A fever that does not go away for a week may be caused by an uncontrolled infectious disease, a reinfection, or a non-infectious disease. 1. The most common cause of fever is infectious diseases, if the infection is not controlled, the fever may last for a week or even longer, at this time it is best to carry out blood cultures or other body fluid cultures to clarify the pathogens and then carry out targeted treatment. 2. Infectious disease patients in the anti-infectious treatment, may induce secondary infection, especially fungi, this time can also appear fever does not go away. 3. Non-infectious fever, such as cancer fever, absorption fever, autoimmune diseases, etc., if the anti-infective treatment is often ineffective, at this time will continue to fever, need to improve the relevant antibodies or imaging tests, clear diagnosis and then for the cause of the treatment.