(CBS) – West Nile mosquitoes are back in the Chicago area for the first time this year.

Those infected mosquitoes were discovered in traps in west suburban Hillside, CBS 2’s Derrick Blakley reports.

The year’s first Illinois mosquito infected with West Nile has Western Springs grandmother Phyllis Stimac concerned for herself — and for her 2-year-old granddaughter Caroline.

“It’s a little alarming that it was discovered so close by,” she says.

The infected mosquito was found in a trap by employees of the Des Plaines Valley Mosquito Abatement District. Experts say it’s an early warning, but too early to get overly worried.

“We get much more concerned if 10 percent or more of the pools we test are positive. That’s when we start to see spillover into the human population,” Paul Geery says.

That usually requires a spell of hot weather, something that hasn’t happened yet in the region.

“Now, if someone got West Nile it’d be very unlucky because there just isn’t that much virus out there,” Geery says.

That doesn’t stop Caroline’s grandmother from being apprehensive.

“It’s scary especially with the little ones like my granddaughter who wait for these days to be able to be outside. You’re always looking over your shoulder,” Stimac says.