EVANSTON, Ill. (CBS) – Chicago area communities are working to combat the spread of the potentially deadly West Nile virus, but authorities urge pet owners to take precautions during mosquito-abatement measures.

There are now 45 human cases in Illinois, and at least six of them are in Evanston.

Crews will spray there and in the neighboring community of Wilmette. The spray has been used for decades, but officials want families and their pets to limit their exposure to it, CBS 2’s Pamela Jones reports.

Every night Scooter needs his walk along the streets of Evanston. He got that walk out of the way before workers started to spray insecticide for mosquitos tonight.

Some families say the spraying means they’ll be keeping pets like Pepper indoors.

In fact, pet owners in Evanston and Wilmette are being advised to keep pets inside and keep windows shut while workers spray.

The Stein family rounded up their five feline friends on Monday.

They’re using a synthetic insecticide that specifically targets adult mosquitoes that can carry west Nile virus.

The North Shore Mosquito Abatement District says the chemical lingers in the air for about 45 minutes and then begins to dissipate.