Peel Region confirms first human case of West Nile virus

BRAMPTON, Ont. – September 9, 2025. Peel Public Health has confirmed the first human case of West Nile virus for 2025 in a Mississauga resident.

West Nile virus is transmitted to humans through the bite of an infected mosquito. While most people who contract the disease will show no symptoms, some will experience mild flu-like symptoms such as fever, headache, body aches, mild rash, and swollen lymph glands. In rare cases, West Nile virus can lead to severe illness. People 50 years and older and those with weakened immune systems are at a higher risk of developing serious complications.

West Nile virus activity varies from year to year and is influenced by rainfall and temperatures. Peel Public Health monitors mosquito populations across the region each summer and manages them by treating catch basins and surface water with environmentally friendly larvicides. Mosquitoes in Peel first tested positive for West Nile virus in mid-July this year, and the risk of exposure mosquitoes is highest between July and September.

Residents are encouraged to protect themselves from mosquito bites by:

• Applying an approved insect repellent containing an ingredient effective against mosquitoes, such as DEET or icaridin, to exposed skin and clothing. Read and follow the manufacturer’s directions for safe use. NOTE: Infants 6 months and younger should not use an insect repellent containing DEET or icaridin. Instead, use a mosquito net when babies are outdoors in a crib or stroller.
• Avoiding areas with large mosquito populations and taking extra precautions between dusk and dawn when mosquitoes are most active, and at any time near shady, wooded areas.
• Wearing light-coloured, tightly woven, loose-fitting clothing such as long pants, long-sleeved shirts, shoes and socks to protect exposed skin.
• Making sure all window and door screens fit securely and are free of tears and holes.
• Ensuring that openings to rain barrels are always covered with a screen mesh.
• Removing or draining items on your property that hold stagnant water. Water that is stagnant for more than 7 days is an ideal breeding site for mosquitoes. You can report stagnant water sites to Peel Public Health at 905-799-7700 or online.
• Registering online to receive email notifications and information about where mosquitoes have tested positive for West Nile virus in Peel.
• If you have a backyard catch basin, registering online for treatment in 2026.