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Frequently Asked Questions About West Nile Virus

How is West Nile Virus Transmitted?

West Nile Virus is transmitted through the bite of mosquitos that are infected with the virus. Mosquitoes become infected with the virus when they take a blood meal from an infected bird(s). The incubation period for humans (time of infection to onset of the disease) is usually three to five days.

Am I at Risk of Contracting West Nile Encephalitis?

West Nile Virus has been found primarily in birds. When mosquitoes become infected from taking a blood meal from an infected bird, they can then pass the virus on to humans and animals such as horses through their bite. In humans, less than 1% of individuals bitten by mosquitoes become infected. Less than 1% of people who are bitten and become infected become severely ill. Those at highest risk of infection and illness are individuals of the age of 50 an over, young children, and the immunocompromised.

What Are the Symptoms on West Nile Encephalitis?

Most people infected with West Nile Virus will have no symptoms of illness. Some people may experience flu-like symptoms such as fever, headache, and body aches. In more severe cases, infection (encephalitis) may be marked by headache, high fever, stiff neck, convulsions, muscle weakness, and paralysis. In very rare instances death may occur.

What Should I Do if I Think I Am Infected?

If you think you may have West Nile Virus, seek out medical care immediately if you develop symptoms such as high fever, confusion, muscle weakness, and severe headaches. Your physician will take a medical history to determine your risk. If you are determined to be at high risk and have symptoms of West Nile Encephalitis, your provider will take a blood sample for testing.

Protecting Yourself From Mosquito Bites

  • When possible avoid times when mosquitoes are most active (dusk until dawn).
  • Avoid areas where mosquitoes may be attracted (areas of stagnant water, high grass, etc.)
  • Wear light colored clothing with tightly woven materials and when possible, wear shirts with long sleeves and pants that cover the entire leg.
  • Apply insect repellent with DEET. Read the product label and follow noted instructions.
  • Maintain window and door screens to help keep mosquitoes out of the house.

Preventing Mosquitoes From Breeding Around Your Home

There are several ways to help prevent the spread of WNV in your community. May precautions can be taken around your home including the following:

  • Drain standing water around your yard. Breeding sites can include:
    – Flower pots
    – Pet bowls
    – Clogged rain gutters
    – Swimming pool covers
    – Discarded tires
    – Containers such as buckets, improperly covered rain barrels, cans
  • Change water in bird baths at least once a week
  • Ensure flower pots/drip trays do not hold stagnant water or drain weekly
  • Fill tree rot holes and hollow stumps that hold water
  • Keep roof gutters free of leaves and other debris
  • Cover trash containers to keep out rainwater
  • Repair leaky pipes and outside faucets
  • 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 mosquito season
  • Keep grass cut short and shrubbery well-trimmed around the house to eliminate mosquito resting areas

This information was modified from brochures prepared by the Center for Disease Control (CDC) and the Illinois Department of Public Health.