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Viral Encephalitis


What is viral encephalitis?

Viral encephalitis is inflammation of the brain due to a viral infection. It may also be caused by an infection in another part of your body, which can later lead to encephalitis.

What causes viral encephalitis?

Viral encephalitis may be caused by many different viruses, including the following:

  • Mosquito-borne or tick-borne viruses: You may get viral encephalitis from a bite by an infected mosquito or tick. These include the LaCrosse, St. Louis, West Nile, and Japanese B encephalitis viruses.
  • Herpes viruses: Certain viruses may not be active in your body, then become active and cause encephalitis. Examples are viruses that cause cold sores or genital herpes, mononucleosis, chickenpox, and shingles.
  • Other viruses: Influenza, measles, mumps, and rubella (German measles) may cause encephalitis shortly after you become ill. Viral encephalitis may also be caused by the polio virus or rabies, which directly attacks the brain.

Who is at a high risk of viral encephalitis?

Viral encephalitis can affect anyone of any age. The following factors may place you at a higher risk of developing or having a more severe form of this disease:

  • You are an older adult or a very young child.
  • You spend a lot of time outdoors.
  • You have a long-term illness, such as cancer.
  • You have a weak immune system.
  • You travel to places where the mosquito-borne or tick-borne viruses are common.

What are the signs and symptoms of viral encephalitis?

  • Dizziness, headache, stiff neck, and body aches
  • Fever, nausea, and vomiting
  • Fatigue, confusion, feeling anxious, or acting or talking oddly
  • Vision changes or hearing loss
  • Back pain, weakness, trouble walking, or paralysis
  • Seizures or twitching
  • Loss of consciousness

How is viral encephalitis diagnosed?

Your healthcare provider will examine you and ask about any other health conditions you may have. This includes information about your past travels or activities. He may ask you about exposure to or contact with an infected person, or any diseases you may have had. Tell your healthcare provider if a certain disease or illness is present in your community. You may need one or more of the following tests:

  • Body fluid tests: A sample of fluid from your nose or your throat, or a sample of blood or bowel movement may be taken for tests. The results of these tests may show healthcare providers what germ is causing your illness.
  • MRI: This scan uses powerful magnets and a computer to take pictures of your brain. An MRI may show swelling and signs of inflammation in your brain. You may be given dye to help the pictures show up better. Tell the healthcare provider if you have ever had an allergic reaction to contrast dye. Do not enter the MRI room with anything metal. Metal can cause serious injury. Tell the healthcare provider if you have any metal in or on your body.
  • Lumbar puncture: A needle is inserted into your spinal canal through your back. Healthcare providers will collect a sample of the fluid to see if you have an infection. CSF may be collected and sent to a lab for tests. Healthcare providers may also drain CSF to relieve pressure and ease your headache.
  • EEG: This test is also called an electroencephalogram. Many small pads or metal discs are put on your head. Each has a wire that is hooked to a machine. This machine prints a paper tracing of brain wave activity from different parts of your brain. Healthcare providers look at the tracing to see how your brain is working.

How is viral encephalitis treated?

Treatment for encephalitis depends on the virus that caused it, and how bad the symptoms are. With treatment, such as medicine and rest, you may recover from viral encephalitis. Treatment may include more than one of the following:

  • Breathing devices: You may need a respirator and oxygen to help you breathe.
  • IV fluids: These may be given to help decrease your symptoms.
  • Medicines:
    • Antiviral medicine: These treat infections that are caused by a virus.
    • Antipyretics: This medicine is given to decrease a fever.
    • Anticonvulsants: These prevent, decrease, or stop seizures.
    • Steroids: These decrease swelling in your brain.

What are the risks of viral encephalitis?

You may become very sick from viral encephalitis. Brain swelling may cause seizures. If you do not get early treatment, you may have damage to your brain and other organs. You may have problems with hearing, seeing, talking, or learning. If left untreated, viral encephalitis may cause paralysis or be life-threatening.

How can I manage my symptoms?

  • Rest: Rest when you feel it is needed. Slowly start to do more each day. Return to your daily activities as directed.
  • Rehabilitation: After you recover, your healthcare provider may recommend physical, occupational, or speech therapy. These may help to improve movement, decrease pain, maintain daily activities, and improve your ability to eat or speak.

How can viral encephalitis be prevented?

  • Prevent bites from mosquitoes and ticks:
    • Use an insect repellant that contains DEET (active ingredient) on your clothing and exposed skin. Ask about other insect repellants to prevent bites. Use repellants with 30% DEET or less on infants who are younger than 2 months old. Follow the instructions on the label when you use an insect repellant. Do not use DEET on the hands of young children or on babies who may rub their eyes or mouth.
    • Do not go outside at sunrise and sunset, when mosquitoes are most active. If you sleep outdoors, use a mosquito net.
    • Put screens on all windows and outside doors of your house, and repair screens that have holes in them.
    • Wear long-sleeved shirts and long pants to keep your skin covered.
    • Clear dead trees and brush away from where you live. This may help to decrease ticks.
  • Decrease mosquito breeding: Get rid of places where water can stand and mosquitoes can live:
    • Do not leave containers that can collect water, such as buckets or wheelbarrows, in an uncovered or upright position.
    • Change water in animal feeders every few days.
    • Regularly check ponds, birdbaths, animal feeders, drinking troughs, and other bodies of standing water.
    • Drain or pump out standing water around your house, such as in clogged gutters and ditches.
  • Decrease exposure to viruses that cause encephalitis: Stay away from people who have colds or the flu. Wash your hands with soap and water frequently.
  • Get vaccinated: Vaccines for influenza, measles, mumps, rubella, chicken pox, and polio can help prevent an infection. A flu shot lasts for 1 year and is usually given in October and November. A vaccine against the Japanese encephalitis virus is also available. Ask which vaccinations are right for you. Make sure your pet is vaccinated against rabies. If you work with animals, or have been recently bitten, you may need a rabies shot.

Where can I find support and more information?

  • Centers for Disease Control and Prevention (CDC)
    1600 Clifton Road
    Atlanta , GA 30333
    Phone: 1- 800 - 232-4636
    Web Address:

When should I contact my healthcare provider?

  • You have a fever.
  • Your skin is itchy, swollen, or has a rash.
  • You have questions or concerns about your condition or care.

When should I seek immediate care or call 911?

  • Your symptoms get worse or come back.
  • You become confused, act differently than normal, or become harder to wake up than normal.
  • You have a bad headache, stiff neck, or trouble thinking clearly.
  • You have a seizure.
  • You have sudden trouble breathing.

Care Agreement

You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your healthcare providers to decide what care you want to receive. You always have the right to refuse treatment. The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

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