The modern medical understanding of fever is that it corresponds to an increase in body temperature, which is divided into physiological and pathological. Physiological body temperature elevation is commonly seen in strenuous exercise, premenstrual period, psychological stress, etc. Pathological fever can be seen in a variety of disease processes, and most of its symptomatic manifestations are similar, so clinically flaccid fever needs to be diagnostically differentiated from the following diseases. The following diseases need to be diagnosed and differentiated from flaccid fever: 1. Retained fever The body temperature is maintained at a high level of 39℃-40℃ or more for several days or weeks, and the temperature does not fluctuate more than 1℃ within 24 hours. Commonly seen in pneumococcal pneumonia, typhus and typhoid fever hyperthermia. 2, intermittent fever clinical fever or chills, body temperature rises suddenly, up to 39 ℃ or more, for a few hours and then drop to normal or below normal, intermittent hours to days and so repeatedly, called periodic fever. It is seen in malaria, such as Plasmodium inter vivax or Plasmodium trisomy 21. Irregular fever The range of temperature fluctuation is extremely irregular, and the duration is not certain, and the temperature curve is irregular. The body temperature is often around 38℃ or fluctuates between 37℃ and 40℃. It can be seen clinically in a variety of diseases, such as upper respiratory tract infection, mycoplasma pneumonia, tuberculosis, pleurisy, infective endocarditis, rheumatic fever, leukemia, etc. It can also be seen as a result of interference with medication or physical cooling. 4, wave fever The body temperature gradually rises, and then gradually drops to low fever or normal temperature after a few days, and then gradually rises again after a few days, and so on repeatedly, the body temperature curve is wave-shaped, which is seen in brucellosis.