HLA-DRB1 and graft versus host disease: Risk factors associated with CMV reactivation include seropositivity of the recipient, reduced intensity conditioning, graft-versus-host disease (GVHD), human leukocyte antigens (HLA-B14, HLA-DRB1*01 and HLA-DRB1*13), donor activating killer immunoglobulin-like receptors (KIR) and use of high dose corticosteroids [2,3,5].