Pyrexia is a fatal disease whose clinical manifestations are mainly hyperthermia and delirium. The body temperature mostly exceeds 40℃. The treatment mainly includes the following aspects: 1. cooling treatment cooling treatment contains three aspects: 1. for external cooling, that is, the patient is transferred to a well-ventilated low-temperature environment, remove clothing, cold water bath to help dissipate heat, or use fans or air conditioning to help reduce body temperature. 2. is internal cooling, that is, ice saline for gastric or rectal irrigation. 3. is drug cooling. Complications: 1. coma, 2. arrhythmia, 3. hypotension, 4. liver and kidney failure, 5. diffuse intravascular coagulation. Patients in coma should be endotracheally intubated to keep the airway open, and those with cerebral edema should be treated with mannitol to lower cranial pressure. Those with seizures can be treated with intravenous diazepam infusion. Symptomatic treatment should be given for cardiac arrhythmias, hypotension and hepatorenal syndrome. Finally, close monitoring of body temperature changes is needed.