The first step is to look at the patient’s past medical history and to identify the cause of the sudden fever in conjunction with some other clinical manifestations other than the fever, before treating it symptomatically. Sudden onset of fever is more common in influenza. Patients often develop a high fever, which may be accompanied by congestion of the throat wall and even enlarged tonsils. In addition to this sudden fever is also related to some acute infections of the respiratory system, such as pneumonia, which is common in life, where patients may have chills, high fever, chest pain, cough, coughing and even difficulty in breathing. Some acute phase infections of the urinary system, such as urinary tract infections and acute nephritis, may also present with sudden fever. Some patients with cerebrovascular diseases in a comatose state (such as cerebral hemorrhage) may have a stress reaction and may also develop sudden fever. Blood disorders such as acute stage leukemia can have sudden fever. If the patient has a history of unclean sexual life, it is necessary to exclude infectious diseases such as AIDS, syphilis, gonorrhea, hepatitis, etc. When a sudden fever occurs, you should not blindly use antipyretic drugs to reduce the fever, because fever is a symptom of a disease in the body system, and must be combined with clinical manifestations and laboratory tests to identify the cause of the disease in order to cure it.