West Nile Virus Facts


Health Department Re-Activates West Nile Virus Hotline May 1

The Lake County Health Department will re-activate the West Nile virus hotline on May 1 for county residents to report dead birds, 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 virus hotline number is: (847) 377-8300.

West Nile Virus Fact Sheet

What is West Nile encephalitis?

Encephalitis is an inflammation of the brain and can be caused by viruses and bacteria, including viruses transmitted by mosquitoes. West Nile encephalitis is an infection of the brain caused by West Nile virus.

Who gets West Nile encephalitis?

People who live in or traveled to areas where West Nile virus activity has been identified are at risk of getting West Nile encephalitis; persons older than 50 years of age have the highest risk of severe disease. Even in areas where mosquitoes do carry the virus, very few mosquitoes--much less than 1%--are infected. If the mosquito is infected, less than 1% of people who get bitten and become infected will get severely ill. The chances you will become severely ill from any one mosquito bite are extremely small.

What are the symptoms of West Nile encephalitis?

Most infections are mild, and symptoms include fever, headache, and body aches, occasionally with skin rash and swollen lymph glands. More severe infection may be marked by headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, paralysis and, rarely, death. Persons older than 50 years of age have the highest risk of severe disease.

How is West Nile virus spread?

West Nile virus is transmitted when mosquitoes become infected when they feed on infected birds. Infected mosquitoes can then transmit West Nile virus to humans and animals. West Nile virus is not transmitted from person to person. There is no evidence that a person can get the virus from handling live or dead infected birds. However, persons should avoid bare-handed contact when handling any dead animals and use gloves or double plastic bags.

Where is the West Nile virus found?

West Nile virus has been commonly found in humans and birds and other vertebrates in Africa, Eastern Europe, West Asia, and the Middle East. It had not previously been documented in the Western Hemisphere until 1999. The continued expansion of West Nile virus in the United States indicates that it is permanently established in the Western Hemisphere. West Nile encephalitis cases occur primarily in the late summer or early fall. In the southern climates where temperatures are milder, West Nile virus can be transmitted year round.

How soon after infection do symptoms appear?

Usually within 3-15 days.

How is West Nile encephalitis diagnosed?

People who live in or traveled to areas where West Nile virus activity has been identified are at risk of getting West Nile encephalitis; persons older than 50 years of age have the highest risk of severe disease. If you are determined to be at high risk and have symptoms of West Nile encephalitis, your physician will draw a blood sample and send it to a commercial or public health laboratory for confirmation. If you have any of the above symptoms, contact your health care provider.

How is West Nile encephalitis treated?

There is no specific therapy. In more severe cases, intensive supportive therapy is indicated, often involving hospitalization, intravenous fluids, airway management, respiratory support (ventilator), prevention of secondary infections (pneumonia, urinary tract, etc.), and good nursing care.

Is a woman's pregnancy at risk if she gets West Nile encephalitis?

There is no documented evidence that a pregnancy is at risk due to infection with West Nile virus.


What proportion of people with severe illness due to West Nile virus die?

First, remember that less than 1% of people who get bitten by an infected mosquito become infected and get severely ill. Case-fatality rates range from 3% to 15% among those with severe illness due to West Nile virus, and are highest among the elderly.

Is there a vaccine against West Nile encephalitis?

No, but several companies are working to develop a vaccine.

What can I do to reduce my risk of becoming infected with West Nile virus?

  • Stay indoors at dawn, dusk, and in the early evening when mosquitos are most active.
  • Wear light-colored clothing, long-sleeved shirts, long pants, socks, and a hat whenever you are outdoors (even when you are in your backyard), especially from dusk to dawn.
  • Check all window and door screens in your home to ensure there are no tears or holes for mosquitos to get through.
  • Spray clothing with repellents containing permethin or DEET since mosquitoes may bite through clothing.
    • Apply insect repellent sparingly to exposed skin. An effective repellent will contain 35% DEET (N,diethyl-meta-toluamide). DEET in high concentrations (greater than 35%) provides no additional protection.
    • Pregnant women should avoid direct exposure to mosquito repellents.
    • Children should wear a repellent with no more than 6% to 10% DEET,
    • DEET-containing repellent should not be used on children under six months of age.
    • DEET may be considered for children aged six months to two years.
    • Do not apply DEET more than three times a day to children between ages two to twelve.
    • DEET is effective for approximately four hours. Avoid prolonged or excessive use of DEET. Wash all treated skin and clothing with soap and water after returning indoors. Wash your hands before eating.
    • Avoid breathing mist from spray-type repellent. Always apply it in a well-ventilated area.Do not apply repellent inside a tent or near food.
    • Check for sensitivity by applying a repellent to a small area of skin on the arm and wait 24 hours before use.
  • Repellents may irritate the eyes and mouth, so avoid applying repellent to the hands of children.
  • Whenever you use an insecticide or insect repellent, be sure to read and follow the manufacturer's DIRECTIONS FOR USE, as printed on the product.
  • Clean up around the house:
    • Recycle/dispose of old tires, plastic containers, and paint cans;
    • Drain water regularly from rain barrels and swimming pool covers;
    • Make sure your flowerpots, window boxes, and planters drain properly;
    • Change the water in bird baths at least once a week;
    • Drill holes in the bottom of recycling and trash containers to allow water to drain;
    • Turn over all yard items to drain standing water, including wheelbarrows, canoes, toys, and plastic wading pools.
  • Note: Vitamin B and "ultrasonic" devices are NOT effective in preventing mosquito bites.

Where can I get more information about West Nile virus?

For more information, please visit the CDC web site on West Nile virus at: www.cdc.gov/ncidod/dvbid/westnile/2001spotlight.htm.

Information courtesy of

Centers for Disease Control