What Happens in Encephalitis?
Encephalitis is a serious, sometimes fatal condition.
People often recover fully from the illness within a couple of weeks, but
others, especially children and older people, may have permanent problems such
seizures, memory loss, personality changes, or brain
The chance of dying from encephalitis or having permanent
problems after recovery depends on what caused the encephalitis, how severe the
illness is, how old the person is, and how quickly the illness develops.
- In cases of encephalitis that are caused by the mumps, measles,
flu, chickenpox, or mononucleosis (Epstein-Barr)
virus, most people recover within 1 to 2 weeks. Serious illness and death can
occur, but this is rare.
- In the United States, the vast majority of people recover from
encephalitis caused by mosquito-borne viruses. These types of encephalitis
include St. Louis encephalitis, La Crosse encephalitis, western equine
encephalitis, eastern equine encephalitis, and West Nile encephalitis. The
death rate ranges from 1 to 33 out of 100 people in these types of
- Herpes simplex encephalitis has a death rate of 70% to 80% when it
is not treated. But early treatment with acyclovir lowers the death rate to
about 30%.2 Among those who survive the most severe
form of this disease, many have permanent neurological problems, including
seizures, memory loss, and
In general, young children, older adults, and people who have
impaired immune systems are at the greatest risk of
serious illness, permanent neurological problems (such as seizures, memory
loss, personality changes, or
intellectual disability), or death as a result of
Centers for Disease Control and Prevention (2005). Information on arboviral encephalitides. Available online: http://www.cdc.gov/ncidod/dvbid/arbor/arbdet.htm.
Jubelt B (2010). Viral infections and postviral syndromes. In LP Rowland, TA Pedley, eds., Merritt's Neurology, 12th ed., pp. 156–185. Philadelphia: Lippincott Williams and Wilkins.
|Primary Medical Reviewer||E. Gregory Thompson, MD - Internal Medicine|
|Specialist Medical Reviewer||W. David Colby IV, MSc, MD, FRCPC - Infectious Disease|
|Last Revised||October 26, 2011|