There are many causes of encephalitis, and the incubation period varies from cause to cause. The incubation period for common herpesvirus I encephalitis is generally 2-21 days, with an average of 6 days. The incidence of viral encephalitis is not seasonal, there are no regional or gender differences, and it can occur at any age. The prodromal symptoms include upper respiratory tract infection such as khat symptoms, headache, fever, and cough. The duration of the disease varies from a few days to 1-2 months, and 25% of patients have a history of oral and lip herpes. The clinical manifestations are mostly mental and behavioral abnormalities and cognitive dysfunction, such as personality changes, lazy movement, and unresponsiveness. Seizures may occur in about one-third of patients, and as the disease worsens, drowsiness, lethargy, coma, or decortication tonicity may also be present. In addition to herpes I virus, there are other viruses that can cause encephalitis, such as EBV and herpes zoster virus, as well as some bacteria, fungi, and Mycobacterium tuberculosis, with different incubation periods and courses.