CHICAGO (CBS) – The West Nile virus is back. State health officials have confirmed two human cases in the northwest suburbs.

Both cases are women in their 60s. One is from Des Plaines, the other from Rolling Meadows.

CBS 2’s Mike Parker reports officials have been spraying pesticide to kill off West Nile-carrying mosquitoes in several areas.

The Chicago Department of Public Health sprayed in the Auburn-Gresham neighborhood in the 18th Ward, as well as the neighboring 21st Ward.

Public Health Commissioner Dr. Bechara Choucair said, “when our mosquito traps indicate that the West Nile virus may threaten human health,” it’s time to take decisive action.

Tuesday and Wednesday night, city crews will spray a chemical called Zenivex, an EPA-approved killer of the northern house mosquito, which can carry West Nile.

For weeks now, scientists have been noticing that mosquitoes infected with the virus have been turning up in their traps, often bred in standing water.

Now, for the first time this year, there are people in the hospital being treated for the disease. Normally, the first human cases of West Nile aren’t seen in Illinois until August.

Dr. Linda Rae Murray, the chief medical officer for the Cook County Public Health Department said, “The only reason to hospitalize them is if they’re feeling so ill, and if they have headaches, and they’re having trouble breathing, and we want to be supportive of them in the hospital.”

Most people who contract West Nile virus don’t suffer any symptoms, but generally, people over the age of 50 are more susceptible to the flulike symptoms that can accompany the virus.

In most instances, mild cases of West Nile can cause stomach pain, diarrhea, fever, headaches, swollen glands and sore throats. In addition to older adults, children are also at high risk.

Tuesday evening in Des Plaines, as 5-year-old Anthony Schuttler practiced riding his first two wheeler, his mom, Karen, said she takes precautions with him outside, including using insect repellent.

She also said she was going to dump the water that had been standing in a kiddie pool that was standing on their driveway all week while they were on vacation.

In the park nearby, another mother worried.

“Probably what makes me even more scared is there hasn’t been that many mosquitoes, so we haven’t been as protective with the kids about it,” Josie Sopcic said.

Although the overwhelming number of West Nile cases are mild, and don’t require going to the hospital, the worst year in Illinois was 2002, when there were 884 cases across the state, and 67 deaths – 42 of them in Cook County.