Due to a variety of different reasons to cause the body to produce heat than heat dissipation, so that the body temperature exceeds the normal range is called fever (fever), clinically, according to the degree of heat will be divided into low fever, moderate fever, high fever and ultra-high fever. Hyperthermia refers to body temperature over 39.1℃. Diagnosis: (a) the main points of history: detailed history, pay attention to: 1, the trigger: fever 2 ~ 3 weeks before the history of skin trauma and carbuncle; 1 ~ 3 weeks in the past history of infectious disease infected area stay; 1 months of schistosomiasis infected water contact history. Skin trauma and carbuncles are clues to the diagnosis of sepsis. A history of staying in infectious disease infected area is considered acute infectious disease; fever after abdominal surgery should be considered abdominal and pelvic infections such as subdiaphragmatic abscess, intestinal interstitial abscess, and cavernous organ fistula. 2, the onset of the season: the onset of winter and spring, most common in measles, epidemic cerebrospinal meningitis; summer and fall season onset, most common in encephalitis B, malaria, typhoid fever, dysentery, heat stroke. (1)Auditory fever: seen in lobar pneumonia, typhoid fever, typhus fever, etc. (2) Intermittent fever: seen in malaria, acute pyelonephritis, limited septic infection, etc. (3)Flaccid fever: seen in sepsis, rheumatic fever, severe tuberculosis, exudative meningitis, purulent inflammation, etc. (4)Regression fever: seen in regression fever, Hodgkin’s disease, plague fever, etc. (5) undulating fever: seen in brucellosis, malignant lymphoma, peritonitis, etc. (6) Irregular fever: seen in tuberculosis, infective endocarditis, rheumatic fever, etc. (7) Consumptive fever: seen in septicemia, sepsis, etc. (8) Bimodal fever: seen in gram-negative bacillus sepsis. 4, the way of temperature rise and fall: sudden rise type fever is seen in malaria, acute pyelonephritis, lobar pneumonia, sepsis, infusion reaction, etc.; slow rise type fever is seen in the early stage of typhoid fever, tuberculosis, brucellosis, etc.; sudden fall type is seen in malaria, acute pyelonephritis, lobar pneumonia, infusion reaction, and those who are taking antipyretic; gradual descent is seen in the period of remission of typhoid fever, rheumatic fever, and infectious diseases when antibiotic treatment is effective. 5, accompanying symptoms: (1) fever with chills, mostly seen in sepsis, lobar pneumonia, acute cholecystitis, acute pyelonephritis, epidemic cerebrospinal meningitis, malaria, drug fever, acute hemolysis and infusion reaction, epidemic typhus, psittacosis, smallpox, epidemic hemorrhagic fever, infectious mononucleosis. (2) Accompanied by sore throat, mostly seen in upper respiratory tract infection, purulent tonsillitis; accompanied by cough and sputum, seen in acute respiratory tract infection and lung infection. (3) With chest pain, see pneumonia, pleurisy, myocardial infarction, lung abscess and so on. (4) Accompanied by abdominal pain, nausea, vomiting, seen in acute bacillary dysentery, acute cholecystitis, acute pyelonephritis, acute mesenteric lymphadenitis, acute hemorrhagic necrotizing enterocolitis, acute pancreatitis, acute gastroenteritis and so on. (5) Accompanied by headache, seen in encephalitis, meningitis, brain abscess, etc. (6) Those with muscle pain are seen in myositis, dermatomyositis, trichinosis, legionnaires’ disease, leptospirosis, drug fever and so on. (7) Generalized arthralgia is seen in connective tissue disease, gout, psoriatic arthritis, etc. (8) Accompanied by neurological disorders, seen in encephalitis, meningitis, infectious toxic encephalopathy, cerebral hemorrhage, heat stroke, temporal arteritis, lupus erythematosus encephalopathy, and so on. (9) Fever with obvious toxic symptoms is seen in severe infections, especially sepsis. (10) Whether accompanied by rash and the time of rash: rash on the 1st day of fever is seen in chickenpox; rash on the 2nd day is seen in scarlet fever; rash on the 3rd day is seen in smallpox; rash on the 4th day is seen in measles; rash on the 5th day is seen in typhus; rash on the 6th day is seen in typhoid fever. (ii) Physical examination: A comprehensive physical examination should be done, but attention should be paid to: 1. General condition and general skin and mucous membrane examination, and attention to general nutritional status. Malignancy suggests severe tuberculosis, malignant tumor. Note the presence of rash and the type of rash: maculopapular rash is seen in dengue, typhus; butterfly-shaped erythema on the face, erythema on the fingertips and peri-nail suggests systemic lupus erythematosus (SLE); annular erythema is seen in rheumatic fever; papules and maculopapular rash is seen in scarlet fever, drug fever; roseola is seen in typhoid fever and paratyphoid fever. Few bruises on lid conjunctiva and skin; osler nodules with pressure on finger tips, toes, and large and small piriformis muscles are seen in infective endocarditis. Striated or scratch-like hemorrhagic spots on the soft palate and axilla are seen in epidemic hemorrhagic fever. Scattered cutaneous bruises, sloughs, and purpura are seen in aplastic anemia, acute leukemia, and malignant connective tissue disease. Large bruises suggest diffuse intravascular coagulation; sepsis and septicemia should be considered in skin boils. 2, pay attention to the generalized lymph nodes are not enlarged. Localized lymph nodes are enlarged, soft and tender with tenderness, and inflammation in the corresponding drainage area should be considered. Localized lymph nodes are enlarged, hard and without pressure and pain, which may be metastasis of cancer or lymphoma. Systemic lymph node enlargement can be seen in lymphoma, acute and chronic leukemia, infectious mononucleosis, systemic lupus erythematosus and so on. 3, head and neck examination: conjunctival congestion is often seen in measles, hemorrhagic fever, typhus; enlarged tonsils with yellowish-white exudate are considered as purulent tonsillitis; purulent secretion from the external ear canal is purulent otitis media; redness, swelling, and pressure pain in the mastoid process is mastoiditis; neck straightness is seen in meningitis and meningoencephalitis; enlarged thyroid gland with protruding eyes and high temperature is seen in hyperthyroidism crisis. 4, heart condition: heart enlargement, new systolic murmur suggests rheumatic fever. The original heart valve disease, the murmur of the nature of the change, to consider infective endocarditis. 5, lung examination: one side of the lung confined turbidity, tremor enhancement, wet rhonchi, suggesting lobar pneumonia; lower chest or back fixed or recurrent wet rhonchi, seen in bronchial dilatation associated with secondary infections, one side of the lungs lower percussion is turbid, respiratory sounds, tremor reduction, suggesting pleural effusion. 6.Abdominal examination: gallbladder point pressure and pain, Murphy’s sign is positive, accompanied by skin and sclera yellow staining, suggesting cholecystitis, cholelithiasis fever. Obvious pressure and pain in the middle and upper abdomen, gray-purple spots on the skin of the rib abdomen (Grey-Turner’s sign) or bruising of the skin around the umbilicus (Gullen’s sign) are seen in hemorrhagic necrotizing pancreatitis. Pressure pain in the right lower abdomen or the whole abdomen, sometimes accompanied by abdominal masses, fistula in the abdominal wall or perineum, poor general nutrition, consider Crohn’s disease (Crohn’s disease). Hepatomegaly, hardness, nodules or giant lumps on the surface, suggesting hepatocellular carcinoma fever. Simultaneous enlargement of liver and spleen can be seen in leukemia, lymphoma, malignant histiocytosis, systemic lupus erythematosus. Pressure pain at quarter rib point and percussion pain in kidney area suggest upper urinary tract infection. 7, limbs and nervous system examination: pestle finger with fever, seen in lung cancer, lung abscess, bronchiectasis, infective endocarditis. Redness, swelling and tenderness of joints can be seen in rheumatic fever, lupus erythematosus or rheumatoid arthritis. Positive Kirschner’s sign or Bucher’s sign is seen in central nervous system infection. (C), laboratory tests Because of the many causes of fever, should be based on the cause of the targeted examination, but should be the following routine examination: 1, blood routine, urine routine, fecal routine. Neutrophil increase with fever, commonly seen in bacterial infection, hemorrhage, tissue injury; neutropenia, seen in typhoid fever, paratyphoid fever, acute viral infection, malaria, black fever, acute aplastic anemia, pernicious histiocytosis, systemic lupus erythematosus, acute disseminated tuberculosis, acute non-leukemic leukemia, acute agranulocytosis and so on. Eosinophilia is commonly seen in drug fever and serum sickness; eosinopenia is seen in typhoid fever. High fever with anemia is seen in acute hemolysis, acute aplastic anemia, acute non-leukemic leukemia. 2, chills and high fever should be made blood culture, blood smear examination. Blood smear examination: it is helpful to diagnose malaria, regression fever, leukemia, systemic lupus erythematosus, leptospirosis and so on. 3.High fever for more than 1 week, should be made fertilization reaction and exophthalmos reaction, brucella agglutination test. 4, suspected of respiratory disease, should do chest fluoroscopy or chest X-ray, sputum culture, sputum smear examination. 5.Suspect liver disease, should do liver function and abdominal ultrasound. 6.With bleeding tendency, clotting time, platelet, prothrombin time measurement should be made. 7.Suspect urinary system infection, should do urine culture. 8, with joint pain, should do anti-streptococcal hemolysin “O” test and C-reactive protein, anti-nuclear antibody, blood sedimentation, serum protein electrophoresis, immunoglobulin and other tests. 9.It is necessary to do lymph node biopsy and bone marrow biopsy if the cause of high fever is unknown and antibiotics are ineffective. 10.Serological examination: Fertilizer reaction is positive, seen in typhoid fever, paratyphoid fever; Exophthalmos reaction is positive, consider typhus fever; Brucella agglutination test is positive, consider brucellosis; eosinophilic agglutination test is positive, consider infectious mononucleosis; condensate collection test is positive, consider mycoplasma pneumonia and so on.