Mosquitoes trapped in Pickering have tested positive for West Nile virus, the Durham Region Health Department said.

The positive batch was collected from one of the Health Department's mosquito trap sites in the city, according to the Region of Durham. A second positive batch was found in Whitby, bringing the region's total to 21 positive mosquito batches so far this season.

Positive results previously found in Ajax, Clarington and Oshawa

Earlier positive batches this year were detected in Ajax, Clarington and Oshawa, according to the Region of Durham.

Every week between June and September, the Health Department sets mosquito traps across Durham and submits the insects it collects for laboratory testing. The department also treats catch basins and other stagnant water sites in the region with a larvicide to reduce mosquito breeding.

What residents should know about the virus

West Nile virus is a mosquito-borne disease spread to humans through the bite of an infected mosquito, the Durham Region Health Department said. Mosquitoes become infected by feeding on the blood of a bird carrying the virus. The disease does not pass from person to person, or from bird to person.

According to the Region, most people who contract the virus experience mild illness, including fever, headache, body aches, nausea, vomiting and a rash on the chest, stomach or back.

More serious symptoms can include muscle weakness, a stiff neck, confusion, tremors, numbness and sudden sensitivity to light. Symptoms usually develop between two and 15 days after a bite from an infected mosquito.

While the Health Department says the risk of becoming infected is low, it recommends residents take precautions to minimize mosquito bites and reduce the possibility of infection.

Where to get more information

Residents looking for more information on West Nile virus can call the Durham Health Connection Line at 905-668-2020 or 1-800-841-2729, or visit durham.ca/WestNile.

This story will be updated if further positive mosquito batches are identified in Pickering or elsewhere in Durham Region.