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  • Cynthia M. Johnson, MA
Publication Type:




Encephalitis is swelling of the brain.


Nucleus factsheet imagehttp://services.epnet.com/getimage.aspx?imageiid=73007300si2094.jpgsi2094.jpgNULLjpgsi2094.jpgNULL\\hgfiler01a\intellect\images\si2094.jpgNULL15NULL2008-11-072663907300_21335Copyright © Nucleus Medical Media, Inc.


Encephalitis can often be caused by an infection. Some common ones are:

It can also be caused by a problem with the immune system, such as a tumor or having an infection in the body outside of the central nervous system.

Risk Factors

Some things that may raise the risk of encephalitis are:

  • Spending time in places where viruses carried by mosquitoes or ticks are common
  • Not getting vaccinated for diseases that can cause encephalitis
  • Having a weakened immune system


A person with encephalitis may have:

  • Nausea and vomiting
  • Diarrhea or belly pain
  • Fever
  • Stiff neck or headache
  • Sleepiness
  • Loss of feeling or numbness in the body
  • Confusion or personality changes
  • Seizures


The doctor will ask about symptoms and past health. A physical exam will be done.

Blood tests will be done to look for signs of infection. A lumbar puncture may be done to test the fluid around the brain and spine.

Pictures may be taken of the brain to look for changes. This can be done with:


The underlying cause of the encephalitis will need to be treated. A team of specialists may be needed.

Medicines may be given, such as:

  • Antiviral drugs to make the illness last a shorter time
  • Steroids to ease swelling in the brain
  • Medicines to ease pressure in the head
  • Anti-seizure medicine to prevent and treat seizures

If a virus cannot be treated, then the goal may be to manage symptoms until the virus has passed on its own.


Encephalitis may be prevented by:

  • Staying up to date with vaccinations
  • Taking steps to avoid mosquito and tick bites, especially in high risk areas.




  • Eastern equine encephalitis. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/eastern-equine-encephalitis.
  • Herpes simplex encephalitis. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/herpes-simplex-encephalitis.
  • Meningitis and encephalitis information page. National Institute of Neurologic Disorders and Stroke website. Available at: https://www.ninds.nih.gov/Disorders/All-Disorders/Meningitis-and-Encephalitis-Information-Page.
  • Grebenciucova E, Collins J, et al. Youmans Textbook of Neurological Surgery, 8th Edition. Neurologic manifestations of human immunodeficiency virus infection and acquired immunodeficiency syndrome. Elsevier. 2022.
  • West Nile virus infection. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/west-nile-virus-infection.


  • David L. Horn, MD, FACP
Last Updated:

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.