected with WNV do not experience any symptoms. Others see symptoms two to 15 days after being bitten by an infected mosquito. Symptoms are usually mild and can include a fever and headache; however, serious symptoms can occur.

Some people are at greater risk for serious health effects from West Nile virus. These include people:

over the age of 50;
with chronic diseases, such as cancer, diabetes, alcoholism, and heart disease;
who require medical treatment that may weaken their immune system, such as chemotherapy.

Anyone with concerns about a dead bird can contact the Canadian Wildlife Health Co-operative at 1-866-673-4781.