Health Department begins 2023 West Nile virus surveillance activities

Durham Region Health Department has started West Nile virus surveillance and control activities for the season.

West Nile virus is a mosquito-borne disease that is spread to humans through the bite of an infected mosquito. Mosquitoes become infected by feeding on the blood of birds that carry the virus. The disease is not passed from person to person or from bird to person. Since 2001, West Nile virus has been found in birds, mosquitoes, horses and humans in Ontario. In 2022, Durham Region had one confirmed and two probable human cases of West Nile Virus.

The Health Department routinely traps batches of adult mosquitoes to test for West Nile virus. In 2022, 15 mosquito batches trapped by the Health Department tested positive – an increase from 2021 when there were 10 batches of mosquitoes that tested positive. The Health Department also conducts larval mosquito surveillance, as well as a larviciding program involving Regional catch basins.

Covering standing water can help reduce or eliminate the opportunity for mosquitoes to lay eggs that develop into larvae and, ultimately, become mosquitoes which can spread the virus. Residents can help by:

• Chlorinating rain barrels or cover them with mosquito screening.
• Draining water from pool 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 West Nile virus, 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 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 West Nile virus and the Health Department’s surveillance activities, please call Durham Health Connection Line at 905-668-2020 or 1-800-841-2729, or visit durham.ca/WestNile.