First mosquitoes test positive for West Nile virus this season

Ottawa Public Health (OPH) is reminding residents to protect themselves from mosquito bites. Routine mosquito trapping and testing for West Nile virus (WNV) have confirmed a positive mosquito pool in Ottawa. This is the first confirmation of WNV in Ottawa this year since OPH began routine seasonal monitoring in June. There have been no confirmed or probable human cases of West Nile virus reported in Ottawa this year. As of Sunday, July 26, there have been two reported human cases in Ontario this year. 

Mosquitoes can pose a risk for WNV infection until the first hard frosts of the fall. Residents are reminded that even as the weather begins to cool in the fall, there remains an increased risk for human WNV infection. Residents are also asked to help reduce mosquito breeding sites around their homes by removing any unnecessary standing water and regularly treating or replacing water in use, like ornamental pools or bird baths. 

West Nile virus is an infection spread primarily by the northern house mosquito (Culex pipiens). Most people will not develop any symptoms if infected with WNV but about 20 per cent may experience flu-like symptoms such as a fever, headache, muscle aches and possibly a rash, that usually appears two to fourteen days after being bitten by an infected mosquito. Less than one per cent of WNV infections lead to very serious illness, in which WNV invades the central nervous system (brain and spinal cord). This risk is higher in people with weakened immune systems and risk increases with age.

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 (follow manufacturer’s instructions)
• Protecting yourself between dusk and dawn especially, 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 tightly fitted screen mesh at all times  

Spending time outdoors has many health benefits; however, urban settings, including on and around home porches, apartment balconies, in gardens, and in local parks, are ideal for the mosquitoes that transmit West Nile virus. Be sure to protect yourself against mosquito bites around your home so that you can enjoy the warm weather safely.  

Ottawa Public Health’s proactive approach to West Nile virus includes weekly mosquito surveillance to monitor virus activity and assess the risk to residents. OPH, in collaboration with partners, regularly applies larvicide in City-owned roadside storm sewer catch-basins to reduce populations of mosquitoes that spread West Nile virus. When necessary, mosquito larvicidal treatment may also be applied to other standing water sites on City property, such as ditches and storm water management ponds. 

 Visit Ottawa Public Health's West Nile virus page to learn more about West Nile virus. Residents can also connect with OPH on Facebook, Instagram, Bluesky and YouTube.