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La Crosse Encephalitis

What is La Crosse?

La Crosse is a viral infection that can cause inflammation of the brain (encephalitis).

How do people get La Crosse encephalitis?

La Crosse is transmitted by infected mosquitoes that can bite during the day.  La Crosse virus can NOT be spread from person-to-person.

Where is La Crosse encephalitis found?

La Crosse encephalitis is most common in the areas of the upper Midwestern United States and in the Appalachian region (West Virginia, North Carolina, Tennessee, Virginia).

Who can get La Crosse encephalitis?

Anyone who is bitten by a La Crosse infected mosquito can get La Crosse encephalitis.  Children 16 years of age and under are most susceptible to La Crosse disease.

What are the symptoms?

Mild illness may include headache, fever, nausea, vomiting and tiredness.  Children with severe disease may progress to severe headache, nausea, stiff neck, muscle aches, drowsiness, disorientation, and seizures.  Fatality is rare but does occur occasionally.

How is La Crosse encephalitis diagnosed?

Blood samples must be collected at onset of illness and again in two to four weeks after illness resolves to confirm La Crosse encephalitis.  Contact your physician for details.

How is it treated?

There is no specific treatment for La Crosse infection.  More severe illnesses are treated by supportive therapy which may include hospitalization, respiratory support, IV fluids, prevention of other infections and good medical care.

What should I do if I think a family member has La Crosse?

Contact your family physician immediately.

How can you prevent La Crosse encephalitis?

Protect yourself from mosquito bites

  1. Apply a mosquito repellent to exposed skin when outdoors.  The most effective repellents contain DEET (N, N-diethyl-metatoulamide).  Follow all label directions carefully.  
  2. Non-DEET products provide some protection from mosquito bites but may not last as long as DEET products.  Persons who are concerned about using products containing DEET may wish to consult their health care provider for advice.
  3. Children over 10 months of age may use products that contain 10 percent DEET or less.  Protect infants less than 10 months of age by placing mosquito netting over infant carriers when outdoors.
  4. Spray clothing with repellents containing Permethrin or DEET since mosquitoes can bite through thin clothing.  
  5. DO NOT apply repellents containing Permethrin on exposed skin.

Get rid of standing water around your home

  1. Eliminate mosquito breeding habitats by draining standing water in toys, flower pots, etc.  Remove used tires and unclog gutters.
  2. Flush bird baths every two to three days.
  3. Clean and chlorinate swimming pools.
  4. Install or repair damaged or torn window and door screens to prevent mosquitoes from entering the home.
  5. Decorative ponds can be stocked with Gambusia minnows that will eat immature mosquitoes.

Healthcare providers, laboratories, and public health professionals can find more information about this disease and a variety of others at the Tennessee Department of Health Reportable Diseases and Events home page