Fever and headache may cause encephalitis, but there is no definite answer as to how long it takes, and it often appears at the same time as the fever or several days later. Usually, fever headaches are the result of upper respiratory tract infections caused by bacterial or viral invasion. Due to the increase in body temperature and vasodilation of the head during fever, the patient will develop a headache, which will be relieved or disappear when the body temperature returns to normal. Only a few patients will cause encephalitis. If a patient’s headache persists without relief or gradually worsens, accompanied by mental discomfort and jet vomiting, it suggests that it may cause encephalitis or meningitis. Patients are recommended to visit regular hospitals in time to do relevant examinations, such as blood routine, cranial CT, EEG, lumbar puncture for cerebrospinal fluid, etc., to clarify the disease diagnosis and actively carry out systematic treatment. Therefore, when fever and headache symptoms occur, if the patient’s body temperature exceeds 38.5℃, in addition to symptomatic treatment, symptomatic treatment with antipyretic and analgesic drugs, such as ibuprofen, acetaminophen, etc., or physical cooling is required at the same time, and relevant examinations are performed to avoid serious consequences.