(STMW) — An elderly North Side woman is the first human case of West Nile virus in Illinois this summer.

The Chicago Department of Public Health reported the woman, a West Ridge neighborhood resident in her 70s, contracted the virus in July. She is now recovering at home.

Last year, 117 human cases were reported in Illinois with 11 deaths, the state Department of Public Health said in a statement.

In late May, a bird and mosquito collected in downstate Illinois were the first to test positive for West Nile this year, the department said.

West Nile is transmitted through a mosquito that has contracted the virus from feeding on an infected bird, the department said. Symptoms include fever, nausea, headache and muscle aches.

The city will spray insecticide in parts of Norwood Park, Portage Park and Dunning on Wednesday. On Thursday, parts of Humboldt Park, East Garfield Park and West Garfield Park will be sprayed, the health department said.

The areas will be targeted from dusk until about 1 a.m. both days in what will be the season’s first spraying for adult mosquitoes.

“When our mosquito traps indicate that the West Nile Virus may threaten human health in a community, we take decisive action,” CDPH Commissioner Bechara Choucair said in the statement. “Even though this summer has been cooler than average, we all must take appropriate precautions.”

The material being used to control the insects, Zenivex™, will be applied at a rate of 1.5 fluid ounces per acre, which is approved by the U.S. EPA for outdoor residential and recreational areas.

“The rapid degradation of this product makes it an excellent choice for control of West Nile virus-carrying mosquitoes,” the statement said. It will be applied by Vector Disease Control International, whose vehicles will be led by supervisors from the Department of Streets & Sanitation.

The spray is not harmful to people or pets, but “residents of targeted neighborhoods may choose to stay indoors and close their windows while spraying is underway, as an extra precaution,” the statement said.

(Source: Sun-Times Media Wire © Chicago Sun-Times 2014. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)