The mosquitoes crashing your backyard barbecue this week are more than an itchy nuisance. Public health units across Ontario have started finding West Nile virus in local mosquitoes, which is the yearly signal that the virus is circulating close to home. Toronto, Windsor-Essex, Belleville, York Region, and Halton Region have all reported positive mosquito pools this season, and so far no human cases have been reported in those regions. This is a quick guide to what that means, who is most at risk, and the small habits that lower your odds of a bite.
Why Is West Nile Virus Showing Up Right Now?
Mid-to-late summer is peak mosquito season in Canada, and infectious diseases specialist Dr. Isaac Bogoch of the University of Toronto told Global News that a handful of positive pools at this point in the year is exactly what you would expect. The cycle is simpler than it sounds. Birds are the natural hosts for the virus. Mosquitoes pick it up when they bite an infected bird, then pass it to people through their own bites, which is why it cannot spread from person to person through everyday contact. This season, positive West Nile virus pools have turned up across the region: Toronto has confirmed one batch of mosquitoes, Windsor-Essex and the Belleville area one pool each, York Region two positive traps and two pools in Markham, and Halton two pools during the week of July 13 to 19. Across Canada, 14 dead wild birds have tested positive, 13 in Ontario and one in Manitoba.
What Does West Nile Virus Do to Your Body?
Most people who catch it never feel a thing. For those who do, Dr. Bogoch describes the usual West Nile virus symptoms as a few days of headache, fever, and chills, followed by recovery. Toronto Public Health adds that nausea, body aches, a skin rash, or swollen glands can show up too, usually two to 14 days after a bite. A small share of infections turn serious, moving into the nervous system and causing muscle weakness or other nerve-related problems. Older adults and people with weakened immune systems face the highest risk of severe illness, so if that describes you or someone you care for, the prevention steps below matter a little more.
How Do You Protect Yourself From Mosquito Bites?
None of this is a reason to hide indoors, and Dr. Bogoch was clear that people should still get outside and enjoy the sunshine. To prevent mosquito bites, wear long, light clothing and use a repellent with DEET or icaridin, especially at dawn and dusk when mosquitoes are most active. Walk your property and tip out any standing water, since birdbaths, plant saucers, clogged gutters, and kiddie pools are all prime breeding spots. If you find a dead bird, do not handle it with bare hands; use gloves or a shovel, or contact your municipality or local public health unit for guidance. The same summer vigilance helps with other seasonal risks, from the sharp rise in tick reports across Canada to the heat-exhaustion symptoms worth taking seriously, and staying on top of Canada's summer measles cases as well.
Frequently Asked Questions About West Nile Virus
Can you catch West Nile virus from another person?
No. West Nile virus spreads through the bite of an infected mosquito, not through casual contact. Mosquitoes become carriers after feeding on infected birds, then pass the virus to people. You cannot catch it from a family member, a coworker, or a handshake, which is why prevention focuses entirely on avoiding bites.
What are the early symptoms of West Nile virus?
Most people have none at all. When symptoms appear, they usually start two to 14 days after a bite and include headache, fever, chills, body aches, nausea, or a rash. Most people recover on their own. Rarely, the virus affects the nervous system, which needs prompt medical care.
Who is most at risk of serious illness?
Adults over 50 and people with weakened immune systems face the greatest risk of severe West Nile illness. For most healthy adults, the risk stays low, but the same prevention steps- repellent, covering up at dusk, and clearing standing water- protect everyone in the household.
If Something Feels Off
If you develop a fever, headache, or unusual fatigue after being bitten and it is not settling, do not sit on it. You can use Medimap to find a walk-in clinic near you and get checked without the guesswork, or browse more seasonal health guides on the Health Hub.
If this is a medical emergency, call 911 or go to your nearest emergency department.
This article is for general information only and is not medical advice. It does not replace a conversation with a qualified healthcare provider about your own health.
Find an allergy or specialist clinic near you? Search through Medimap — no referral needed.
Search clinics →