Fever in leukemia has a persistent pattern. Persistent fever is the most common symptom of acute leukemia, with more than 50% of patients starting with fever. Most fever is caused by secondary infection, but leukemia itself can also cause fever, i.e. oncogenic fever. 1. Secondary infection: it is the most common cause of death in patients with acute leukemia. It mainly manifests as persistent low or high fever, even ultra-high fever, which may be accompanied by chills, chills and sweating. Local manifestations include inflammation, ulceration, abscess, and in severe cases, sepsis or septicemia. The most common causative organisms are gram-negative bacilli, such as Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, and Clostridium perfringens. Some patients also have infections of viruses (e.g. herpes zoster) and protozoa (e.g. Pneumocystis carinii). 2. Oncogenic fever: it is related to the high metabolism of leukemia cells and the production of endogenous pyrogen. It is mainly characterized by persistent low to moderate fever in the body, which may be accompanied by hyperthermia. Traditional antibiotic therapy such as levofloxacin is ineffective. It is recommended to actively seek medical attention to identify the cause of the disease and provide targeted treatment under the guidance of a physician.