August 4, 1995

MOSQUITO-BORN DISEASE REPORTED IN WILLIAMSON COUNTY

SPRINGFIELD, IL -- The Illinois Department of Public Health today reported a 51-year-old Williamson County resident has been diagnosed with St. Louis encephalitis, the first confirmed case in Illinois this year of a mosquito transmitted disease.

The man became ill July 4 and laboratory blood tests completed Thursday by the Department identified St. Louis encephalitis, which is transmitted to humans by the bite of the Culex mosquito. The man was hospitalized and is now recovering at home.

This is only the third case of St. Louis encephalitis reported in Illinois in the 1990s. The other two cases were in 1993.

Dr. John R. Lumpkin, state public health director, reminded Illinois residents that mosquitoes are known to transmit different types of encephalitis to humans, usually between late summer and early fall, and precautionary measures should be taken to avoid possible exposure.

"It is important for people to take precautions around their homes and eliminate places where mosquitoes breed," Dr. Lumpkin said. "Mosquitoes breed in small pools of stagnant water, such as buckets, tin cans, bird baths or low-lying areas."

Dr. Lumpkin said householders should --

• Keep yard ornaments empty of water.
• Drain or fill low spots in the ground.
• Keep drainage ditches cleared of brush and other excess vegetation.
• Inspect door and window screens to ensure they are tight-fitting and in good repair to prevent mosquitoes from entering.
• Use mosquito repellent when outdoors, applied sparingly to exposed skin or clothing, as indicated on the repellent label.

St. Louis encephalitis is spread to humans by the bite of the Culex mosquito, which can easily go unnoticed because the insect is small and a gentle biter. During the first half of the summer, Culex mosquitoes normally feed on birds, from which they can pick up the virus. In mid to late summer, the mosquitoes change their feeding habits from birds to other animals and humans. The Culex mosquito bites from dusk to dawn.

Symptoms of St. Louis encephalitis, which is most common among persons older than 55 years of age, usually begin five to 15 days following the bite of an infected mosquito. Symptoms 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. Most patients recover fully, although the disease can cause permanent neurological damage or death.

"If two or more of these symptoms exist, contact a physician immediately and inform the doctor of any recent mosquito bites," Dr. Lumpkin said.

LaCrosse (California) encephalitis is the other disease spread by a mosquito -- the tree-hole mosquito, which is distinguished by its habit of feeding during daylight hours in or near shaded or wooded areas. Symptoms of LaCrosse encephalitis, which mainly affects children, are similar to those of St. Louis encephalitis.

There were six cases of LaCrosse encephalitis reported in Illinois last year -- four in Peoria County and one each in Rock Island and Scott counties.

The Department conducts a surveillance program beginning each spring that monitors birds and mosquitoes for evidence of St. Louis encephalitis. Birds are trapped and their blood tested in about 50 counties. So far, more than 2,000 birds and hundreds of pools of mosquitoes have been tested, but all have been negative for St. Louis encephalitis.

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