Mosquitoes Test Positive for West Nile Virus in Lake County

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For Immediate Release
Date: June 30, 2016
Contact: Leslie Piotrowski
(847) 377-8055

Mosquitoes Test Positive for West Nile Virus in Lake County

A mosquito pool (or batch of mosquitoes) sampled June 23 in Highland Park has tested positive for West Nile virus. The mosquito pool is the first confirmed indicator of the disease’s presence in Lake County in 2016.  In 2015, five human cases of West Nile virus were reported in Lake County. In addition, 68 pools or batches of mosquitoes and one bird tested positive for the virus.

“This is the time of year when we begin to see mosquito pools testing positive for West Nile virus,” said Mark Pfister, the Health Department’s interim Executive Director. “Now that hot summer weather is finally here, it is especially important to protect yourself against mosquito bites by following the four D’s – Drain: regularly empty water from outdoor containers; Dress: cover skin by wearing long sleeved shirts and pants; Dawn and Dusk: stay indoors during early evening and morning hours; and Defend: use insect repellent that contains DEET.”

The Health Department maintains a West Nile virus hotline for county residents to report areas of stagnant water (which are conducive for mosquito breeding), or to obtain more information on the signs and symptoms of West Nile encephalitis. The West Nile hotline number is: (847) 377-8300. Information can also be found at:

Recommendations to prevent mosquito breeding include:

  • Discard old tires, buckets, drums or any water holding containers. Poke holes in tires used as bumpers on docks
  • Keep roof gutters and downspouts clear of debris
  • Keep trash containers covered
  • Empty plastic wading pools at least once a week and store indoors when not in use
  • Drain unused swimming pools
  • Fill in tree rot holes and hollow stumps that hold water
  • Change the water in bird baths and plant urns at least once a week
  • Store boats upside down or drain rainwater weekly

Recommendations to prevent mosquito bites include:

  • Whenever possible, limit outdoor activity at dusk
  • Wear light-colored clothing that minimizes exposed skin and provides some protection from mosquito bites
  • Make sure door and window screens fit tightly and that all holes are repaired
  • Apply insect repellent that includes DEET, picaridin, oil of lemon eucalyptus or IR 3535 according to label instructions. Consult a physician before using repellents on infants.

 While most people infected with WNV have no symptoms of illness, some may become ill, usually three to 15 days after the bite of an infected mosquito. In some individuals, particularly the elderly, the virus can cause muscle weakness, inflammation of the brain (encephalitis), stiff neck, stupor, disorientation, tremors, convulsions, paralysis, coma or death.

The Health Department conducts a multi-faceted mosquito surveillance program in Lake County. Beginning in late spring and continuing into the autumn, a series of traps are set around the county, including within the Lake County Forest Preserves. At each site a pool, or batch, of mosquitoes is tested weekly for West Nile virus. Areas of stagnant water are also investigated throughout the season for the presence of mosquito larvae, specifically from the Culex mosquito which is the primary carrier of West Nile in Illinois. Finally, the locations of dead birds are monitored to assist in the assessment of potential West Nile virus activity. The Health Department works closely with the municipalities, townships, and the Lake County Forest Preserve District in monitoring the mosquitoes that may pose a public health threat.

It is also important to remember that other mosquito species carry disease such as Zika Virus, Dengue and Chikungunya, in areas outside northeast Illinois. People vacationing in areas with ongoing disease transmission from mosquitoes should protect themselves from any mosquito bites. 

Information about WNV can be found on the Department’s Website at:

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Lake County Health Department
3010 Grand Avenue
Waukegan, Illinois 60085
(847) 377-8000