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Encephalitis is swelling of the brain.

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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 before.

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 your symptoms and health history. 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.

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


The goal of treatment is to rid the body of the virus that is causing the problem. There are not many ways to treat all viruses. They take time to leave the body.

If a virus cannot be treated then treatment will focus on helping the body until the virus has passed.

These medicines may be given:

  • 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


To lower your chances of getting encephalitis:

  • Make sure your vaccinations are up to date.
  • Protect yourself from 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.
  • Serafini A, Lukas RV, et al. Paraneoplastic epilepsy. Epilepsy Behav. 2016; 61: 51-58.
  • West Nile virus infection. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/west-nile-virus-infection.