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Viral Encephalitis

Medically reviewed by Last updated on Aug 31, 2022.

What is viral encephalitis?

Viral encephalitis is inflammation of the brain due to a viral infection.

What causes viral encephalitis?

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

  • Mosquito-borne or tick-borne viruses, such as the LaCrosse, St. Louis, West Nile, and Japanese B encephalitis viruses
  • Viruses that cause cold sores or genital herpes, mononucleosis, chickenpox, and shingles that stay in your body and become active later
  • Influenza, measles, mumps, and rubella (German measles) viruses
  • Polio or rabies viruses

What increases my risk for viral encephalitis?

Viral encephalitis can affect anyone of any age, but elderly persons and infants are at highest risk. Any of the following can increase your risk:

  • Activities such as camping or hiking that keep you outdoors
  • A chronic illness, such as cancer
  • A weak immune system
  • Travel to an area where mosquito-borne or tick-borne viruses are common
  • Contact with animals or insects that viruses can start in, such as bats
  • Not getting vaccines that can prevent some viral infections

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. Your provider may ask you about exposure to or contact with a person infected with a virus. You may need any of the following tests:

  • Body fluid tests may include a sample of fluid from your nose or your throat, blood, or bowel movement. The results of these tests may show healthcare providers which germ is causing your illness.
  • MRI pictures may show swelling and signs of inflammation in your brain. You may be given contrast liquid to help swelling or inflammation show up better in the pictures. Tell the healthcare provider if you have ever had an allergic reaction to contrast liquid. 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.
  • A lumbar puncture may be used to collect a sample of cerebrospinal fluid (CSF) to see if you have an infection. A needle is inserted into your spinal canal through your back. CSF may also be drained to relieve pressure and ease a headache.
  • An EEG is used to check how your brain is working. Brain wave activity is recorded from different parts of your brain.

How is viral encephalitis treated?

Treatment depends on the virus, and on your symptoms. With treatment, such as medicine and rest, you may recover from viral encephalitis. Treatment may include any of the following:

  • Breathing devices such as a respirator and oxygen help you breathe.
  • IV fluids may be given to help decrease your symptoms.
  • Medicines may be given to treat an infection caused by a virus. You may also need medicine to prevent or treat a fever, seizures, or swelling in your brain.

Treatment options

The following list of medications are in some way related to or used in the treatment of this condition.

How can I manage my symptoms?

  • Rest when you feel it is needed. Slowly start to do more each day. Return to your daily activities as directed.
  • Physical, occupational, or speech therapy may be recommended after you recover. 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:
    • Wear long-sleeved shirts and long pants to keep your skin covered any time you are outdoors.
    • Use an insect repellant that contains DEET (active ingredient) on your clothing and exposed skin. 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.
    • Clear dead trees and brush away from where you live to decrease ticks.
    • 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.
    • Do not leave containers that can collect water in an uncovered or upright position. Mosquitos breed in standing water. Regularly check 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.
  • Remove ticks immediately. If a tick is biting, you will only see its body. The head will be buried in your skin. Use tweezers to remove the tick, if possible. Hold the tick with the tweezers as close to your skin as you can get. Pull the tick up and out of your skin. Do not pull hard or twist the tick. If you pull too quickly or too hard, you will pull the body off but leave the head in place. Instead, use firm, even pressure to pull the tick out. Flush the tick down the toilet if you can. If not, seal it in a plastic bag or wrap it in tape before you put it in the trash.
  • Wash your hands often. This helps prevent the spread of viruses that can lead to encephalitis. Wash your hands several times each day. Wash after you use the bathroom, change a child's diaper, and before you prepare or eat food. Use soap and water every time. Rub your soapy hands together, lacing your fingers. Use the fingers of one hand to scrub under the nails of the other hand. Wash for at least 20 seconds. Rinse with warm, running water for several seconds. Then dry your hands with a clean towel or paper towel. Use germ-killing gel if soap and water are not available. Do not touch your eyes, nose, or mouth without washing your hands first.
  • Ask about vaccines you may need. Vaccines for influenza, measles, mumps, rubella, chicken pox, and polio can help prevent an infection. Get a flu vaccine each year as soon as recommended, usually starting in September or October. 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 the rabies vaccine.

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:

Call your local emergency number (911 in the US) if:

  • You have a seizure.
  • You have sudden trouble breathing.

When should I seek immediate care?

  • 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.

When should I call my doctor?

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

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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Further information

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