If a low fever does not go away it is not necessarily a precursor to leukemia, but there is the possibility of having a hematological disorder. First, from the perspective of hematological disorders, a low fever that does not go away may be a case of leukemia, and there is also the possibility of pernicious anemia or aplastic anemia. Secondly, from the point of view of other non-hematologic system, a prolonged low fever is caused by excessive low immunity of the body, which can lead to other diseases, such as tuberculosis, rheumatism, connective tissue disease, and even malignant tumors and AIDS, all of which can cause a low fever. Third, infectious factors such as bacteria, viruses, fungi, atypical pathogens such as mycoplasma and chlamydia infect the body, if the long-term in the body continued to have bacterial infection, there will also be a low fever does not go away.