Patients admitted for autologous or allogeneic hematopoietic cell transplantation, induction-remission chemotherapy for acute myeloid leukemia, myelodysplasia or acute lymphoid leukemia, or to receive immunosuppressive therapy for aplastic anemia will be screened on admission. Patients may be included more than once, provided that a new treatment is administered and >30 days elapses from one to other admission (episode).