Encephalitis can generally be divided into three main categories according to the cause: first, viral encephalitis; second, bacterial encephalitis. Acute viral encephalitis is a condition that develops rapidly, with neurological symptoms peaking within a short period of time, while chronic viral encephalitis is a condition that starts slowly over a long period of time, such as months or even years, before symptoms gradually manifest. The most common causes of viral encephalitis are epidemic B encephalitis, encephalitis caused by respiratory viruses such as measles encephalitis, and sporadic viral encephalitis such as herpes simplex encephalitis, herpes zoster encephalitis, etc. Bacterial encephalitis is an inflammation caused by bacterial infection in the skull and is usually diagnosed by lumbar puncture of the cerebral fluid. The third category, autoimmune encephalitis, is encephalitis caused by an autoantigenic antibody response.