by EBSCO Medical Review Board


Encephalitis is swelling of the brain.

Nucleus factsheet image
Copyright © 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 prior infection in the body or a tumor.

Risk Factors

Some things that may raise the risk of encephalitis are:

  • Spending time in an area where mosquito- or tick-borne viruses are common
  • Not getting vaccinated for diseases that can cause encephalitis
  • Having a weakened immune system


Symptoms may range from mild to severe. They may be:

  • Nausea and vomiting
  • Diarrhea
  • Belly pain
  • Fever
  • Headache
  • Sleepiness
  • Loss of feeling or numbness in the body
  • Stiff neck
  • Personality changes
  • Confusion
  • 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 spine.

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


There are not many ways to treat viruses. They take time to leave the body. Most treatment will focus on supporting the body until the virus has passed.

These medicines may be given:

  • Antiviral drugs to shorten the length of the illness
  • Steroids to ease swelling in the brain
  • Diuretics 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 bite, especially in high risk areas.


Encephalitis Society 

National Institute of Neurological Disorders and Stroke 


Canadian Neurological Sciences Federation 

Health Canada 


Eastern equine encephalitis. EBSCO DynaMed website. Available at: . Updated October 1, 2019. Accessed October 18, 2019.

Herpes simplex encephalitis. EBSCO DynaMed website. Available at: . Updated August 29, 2019. Accessed October 18, 2019.

Mann AP, Grebenciucova E, et al. Anti-N-methyl-D-aspartate-receptor encephalitis: diagnosis, optimal management, and challenges. Ther Clin Risk Manag. 2014;10:517-525.

Meningitis and encephalitis information page. National Institute of Neurologic Disorders and Stroke website. Available at: Updated March 27, 2019. Accessed October 18, 2019.

Nicholas MK, Collins J, et al. Youmans Textbook of Neurological Surgery, 7th Edition. Section II: General Neurosurgery. AIDS. 2016.

Petersen LR, Brault AC, et al. West Nile virus: review of the literature. JAMA. 2013 Jul 17;310(3):308-315.

Serafini A, Lukas RV, et al. Paraneoplastic epilepsy. Epilepsy Behav. 2016;61:51-58.

West Nile virus infection. EBSCO DynaMed website. Available at: . Updated September 30, 2019. Accessed October 18, 2019.

Revision Information

  • Reviewer: EBSCO Medical Review Board Rimas Lukas, MD
  • Review Date: 09/2019
  • Update Date: 08/11/2020