CHICAGO (CBS) — With the first reported human cases of the West Nile virus in the Chicago area, local health departments are taking no chances.

As CBS 2’s Susanna Song reports, the Chicago Department of Public Health on Wednesday night will spray in the Forest Glen neighborhood on the city’s Northwest Side. Crews will also be spraying in Beverly, North Park and Austin.

On Wednesday night, they were out in the Auburn-Gresham neighborhood laying down a chemical called Zenivex, a substance approved by the U.S. Environmental Protection Agency to exterminate 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 told CBS 2’s Mike Parker, “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.

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.

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