Adults who have fever for a while and then don’t have fever are classified as febrile, and the common causes of fever are infection-induced fever and non-infection-induced fever. The common causes of fever are infection-induced fever and non-infection-induced fever. The classification of fever as intermittent is based on the type of fever. Intermittent fever means that the body temperature rises and then gradually returns to normal, with normal intervals, and the intermittent period alternates with the febrile period. Intermittent fever occurs commonly in infections of the urinary system such as pyelonephritis, infectious diseases such as epidemic hemorrhagic fever, spotted fever, typhoid fever, malaria and other diseases. Intermittent fever has a sudden onset and alternates between fever and no fever. Clinically, the most typical disease of intermittent fever is malaria, when infected with malaria, the alternation of fever and no fever is obvious. Intermittent fever can also be seen in patients with advanced tumors, due to the destruction of the autoimmune system, or the stimulation of tumor factors and the emergence of intermittent fever. Adults may have other causes of fever, and it is recommended to go to the hospital in time to find out the cause of the disease and give targeted treatment.