The diagnosis of encephalitis is mainly based on clinical manifestations and auxiliary examinations. Clinical manifestations include rapid onset and severe illness, mostly with a history of cold, diarrhea, herpes of the mouth and lips, high fever, headache, vomiting, convulsions, and even coma at the onset, and some have abnormal mental behavior, such as babbling and attacking others. Older patients may present with apathy, reduced speech, and dull expression. Important ancillary tests include the following: 1. Lumbar puncture suggests increased cerebrospinal fluid pressure, and cerebrospinal fluid laboratory tests show elevated red blood cells and white blood cells and elevated protein. The pathogenic examination of cerebrospinal fluid includes viral infection, etc. 2. cranial magnetic resonance or cranial CT examination suggests focal hemorrhagic softening foci in the brain, commonly in the frontal and temporal lobes. 3. electroencephalography reveals diffuse high-amplitude slow waves, with more pronounced abnormalities in the temporal and frontal regions on the side of the lesion. 4. routine blood tests suggest varying degrees of elevated white blood cells.