Mosquito-Borne Diseases

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Mosquito-borne diseases are spread to people and animals by the bite of an infected mosquito. The viruses that cause these diseases include West Nile virus (WNV), eastern equine encephalomyelitis (EEE), St. Louis encephalitis (SLE), La Crosse encephalitis, and western equine encephalomyelitis (WEE). These infections are not contagious (“catching”). Outbreaks are most common in warm climates. In cooler places, mosquitoes start biting in the spring when the temperature at night reaches 60 degrees and continue until the first hard frost in the fall. Warm spells in the winter can also cause mosquitoes to become active.

Signs and Symptoms

Most children, who get one of these viruses, have few signs or symptoms. Common signs are mild fever, headache, body aches, nausea, vomiting and a rash. However, severe illness can occur if the virus affects the membranes of the brain and spinal cord (meningitis) or the brain itself (encephalitis).

Call your child’s doctor right away if your child has any of these symptoms:

  • Sudden high fever
  • Severe headache
  • Stiff neck
  • Confusion
  • Muscle jerks, tremors, seizure
  • Nausea or vomiting
applying insect repellent


Since there is no vaccine or medicine to protect against these diseases, prevention is very important. In severe cases, a hospital stay may be needed.

Preventing Mosquito-Borne Diseases

Use insect repellant with 30% DEET. (Do not use DEET on children younger than 2 months.) Do not use a product that combines repellant with sunscreen (Picture 1).

To use:

  1. Apply to your hands first then rub it on your child. Do not apply over cuts or wounds.
  2. Avoid the child’s eyes and mouth. Use lightly on the ears.
  3. Do not apply under clothing. If repellant gets on clothing, wash the clothes before they are worn again.
  4. Bathe your child with soap and water and rinse with clear water to remove repellant before he or she goes to bed.
  5. Keep repellent out of the reach of children and pets.

Other ways to prevent mosquito-borne diseases:

  • Use screens in windows to keep mosquitoes out.
  • Empty any standing water from flowerpots, wading pools, buckets and other sources because these are breeding grounds for mosquitoes.
  • Keep children indoors at dusk and at dawn. Mosquitoes are most active at these times.

Mosquito-Borne Diseases (PDF)

HH-I-297 2/09 Copyright 2009, Nationwide Children’s Hospital