Patients with blood malignancies such as non-Hodgkin lymphoma, chronic lymphocytic leukemia, acute myeloid leukemia, acute lymphoblastic leukemia and multiple myeloma are most at risk.
Also at risk:
those in active treatment for any type of cancer
and those who have undergone bone marrow transplants.
(Active treatment is usually defined as surgery, radiation, chemotherapy and other treatments such as immunotherapies.)