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West Nile season is back

Durham Region has begun its West Nile Virus surveillance and control activities for the 2020 season.

It’s mosquito season, which means the risk for West Nile virus (WNV) is back.

The Durham Region Health Department has started its WNV surveillance and control activities for the 2020 season.

As part of the ongoing surveillance, the health department will be monitoring WNV concerns across the region, including implementing a weekly adult mosquito-trapping program, a larval mosquito surveillance program, and a larviciding program involving regional catch basins. Stagnant water sites where mosquitos can breed will also be identified.

The health department also routinely traps batches of adult mosquitoes in known mosquito pools, which are then tested for the virus.

In 2019, one mosquito pool tested positive for WNV. This represents a decrease from seven positive mosquito pools that tested positive in 2018.

The health department also uses indicators such as larval mosquito surveillance to determine the risk of the virus for area residents.

West Nile virus is a mosquito-borne disease that spreads to humans through the bite of an infected mosquito. They 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.

The health department suggests residents remove or cover any standing water around their homes to help reduce or eliminate the opportunity for mosquitoes to lay eggs.

WNV has been found in birds, mosquitoes, horses and humans in Ontario since 2001. The Public Health Agency of Canada reported 19 human cases of the virus in Ontario in 2019, compared to 126 human cases in 2018. Durham Region reported five human cases in 2018, there were zero confirmed cases in 2019.

The health department says there are a number of steps residents can take to help minimize the potential breeding sites for mosquitoes, including chlorinating rain barrels or covering them with mosquito screening, and draining water from areas such as pools, chair covers, ceramic pots, wading pools, bird baths, and planters.

In addition, roof gutters should be checked to ensure they are cleared and draining properly, swimming pools and outdoor hot tubs should be cleaned and properly maintained, unused tires should be removed from the property, and drainage ditches should be checked to ensure they are not backed up and holding stagnant water.

In order to reduce the possibility of being exposed to WNV, the health department says to wear shoes, socks and light-coloured clothing with long-sleeves and full-length pants when outside, especially overnight, between dusk and dawn, when mosquitoes are most active.

Insect repellent containing DEET should also be used on exposed skin, doors and windows should have tight-fitting screens, grass, shrubs and hedges should be trimmed, and the compost piles turned over regularly.

For more information about WNV and the health department’s surveillance activities, visit