A Forest Park woman has been diagnosed with the West Nile Virus, the third such case in Cook County this year. According to the county’s Department of Public Health, the illness does not appear to be severe. However, tests confirmed the presence of West Nile encephalitis, which has the potential to be life-threatening.

The 50-year-old woman, whose name public health officials declined to release, was not hospitalized. The diagnosis came July 13, but was not made public by the county office until the first week of August.

Department spokesperson Kitty Loewy said her office does not know how the woman is faring now, but if the patient was never hospitalized, then the illness is unlikely to be serious. Anyone can become infected, Loewy said, but the degree to which the virus causes harm can depend on the person’s overall health. Seniors and those suffering from a chronic illness are more susceptible.

“We are again reminded of the potentially serious health effects of mosquito-borne disease,” CCDPH Chief Operating Officer Stephen Martin, Jr., said in a written statement. “The recent dry, hot weather made us vulnerable to mosquitoes that carry the virus. Do not be complacent about protecting yourself. Wear repellent, get rid of standing water and stay indoors when mosquito activity is high.”

The West Nile Virus is transmitted by mosquitoes that have contracted the disease from an infected bird. Most people who are infected show no signs of illness, according to county health officials, though some develop flu-like symptoms. The most serious complications stemming from a West Nile Virus infection include encephalitis, an inflammation of the brain, and meningitis, which is an inflammation of the membrane around the brain and spinal cord.

The two other confirmed cases of humans becoming infected with West Nile Virus in Cook County this year occurred in Evanston and Chicago.

In 2006, 50 county residents were diagnosed, and two of those cases were fatal. One Forest Park resident in 2006 was diagnosed with West Nile encephalitis.

In 2002, when the state of Illinois was suffering from an unusually high number of West Nile cases, more than 300 people in Cook County were diagnosed, according to Department of Public Health records. Seventeen of those cases ended in death.

Though the presence of mosquitoes infected with the virus has been confirmed by tests conducted on insects trapped in Schiller Park, the county has confirmed no cases of West Nile occurring in birds. According to Loewy, 16 birds have been sent to state labs for testing, all yielding negative results.

“I can’t explain this,” Loewy said. “We’re all sort of scratching our heads and trying to figure out what that means.”