First mosquitoes test positive for West Nile virus this season


Ottawa Public Health reminds residents to protect themselves from mosquito bites.

Mosquito trapping and testing as part of Ottawa Public Health’s West Nile virus program have confirmed the first positive West Nile virus lab result in Ottawa mosquitoes for this season. Biting mosquitoes can pose a risk for West Nile virus until the first hard frosts of the fall. Residents can help reduce mosquito populations around their homes by getting rid of all outdoor objects that can hold water, where mosquitoes lay their eggs.

West Nile virus is an infection spread primarily by the northern house mosquito (Culex pipiens). Most people will not develop any symptoms if infected, but about 20 per cent may experience flu-like symptoms, including fever, headache, muscle aches and possibly a rash. The risk of more serious illness in which West Nile virus invades the central nervous system, increases with age, with older adults and people with weakened immune systems being at higher risk. Serious illness occurs in less than one per cent of infections.

There have been no reported, confirmed, or probable human cases of West Nile virus in Ottawa this year. As of September 4, there have been three reported human cases in Ontario this year.

Protect yourself and your family from mosquito bites by:

  • Applying a Health Canada-approved mosquito repellent containing DEET or icaridin to exposed skin and to clothing
  • Protecting yourself especially between dusk and dawn, when mosquitoes are most active, and at all times in or near shady, bushy, or wooded areas
  • Wearing light-coloured, tightly woven, loose-fitting clothing, including long pants, a long-sleeved shirt, shoes and socks to protect exposed skin
  • Making sure all windows and doors in your home have well-fitting screens that are in good condition
  • Reducing standing water sites around your home, such as bird baths, toys, flowerpot saucers, swimming pool covers, old tires, wheelbarrows, buckets, and cans – anything that can hold water for seven days or longer
  • Keeping all openings to rain barrels covered with screen mesh at all times

Spending time outdoors has many health benefits. Due to the COVID-19 pandemic, more people are spending time outdoors in urban settings, including on their porches, in their gardens, and in local parks. These settings are ideal for the mosquitoes that transmit West Nile virus. Be sure to protect yourself against mosquito bites around your home.

Ottawa Public Health has a proactive plan to address West Nile virus that includes weekly surveillance and, when necessary, mosquito larvicidal treatment of standing water on City property, such as ditches and storm water management ponds. Ottawa Public Health also regularly applies larvicide in City-owned roadside storm sewer catch-basins to reduce the mosquito population and the risk of West Nile virus.

For more information on West Nile virus, visit or call Ottawa Public Health at 613-580-6744 (TTY: 613-580-9656). You can also connect with us on Facebook, Twitter, and Instagram.

For more information on City programs and services, visit or call 3-1-1 (TTY: 613-580-2401). You can also connect with us through Facebook, Twitter and Instagram.