Encephalitis is inflammation of the brain. The inflammation may involve the whole brain or just parts of the brain. Encephalitis may just occur in individuals (sporadic) or may affect many people in a particular area (epidemic).
Encephalitis is most often caused by a viral infection. In the United States, the most common cause of sporadic encephalitis is the herpes simplex virus (HSV). Epidemic causes of encephalitis are usually mosquito- or tick-borne viruses.
The most common viruses that cause encephalitis include:
Not all encephalitis is caused by a virus. Some may be due to an overreaction of the immune system.
Factors that may increase your chance of encephalitis include:
Newborns of mothers who have genital herpes simplex are at risk for herpes simplex encephalitis
The symptoms may range from mild to severe. Severe symptoms can include permanent neurological damage. Encephalitis can also lead to death.
Milder symptoms include:
More severe symptoms may include:
You will be asked about your symptoms and medical history. A physical exam will be done.
Your bodily fluids may be tested. This can be done with:
Images may be taken of your head. This can be done with:
Your brain's electrical activity may be tested. This can be done with an electroencephalogram (EEG).
Treatment is mostly supportive. It may include:
To help reduce your chance of getting encephalitis, take these steps:
The Encephalitis Society
National Institute of Neurological Disorders and Stroke
Canadian Neurological Sciences Federation
Herpes simplex encephalitis. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated February 1, 2013. Accessed September 23, 2014.
California encephalitis. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated February 21, 2013. Accessed September 23, 2014.
Eastern equine encephalitis. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated June 23, 2014. Accessed September 23, 2014.
NINDS meningitis and encephalitis information page. National Institute of Neurologic Disorders and Stroke website. Available at: http://www.ninds.nih.gov/disorders/encephalitis_meningitis/encephalitis_meningitis.htm. Updated April 16, 2014. Accessed September 23, 2014.
West Nile virus infection. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated June 23, 2014. Accessed September 23, 2014.
10/1/2013 DynaMed Systematic Literature Surveillance http://www.ebscohost.com/dynamed. Reimer LJ, Thomsen EK, Tisch DJ, et al. Insecticidal bed nets and filariasis transmission in Papua New Guinea. N Eng J Med. 2013 Aug 22; 369(8):745-53.
Last reviewed August 2014 by Rimas Lukas, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.