West Nile Virus 

West Nile Virus - mosquito imageThe Problem: Mosquitoes transmit serious and sometimes fatal diseases, such as the West Nile Virus, to humans, horses, and their pets.

About the West Nile Virus: The West Nile Virus (WNV) is a mosquito-borne virus that is commonly found in Africa, West Asia, and the Middle East, and in recent years has been found in the United States. The onset of symptoms is 3 to 14 days after being bitten by an infected mosquito. Most people infected with the WNV experience few if any symptoms and recover completely after a few days. Mild symptoms include a fever, headache, body aches, occasionally with a skin rash on the trunk of the body, and swollen lymph glands. Although rare, some people experience severe infection (West Nile encephalitis or meningitis) and the symptoms include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis.

Persons over about 55 or with pre-existing health conditions are more likely to develop severe illness. Symptoms of severe disease may last several weeks, although neurological effects may be permanent.

Transmission: Mosquitoes become infected with the WNV when they feed on infected birds and can then transmit the virus to humans and animals while biting to take blood. The WNV is NOT transmitted from person-to-person. Other possible transmission routes of the virus are being studied. In areas where the virus is circulating, very few mosquitoes are infected. Even if the mosquito is infected there is a very low chance that people who get bitten and become infected will get severely ill. The chances you will become severely ill from one mosquito bite are extremely small.

West Nile Virus - transmission

Reduce Mosquito Breeding Sites From Around Your Home: The carrier of WNV, the Culex mosquito flies only 1-2 miles. Every 7-10 days, a new hatch of mosquitoes can be produced in an area of stagnant water...remove standing water to reduce mosquito populations! Eliminating the following stagnant water sites around homes will reduce the risk of disease:

  • Discard old tires, tin cans, buckets, bottles, and other water-holding containers.
  • Fill in or drain any low places in the yard, holes in trees, or hollow stumps.
  • Keep gutters, drains, and ditches clean so that water will drain properly. Repair leaky pipes and faucets.
  • Cover trash containers to keep out rainwater.
  • Empty plastic wading pools at least once a week and store indoors when not in use.
  • Change the water in birdbaths and plant pots at least once a week and stock ornamental ponds with mosquito eating fish or use mosquito larva control products.
  • Keep grass short and shrubbery well trimmed around the house.
  • Report mosquito-breeding sites to your local mosquito control agency.

West Nile Virus - crowCrows, Blue Jays, and Raptors: The DuPage County Health Department (DPCHD) may collect crows and blue jays for its WNV surveillance program. These birds are very sensitive to WNV and they can indicate the presence of WNV in an area. Crows and blue jays will continue to be collected and tested for WNV until the DPCHD receives enough evidence that the WNV is throughout the county. Once the DPCHD receives several positive birds for WNV, it may suspend its WNV bird surveillance program.

If a dead bird is found, use rubber gloves when picking up birds or use plastic bags, double bag the bird, and then discard the bird in the trash.

If a sick or injured wild bird (other than a crow or blue jay) or animal is found, contact the Willowbrook Wildlife Center at 630-942-6200.

Mosquito Treatment Questions: If you have questions about the frequency of mosquito treatment in your area, contact your local municipality or Clarke Environmental Mosquito Control at 800-942-2555.

Protect Yourself From Mosquito Bites: Most mosquitoes bite at dusk or at night, but some kinds will bite during the day. Almost all mosquitoes will try to bite you if you enter an area where they are resting.

  • When possible, avoid places and times when mosquitoes bite.
  • Wear light-colored protective clothing that covers your arms and legs. Tuck the legs of pants into boots or socks and keep collars buttoned.
  • Make sure door and window screens fit tightly, and repair any holes.
  • Use mosquito netting when sleeping outdoors and around small babies for protection at all times.
  • Use mosquito repellents with about 30% DEET (about 10% DEET for children age 2-12). Adults should supervise repellent use by children. Do not use any repellents on children under 2 years of age without consulting your doctor. Apply them to clothes whenever possible and apply sparingly to skin if the label permits. Wash repellent off daily. DO NOT apply over cuts or irritated skin or near the eyes, lips or nose.
  • DO NOT rely on insect light electrocuters ("bug zappers"). They do little to reduce biting mosquitoes in an area.

More information about West Nile Virus may be found at:

IDPH West Nile Virus in Illinois
CDC West Nile Virus Home Page