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Second positive testing for West Nile found in Durham

By Dave Flaherty/The Oshawa Express

Durham Region Health Department has confirmed the second positive testing for West Nile Virus in trapped mosquitoes in the past few weeks.

And while there have been no confirmed cases of West Nile virus in humans in Durham Region so far this year, senior public health inspector Toni Moran says that doesn’t necessarily mean it hasn’t happened.

“A lot of people may get West Nile Virus and never know it. Very few people get the most serious side effects, and it tends to be seniors, smaller children and people with undermined immune systems,” Moran says. “It’s usually underreported because they recover.”

According to Public Health Ontario, there have been 64 positively-tested pools and four confirmed human cases of West Nile Virus province wide so far this year.

In comparison, to this date in 2016, there were only eight positive pools and two confirmed human cases.

As reported earlier in The Express, the first positive testing was confirmed on July 20 from a pool collected in a trap in Oshawa.

There were 10 confirmed cases of West Nile Virus-positive mosquitoes in Durham Region in 2016.

Moran says while the amount of confirmed cases are down so far this year, it is difficult to compare to last year until the testing season is over.

“We could have a bunch of [positive] pools in the future,” Moran says.

There have been 9,700 mosquitoes captured to date in 2017.

“We only had 9,300 all of last year,” Moran says.

Moran says this summer’s weather is having an interesting effect on local mosquito populations.

“Normally when there is a lot of rain, there is a lot of standing water [where mosquitoes breed],” Moran says. “However, it’s been such heavy rainfall that it’s disturbed the water surface and the mosquito larvae, they actually drown.”

The cooler weather in the early stages of summer is another factor to consider, Moran says.

“It tends to slow down the mosquito breeding and also slows down the proliferation of West Nile Virus,” she says.

However, Moran says with increasingly hot weather, the potential for an increase in the number of infected mosquitoes remains.

For more information on West Nile Virus, call the health department’s Environmental Health Line at 905-723-3818 or 1-888-777-9613, or visit or