Anyone can become infected with West Nile virus, Toronto Public Health is warning, though less than one per cent of people with the virus become sick enough to be hospitalized, and only one in 1,000 people may die.

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West Nile virus is a potentially serious illness that is transmitted to humans through the bite of an infected mosquito. Although the risk of becoming infected is low, protection against mosquito bites can reduce this risk even further.

But regardless of the chances, the city and the Canadian Centre of Mosquito Management are reminding people to be aware of the virus this summer. West Nile virus is a potentially serious illness that is transmitted to humans through the bite of an infected mosquito. Although the risk of becoming infected is low, protection against mosquito bites can reduce this risk even further.

According to the city, Culex mosquitoes are the most common carriers of West Nile virus in Southern Ontario. These types of mosquitoes prefer to bite birds, but will also bite humans. Storm water catch basins have been identified as significant breeding sites for Culex mosquitoes.

The first step to avoid getting the virus is to avoid mosquito bites. Public Health recommends:

  • Stay indoors during peak mosquito activity, usually at dusk and dawn.
  • Wear light-coloured clothing, long pants, long-sleeved shirts, socks and a hat.
  • Use mosquito repellent.
  • Avoid areas with large numbers of mosquitoes.

Toronto Public Health says clearing standing water keeps mosquito populations lower. It says the following steps will help:

  • Keep your yard clean: Uncovered garbage containers and junk piles collect water in which mosquitoes can breed.
  • Always inspect pools and ponds: Poorly maintained pools and swimming pools can be breeding sites for mosquitoes.
  • Clean out eaves, gutters and drains: Clogged gutters will accumulate water and create a place for mosquitoes to breed. Check flat roofs frequently for standing water.
  • Eliminate stagnant water: Clean up and empty water in toys, birdbaths, tires, flowerpots, wheel barrows and other garden objects where mosquitoes can breed.
  • Maintain yards and lawns: Fill in low depressions in lawn areas. Eliminate standing water in gutters or storm drains to prevent small ponds. Install screens over catch basins. Turn compost over frequently.
  • Fix faucets and hoses: Repair any leaks to faucets and hoses to prevent possible breeding sites. Prevent water from pooling around downspouts and air conditioners.
  • Repair window screens and screen doors: Crawl spaces, attic vents, and broken screens allow mosquitoes to enter your home. If you don’t have screens, try to keep windows closed between dusk and dawn.
Map of mosquito risks around the house

A diagram of where mosquitoes are most likely to breed around the house. (City of Toronto)

Click here to see a larger diagram of where mosquitoes may be breeding on your property.

In addition to prevention, the city will use pesticides or "larvicides" to reduce mosquito breeding and control adult mosquito populations by stopping larvae from maturing. 

Larvicide is applied by licensed applicators and/or trained technicians approved by the Ontario Ministry of the Environment.