Encephalitis is an inflammation (swelling and irritation) of the
brain that is usually the result of a viral infection. If not treated
immediately, encephalitis can alter brain function and become
The most common symptoms of encephalitis are fever, severe
headache, and confusion. Other symptoms may develop, such as sensitivity to
light, nausea and vomiting, stiff neck and back, and drowsiness. Sometimes
severe symptoms develop, such as seizures, tremors, personality changes, and
even coma. In general, symptoms that develop suddenly and are serious from the
start usually mean a more severe, life-threatening form of encephalitis.
Encephalitis is most often caused by a virus, such as the virus
that causes cold sores and genital herpes (herpes simplex), mumps, measles,
chickenpox, mononucleosis (Epstein-Barr virus), influenza, or German measles
(rubella). Although very rare in the United States, encephalitis may be spread
by infected mosquitoes and ticks.
Treatment usually includes hospitalization and use of the antiviral
medicine acyclovir along with supportive care for symptoms.