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The Evanston Health Department asks residents to inspect their yards and homes for any containers holding water for more than three days. These containers include watering cans, pet dishes, Frisbees and plastic cups.

West Nile virus is transmitted through the bite of a mosquito that has picked up the virus by feeding on an infected bird. Most people with the virus have no clinical symptoms of illness, but some may become ill three to 15 days after the bite of an infected mosquito.

Illness from West Nile is usually mild and includes fever, headache and body aches, but serious illness, such as encephalitis and meningitis, and death are possible. Persons older than 50 years of age have the highest risk of severe disease.

The best way to prevent West Nile disease or any other mosquito-borne illness is to reduce the number of mosquitoes around your home and to take personal precautions to avoid mosquito bites. Avoid being outdoors when mosquitoes are most active, especially between dusk and dawn. People should wear shoes, socks, long pants and a long-sleeved shirt outdoors and apply insect repellent that includes DEET, picaridin, oil of lemon eucalyptus or IR 3535 according to label instructions. Parents and caregivers should consult a physician before using repellents on infants.

Doors and windows should be in good repair and have tight-fitting screens. All sources of standing water that can support mosquito-breeding – water in bird baths, ponds, flowerpots, wading pools, old tires and any other receptacles – should be eliminated.