The city of Plano has identified the West Nile virus in two mosquito-testing traps, prompting the city to spray for mosquitoes later this week.

The city will spray the areas, one in east Plano and another in the southern part of the city, starting at 9 p.m. Thursday.

The first area where the city will spray for adult mosquitoes is a large residential neighborhood straddling Shiloh Road, located generally south of Park Boulevard and north of 14th Street in east Plano.

The other area subject to sprays is in a mostly commercial district in south Plano near the intersection of Coit Road and Plano Parkway.

Although humans rarely contract West Nile virus—states reported fewer than 2,000 human cases to the Centers for Disease Control and Prevention in 2016—it can be life-threatening for the 1 percent of human cases that result in a serious neurological condition. People age 60 and older bear the most risk, according to the agency.

The city advises residents near the spray areas to keep pets and children indoors starting at 9 p.m. Thursday.

For detailed boundaries of the spray areas, zoom in on one of the red zones in the map below.