Aug. 20,1998

SPRINGFIELD, IL — The Illinois Department of Public Health again wants to remind citizens, as they engage in outdoor activities during the final weeks of summer, to protect themselves from mosquito bites. "Mosquitoes can transmit a number of diseases," said Dr. John R. Lumpkin, state public health director. "If you are going to be outdoors – especially when mosquitoes are most active – you need to take appropriate precautions to avoid being bitten."

Precautions are particularly important in the northeastern part of the state where the Department's early warning system for possible mosquito-borne disease activity has detected recent evidence of encephalitis viruses.

Four birds collected in June and July in Cook and DuPage counties have been found to have antibodies to eastern equine encephalitis (EEE). Three of the birds were collected in central and southern Cook County and the other was collected in southern DuPage County. Also, two birds positive for St. Louis encephalitis (SLE) were collected in central and southern Cook County. Samples from additional birds collected in these areas are undergoing laboratory testing by the U.S. Centers for Disease Control and Prevention (CDC) to further assess the risk of human illness. The Department is continuing to collect and test birds. No human cases of illness from either virus have yet been reported.

"These positive samples indicate that virus is circulating in wild birds and that encephalitis may become a problem in the area," said Dr. Lumpkin. "We do not believe this information indicates a need for alarm, but persons – particularly those living in central and southern Cook, southern DuPage and northern Will counties – should increase their awareness, surveillance and prevention activities."

Two types of encephalitis are most common in Illinois: St. Louis encephalitis, which commonly strikes older adults, and LaCrosse encephalitis, which generally affects children. Both illnesses are characterized by similar symptoms, which 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. Symptoms usually appear five to 15 days following the bite of an infected mosquito.

EEE, which is carried by marshland and wetland mosquitoes, is primarily a disease of horses. Although the virus can infect humans, cases are extremely rare – only about five are reported annually in the United States.

Dr. Lumpkin emphasized that personal protection is essential. Such measures are most important when people participate in outdoor activities during times when mosquitoes are active.

• Be sure door and window screens are tight-fitting and in good repair.
• Wear appropriate clothing. Long-sleeved tops and long pants made of tightly woven materials keep mosquitoes away from the skin. Be sure, too, that your clothing is light colored. Keep trouser legs tucked into boots or socks.
• Use mosquito netting when sleeping outdoors or in an unscreened structure.
• Check to see that your mosquito repellent contains DEET, a chemical commonly found in these products. Generally, repellents with about 30 percent DEET work best for adults; use lower concentrations for children. When outdoors, apply repellent sparingly to exposed skin or clothing, as indicated on the product's label.

Another important preventive measure is to eliminate the places where mosquitoes breed. Here are some suggestions:

• Remove or empty water in old tires, tin cans, buckets, drums, bottles or other places where mosquitoes might breed. Be sure to check clogged gutters and flat roofs that may have poor drainage. Make sure cisterns, cesspools, fire barrels, rain barrels and trash containers are covered tightly with a lid or with 16-mesh screen.
• Empty plastic wading pools at least once a week and store indoors when not in use. Unused swimming pools should be drained and kept dry during the mosquito season.
• Change the water in bird baths and plant pots or drip trays at least once each week.
• Store boats covered or upside down, or remove rainwater weekly.
• Empty your pet's water bowl daily.
• Level the ground around your home so water can run off and not collect in low spots. Fill in holes or depressions near your home that accumulate water.
• Fill in tree rot holes and hollow stumps that hold water.
• If you have an ornamental water garden, stock it with mosquito-eating fish such as minnows, "mosquito fish," goldfish or guppies.
• Keep weeds and grass cut short; adult mosquitoes look for these shady places to rest during the hot daylight hours.
• Use a flyswatter or household spray to kill mosquitoes, flies or other insects in buildings.
• Some mosquito control methods are not very effective. Bug zappers are not effective in controlling biting mosquitoes. Various birds and bats will eat mosquitoes, but there is little scientific evidence that this reduces mosquitoes around homes.
• Community-wide mosquito abatement programs can be quite effective if they are conducted as integrated pest management programs. The control program should emphasize monitoring and draining or treating areas where mosquitoes breed – such as occasionally flooded marshes, river backwater areas, swamps and other low-lying areas – treating catch basins and removing water-filled containers like old tires.

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