Health Department begins 2026 West Nile virus surveillance program

Whitby, Ontario – Durham Region Health Department will begin its West Nile virus (WNV) surveillance and control program for the 2026 season between May 11 and June 8. This program includes surveillance for larval mosquito activity, administering larvicide in catch basins and surface water sites, and adult mosquito trapping to test for WNV throughout Durham Region.

As a reminder, the Health Department will no longer mail forms to private property owners for owners to request larviciding of catch basins located on their properties. Residents can submit a request to the Health Department to have larvicide administered to private property catch basins by completing an online application form at durham.ca/BYCBlarvicide. To submit complaints for stagnant water sites on public property visit durham.ca/ReportStagnantWater.

WNV is a mosquito-borne disease spread to humans through the bite of an infected mosquito: it is not spread from person to person. In 2025, Durham Region reported 21 human cases of the virus and 26 WNV positive mosquito batches identified through the Health Department’s adult mosquito trapping activities.

It is important to eliminate sources of stagnant water to remove breeding sites for mosquitoes which helps to lower the spread of the virus. Residents can help by:

• Applying for larviciding of any backyard catch basins on their property.
• Adding chlorine to rain barrels or cover barrels with mosquito screening.
• Draining water from pools and chair covers, ceramic pots, wading pools, bird baths, planters, etc.
• Checking that roof gutters are cleared and draining properly.
• Cleaning and maintaining swimming pools and outdoor hot tubs.
• Removing any unused tires from your property.
• Ensuring that drainage ditches are not backed up and holding stagnant water.

To help reduce potential exposure to WNV, residents are encouraged to take the following precautions:

• When outside, wear shoes, socks and light-coloured clothing with long sleeves and full-length pants, especially overnight – between dusk and dawn – when mosquitoes are most active.
• Use insect repellent containing Picaridin or DEET on exposed skin, following Health Canada’s safety tips on using personal insect repellents.
• Ensure door and window screens are tight-fitting and in good repair.
• Keep grass, shrubs and hedges trimmed.
• Turn over compost piles regularly.

For more information about WNV and the Health Department’s surveillance activities, please call myDurham 311 (within regional boundaries: 311, outside regional boundaries: 905-668-7711 or 1-800-372-1102). You can also contact the Durham Health Connection Line at 905-668-2020 or 1-800-841-2729 or visit durham.ca/WestNile.

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For more information please contact the Health Department.