Twenty four other human cases have been reported in the state in 2020, according to the IDPH.
The Chicagoan became ill in mid-September and tested positive for West Nile virus.
"Although we are already into fall, West Nile virus remains a risk until the first hard frost," IDPH Director Dr. Ngozi Ezike said. "It's important for everyone to continue taking precautions such as using insect repellent, wearing long sleeve shirts and pants and staying indoors between dusk and dawn."
Last year, IDPH reported 28 human cases, although human cases are underreported, including one death. In 2019, 46 counties in Illinois reported a West Nile virus positive mosquito batch, bird, horse or human case.
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West Nile virus is transmitted through the bite of a mosquito. Common symptoms include fever, nausea, headache and muscle aches. Symptoms may last from a few days to a few weeks. However, four out of five people infected with West Nile virus will not show any symptoms. In rare cases, severe illness including meningitis or encephalitis, or even death, can occur. People older than 50 and immunocompromised individuals are at higher risk for severe illness.
State health officials ask that Illinois residents take the following steps:
Additional information about West Nile virus can be found on the IDPH website.