Bacterial infection with high fever around 40℃ is not necessarily leukemia, it is recommended to promptly seek medical examination to clarify the cause and take appropriate measures. Bacterial infection with high fever of about 40°C is usually considered to be caused by bacterial infection. Of course, patients with leukemia may also have bone marrow suppression, resulting in a significant decrease in granulocytes in the blood and lower resistance, which can cause bacterial infections and result in high fever. In severe cases, sepsis and septicemia may develop. Since high fever is caused by bacterial infection, treatment should first determine the bacteria causing the infection, first empirically select appropriate antibacterial drugs to control the infection, and then adjust the antibacterial drugs appropriately when the bacterial culture results are available. A variety of diseases such as lobar pneumonia and suppurative appendicitis may be caused by bacterial infections with symptoms of high fever. Thus, a high fever of about 40°C in bacterial infection is not necessarily leukemia. In addition, it is recommended that the patient can be given a warm water bath all over the body to help cool down the fever, or ice and cold towels can be used for local cooling, but be careful to avoid direct ice contact with the skin. At the same time, patients should actively hydrate, pay attention to rest and avoid exertion.