CHICAGO (CBS) — It’s gearing up to be one of the worst years ever for West Nile Virus.

The U.S. Centers for Disease Control and Prevention has said there have been 1,118 cases of West Nile so far this year. That’s three times the normal amount for this time of the year.

Illinois has had 27 cases this year.

CBS 2’s Dana Kozlov has more on when the city decides to spray for mosquitoes, and where.

LISTEN: WBBM Newsradio’s Regine Schlesinger reports

It all depends on where West Nile-carrying mosquitoes are found. The city has been tracking that for months, but some residents wonder if data should be the only gauge.

Whether it’s sending out trucks to spray mosquito killer, or individuals using insect repellent when they go outdoors, local health officials say spraying against mosquitoes is more important than ever, to protect people against the threat of West Nile.

Chicago Public Health Department Commissioner Dr. Bechara Choucair said the risk for West Nile Virus is significantly higher than last year, and the department has the data to back that up.

Choucair said, early this season, 76 mosquito traps were set up around Chicago. Of the 30,000 mosquitoes tested so far this year, about one in four have tested positive for West Nile, compared to about one in 100 mosquitoes testing positive last year.

“Based on the data that we collect from these traps, we actually act very decisively. So when there is a need to spray in the neighborhood, we actually do it,” he said.

That is why Lincoln Square resident Ginger Hecht called Ald. Ameya Pewar’s (47th) office to ask about spraying, after learning her neighbor Nancy Lundquist has been battling West Nile encephalitis and meningitis.

Doctors believe Lundquist was bitten in her backyard.

Hecht hoped contacting Pewar’s office would be enough.

She said she was told, “They have to check with the CDC and the city. It really isn’t up to them.”

So far, there have been six human West Nile cases in Chicago.

To put it in perspective, there were 225 cases in 2002, a year after West Nile first began showing up in the Illinois, but health officials said it’s still early, so that’s a concern, and a reason to be careful when outside.