August 30, 1995

MOSQUITO-BORNE DISEASE REPORTED IN McDONOUGH COUNTY

SPRINGFIELD, IL -- The Illinois Department of Public Health today reported that a 14-year-old McDonough County boy has been identified as the third Illinois resident to be diagnosed this year with a mosquito transmitted disease.

The boy, who became ill August 12, is hospitalized. Tests by the Department's laboratory late last week confirmed the child had LaCrosse (California) encephalitis, which is transmitted to humans by the bite of the tree-hole mosquito.

Earlier this month two cases of St. Louis encephalitis were confirmed, one in the southern-most portion of the state in Williamson County and one in southern Cook County. St. Louis encephalitis is transmitted to humans by the bite of the Culex mosquito.

Dr. John R. Lumpkin, state public health director, said these cases underscore the fact that mosquitoes carrying encephalitis are active in Illinois and residents should take precautions to avoid possible exposure.

"Mosquitoes are known to transmit different types of encephalitis to humans, usually in the late summer and early fall. The best way to help prevent this disease is to eliminate potential mosquito breeding sites," said Dr. Lumpkin.

Mosquitoes lay eggs in water that gathers in holes in trees as well as in other containers, so residents are asked to inspect their property for discarded tires and other receptacles, such as buckets or tin cans, that hold small amounts of water.

Dr. Lumpkin also advised householders to--

• Keep yard ornaments empty of water.
• Drain or fill low spots in the ground where water accumulates.
• 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.
• Avoid exposure to mosquitoes during the times they usually bite.

The tree-hole mosquito that transmits LaCrosse encephalitis is normally active during daylight hours in wooded or heavily shaded areas. The Culex mosquito that transmits St. Louis encephalitis bites from dusk to daylight.

The tree-hole mosquito is infected with LaCrosse encephalitis virus by feeding on infected small mammals or when an infected female mosquito transmits the infection to her offspring. The Culex mosquito is infected with St. Louis encephalitis by feeding on birds that carry the virus. LaCrosse and St. Louis encephalitis are serious diseases that affect the brain. LaCrosse encephalitis occurs more often in children, while St. Louis encephalitis is more common among adults. Most patients recover fully, although some may have permanent neurological damage.

Symptoms of both diseases are similar and usually begin five to 15 days following the bite of an infected mosquito. The 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.

Dr. Lumpkin said if two or more of these symptoms appear, people should contact a physician immediately, and inform the doctor of any recent mosquito bites.

Last year in Illinois, there were six confirmed cases of LaCrosse encephalitis in Peoria, Rock Island and Scott counties. Cases of St. Louis encephalitis had not been diagnosed in Illinois since 1993, when two cases were reported in Cook and Whiteside counties.

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