what does encephalitis come from
The exact cause of encephalitis is often unknown, but the most commonly diagnosed cause is a viral infection. Bacterial infections and noninfectious inflammatory conditions also may cause encephalitis.An infection may result in one of two conditions affecting the brain:1  Primary encephalitis occurs when a virus or other infectious agent directly infects the brain. 2  The infection may be concentrated in one area or widespread.acterial infections and noninfectious inflammatory conditions also may cause encephalitis. An infection may result in one of two conditions affecting the brain: 1  Primary encephalitis occurs when a virus or other infectious agent directly infects the brain. 2  The infection may be concentrated in one area or widespread.