Recent developments in new and old viral infections.

Until recently, concerns regarding viral infections and hematologic malignancies were primarily focused on the transplantation of an allogeneic graft. In the last years, the use of immunomodulatory agents such as monoclonal antibodies (e.g. anti CD20, anti CD52) directed against lymphocyte antigens in the treatment of hematopoietic malignancies (e.g. lymphoma, chronic lymphocytic leukemia) has added a great potential to impact on the incidence, severity and timing of viral infections. Patients may acquire viral infections through several mechanisms including transfusion, community exposure or via the donor origin in the case of stem cell transplant. Endogenous reactivation of latent viruses is also commonly observed. Viral replication may lead directly to viral diseases or induce indirect effects such as increased incidence of opportunistic infections and decreased patient survival. Traditionally, herpesviruses have been and are still today the most important viruses in patients with hematologic malignancies. Nowadays, several emerging viral infections have been highlighted as being of concern in this patients' population.