Are malignant blood diseases infectious diseases? The answer is: not an infectious disease. Although the exact cause of human malignant hematologic diseases is still unclear and there are many theories on the pathogenesis of malignant hematologic diseases, there is no case of malignant hematologic disease being transmitted through close contact with a patient with malignant hematologic disease. Although some studies have found that certain viral infections, such as human T-lymphotropic virus, type I (HJLV-1), can induce certain T-cell malignant hematological diseases, which are mainly caused by the genetic mutation of patients due to the retroviral DNA contained in these viruses, although the onset of the disease is caused by the infection of these viruses, there are also intrinsic factors in these patients. It has also been reported that in some families, several members of the family suffer from the same type of malignant blood disease, but this is not due to contagion, but mainly due to certain genetic defects shared by members of the family. If malignant blood diseases are contagious, then health care workers who are in close contact with patients with malignant blood diseases should be the first victims, but in practice, we have not seen any malignant blood diseases among health care workers.