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What is encephalitis?

Encephalitis is inflammation of the brain. Inflammation can cause symptoms such as confusion, a fever, a bad headache, and a stiff neck. Sometimes it leads to symptoms like seizures and personality changes. It can also cause long-term problems, such as trouble with speech or memory.

Encephalitis is uncommon, but it can be deadly. If you think you have symptoms of encephalitis, see a doctor right away.

What causes encephalitis?

Infection with a virus is the main cause of encephalitis. Different types of viruses can cause the illness. For example, West Nile virus can cause encephalitis when a person is bitten by an infected mosquito. Another type is the herpes simplex virus, which is the same virus that causes cold sores and genital herpes. A mother who is infected with the herpes virus can also pass the virus to her baby. If this happens and the baby gets encephalitis, it is very serious.

But most people who get these types of infections don't get encephalitis.

What are the symptoms?

Symptoms of encephalitis can include:

  • Confusion.
  • A fever.
  • A headache (which can be very painful).
  • A stiff neck and back.
  • Light hurting your eyes.
  • Nausea and vomiting.
  • Lack of energy.
  • Drowsiness.

More serious symptoms include:

  • Seizures.
  • Tremors.
  • Personality changes.
  • Memory loss.
  • Hallucinations (seeing or hearing things that aren't there).

If you think that you or your child has encephalitis, call your doctor right away.

Early on, symptoms of encephalitis may be like those of meningitis. This is a serious viral or bacterial illness that causes swelling of the tissues around the brain and spinal cord.

How is encephalitis diagnosed?

Your doctor will ask questions about your past health and your symptoms. He or she will likely order tests to confirm the diagnosis. These may include:

  • Spinal fluid analysis. By doing a lumbar puncture (also called a spinal tap), your doctor can check the spinal fluid for an increase in white blood cells and protein.
  • Imaging tests. An MRI or CT scan, which takes pictures of the inside of your body, may show bleeding, swelling, or other changes in the brain. See a picture of a brain with encephalitis.
  • Electroencephalogram (EEG). This test can measure the electrical signals in the brain. It may show a change related to the illness.
  • Blood tests. These tests can show what type of virus is causing encephalitis.

How is it treated?

If you have encephalitis, you will need to be treated in a hospital. Your treatment will depend on your symptoms and the cause of your illness. You may be treated right away with an antiviral medicine, such as acyclovir. Antiviral medicine may make symptoms less severe, especially if you get the medicine right away. If the doctor thinks that your symptoms are caused by bacteria, rather than by a virus, he or she may treat you with antibiotics.

You will also get care to ease your symptoms and allow your body to heal on its own. This is called supportive care. You may take medicines to reduce pain and fever or to stop seizures. In some cases, you may need a machine called a ventilator to help you breathe.

After you are out of the hospital, it may take several weeks, months, or even longer to fully recover from your symptoms. You can take care of yourself by eating well and getting plenty of rest. Follow your doctor's instructions on how much fluid to drink. If your doctor says it's okay, you can take nonprescription pain relievers for headaches. These include acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs) like naproxen, ibuprofen, or aspirin. Do not give aspirin to anyone younger than 20 because of the risk of Reye syndrome.

Some people have long-term problems. If you have muscle weakness or problems with coordination, you may need physical therapy. If you have speech or memory loss, you may need speech therapy or occupational therapy.

Can encephalitis be prevented?

Your chance of getting encephalitis is low. But there are things you can do to reduce your chances even more.

  • Make sure that you and your children get shots (vaccines) against measles, mumps, rubella, chickenpox, and the flu.
  • Avoid areas where there has been an outbreak of viral encephalitis. If you can't avoid these areas, prevent mosquito bites with these tips:
    • Stay indoors at dawn, at dusk, and in the early evening, when mosquitoes are most active.
    • Wear long-sleeved shirts and long pants whenever you are outdoors and are likely to be where mosquitoes are.
    • Avoid wearing floral fragrances from perfumes, soaps, hair care products, and lotions. These may attract mosquitoes.
    • Use insect repellent with DEET (N,N-diethyl-meta-toluamide). The repellent is available in varying strengths up to 100%. In young children, use a preparation containing less than 24% strength, because too much of the chemical can be absorbed through the skin.
    • Spray clothing with an insect repellent containing permethrin or DEET, because mosquitoes may bite through thin clothing. DEET can damage plastic items, such as watch crystals or eyeglass frames, and some synthetic fabrics. You also can use natural products such as soybean-based Bite Blocker.
    • Avoid applying repellent to the hands of children. Repellents may irritate the eyes and mouth.
    • Whenever you use an insecticide or insect repellent, be sure to read and follow the directions for use.
    • Do not keep open containers of water near your house. Standing water is a breeding place for mosquitoes.
  • If you are taking a long trip to the Far East or to central or eastern Europe, talk to your doctor about getting vaccinated against certain types of mosquito- or tick-borne encephalitis. For example, there is a vaccine for Japanese encephalitis. Getting vaccinated is especially important if you are going to a rural area.

Other Places To Get Help


National Institute of Neurological Disorders and Stroke
NIH Neurological Institute
P.O. Box 5801
Bethesda, MD  20824
Phone: 1-800-352-9424
Phone: (301) 496-5751
TDD: (301) 468-5981
Web Address: www.ninds.nih.gov

The National Institute of Neurological Disorders and Stroke (NINDS), a part of the National Institutes of Health, is the leading U.S. federal government agency supporting research on brain and nervous system disorders. It provides the public with educational materials and information about these disorders.

Centers for Disease Control and Prevention (CDC): Division of Vector Borne Diseases (DVBID)
3150 Rampart Road
Fort Collins, CO  80521
Phone: 1-800-CDC-INFO (1-800-232-4636)
Fax: (770) 488-4760
TDD: 1-888-232-6348
Email: cdcinfo@cdc.gov
Web Address: http://cdc.gov/ncezid/dvbd/

The Division of Vector-Borne Infectious Diseases is a national and international reference center for vector-borne viral and bacterial diseases. The mission of the division is to develop and maintain effective surveillance for vector-borne infectious diseases; conduct field and laboratory research and epidemic aid investigations; develop improved methods and strategies for disease diagnosis, surveillance, prevention, and control; and provide information and technical expertise.

KidsHealth for Parents, Children, and Teens
Nemours Home Office
10140 Centurion Parkway
Jacksonville, FL 32256
Phone: (904) 697-4100
Web Address: www.kidshealth.org

This website is sponsored by the Nemours Foundation. It has a wide range of information about children's health—from allergies and diseases to normal growth and development (birth to adolescence). This website offers separate areas for kids, teens, and parents, each providing age-appropriate information that the child or parent can understand. You can sign up to get weekly emails about your area of interest.


Other Works Consulted

  • Drugs for non-HIV viral infections (2010). Treatment Guidelines From The Medical Letter, 8(98): 71–82.
  • Gilden DH (2008). Acute viral central nervous system diseases. In DC Dale, DD Federman, eds., ACP Medicine, section 11, chap. 16. Hamilton, ON: BC Decker.
  • Tunkel AR, et al. (2008). The management of encephalitis: Clinical practice guidelines by the Infectious Diseases Society of America. Clinical Infectious Diseases, 47(3): 303–327.


ByHealthwise Staff
Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine
Specialist Medical ReviewerW. David Colby IV, MSc, MD, FRCPC - Infectious Disease
Last RevisedOctober 26, 2011

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