August 25, 1995

MOSQUITO-BORNE DISEASE CONFIRMED IN SOUTHERN COOK COUNTY

SPRINGFIELD, IL -- The Illinois Department of Public Health today reported that an 86-year-old southern Cook County suburban woman has a confirmed case of St. Louis encephalitis and that blood samples from two birds collected in northern Will County were positive for St. Louis encephalitis.

The woman became ill August 16 and laboratory blood tests completed Friday by the Department indicated current infection with the St. Louis encephalitis virus, which is transmitted to humans by the bite of the Culex mosquito. The woman was hospitalized and is now recovering at home.

This is only the fourth confirmed case of St. Louis encephalitis reported in Illinois in the 1990s. There was one other Illinois case this year in downstate Williamson County and two other cases occurred in 1993.

The two birds positive for St. Louis encephalitis were among 300 collected in southern Cook County and northern Will County after 11 possible cases of St. Louis encephalitis were reported in the two counties. The Department collected blood samples from the birds to determine if the virus was present in the area. Mosquitoes pick up the virus when feeding on infected birds and then pass the infection on to humans when biting.

"This case of St. Louis encephalitis and the positive bird samples confirm our earlier suspicion that the disease is present in this area," said Dr. John R. Lumpkin, state public health director. "We do not believe there is a need for undue alarm, but there is a need for increased awareness, surveillance and preventive activities."

On August 15, the Department warned residents of the two counties to take precautions to prevent and control a possible outbreak of St. Louis encephalitis.

The Culex mosquito, also known as the house mosquito, breeds in containers, such as buckets, tin cans and bird baths, that hold small pools of stagnant water, and in drainage ditches and low spots in the ground that hold water. The mosquitoes lay their eggs on small puddles of standing water and do not fly very far from where they are hatched.

Dr. Lumpkin urged residents of the two counties to drain standing water or fill in low spots in the ground that hold water, inspect screens to prevent mosquitoes from entering, use mosquito repellent when outdoors between dusk and dawn, and keep drainage ditches cleared of brush and other vegetation.

St. Louis encephalitis is a serious disease that affects the central nervous system and can cause permanent neurological damage or be fatal.

Symptoms of St. Louis encephalitis, which is most common among older adults, usually begin five to 15 days following the bite of an infected mosquito and range from a slight fever or headache to rapid onset of severe headache, high fever, muscle aches, stiffness in the back of the neck and disorientation.

Dr. Lumpkin said if two or more of the symptoms exist, a physician should be contacted immediately and the doctor informed of any recent mosquito bites.

The Culex mosquito can easily go unnoticed because it is a small insect and gentle biter.

Of the 11 possible cases of St. Louis encephalitis reported by the Department on August 15, laboratory results are still pending on seven individuals. The laboratory tests are being performed by the U.S. Centers for Disease Control and Prevention (CDC) in Fort Collins, Colorado, and the Department's Chicago laboratory.

St. Louis encephalitis has been ruled out in four of the cases that now appear to be viral meningitis, which can have symptoms similar to St. Louis encephalitis, but is transmitted through nasal or oral secretions or contact with the feces of an infected person. Viral meningitis is one of the mildest forms of meningitis and rarely results in death or serious complications.

Illinois Department of Public Health 535 West Jefferson Street Springfield, Illinois 62761 Phone 217-782-4977 Fax 217-782-3987 TTY 800-547-0466 Questions or Comments