[Key definitions and concepts in cytomegalovirus: infection versus disease. Replication, viral load, universal prophylaxis. Preemptive therapy].

Although advances have been made in the prevention, diagnosis and treatment of cytomegalovirus (CMV), this infection continues to be a major complication in transplant recipients, causing considerable morbidity and occasionally mortality. There is wide variability in definitions of CMV infection, which can lead to conceptual errors. The present article attempts to standardize the definitions used, which have recently been revised and recommended by the American Society of Transplantation for the purpose of developing consistent reporting of CMV in clinical trials. The concepts of infection and viral replication, persistence and recurrence of infection, viremia and disease are discussed, together with the diagnostic criteria for febrile syndrome and visceral involvement. Methods for preventing CMV infection, universal prophylaxis and preemptive therapy are also mentioned.