The Washoe County Health District will conduct its final aerial abatement operation of the 2017 mosquito season on September 20 and 21 beginning at 6:30 am in the North Valleys area. Helicopter applications of Vectolex larvicide will be applied to over 2,500 acres of wetlands from Silver Lake to Washoe Lake, including areas surrounding Swan Lake and Lemmon Valley, Kiley Ranch and Spanish Springs, Rosewood Lakes, Butler Ranch, South Meadows, Damonte Ranch, and Washoe Valley. According to health officials this application is necessary, due to the continued reporting of positive human and animal West Nile Virus cases. Besides a dozen confirmed human cases, several birds and a horse have also been identified with the virus this season.