Human cytomegalovirus (HCMV)
infections are the major viral complications associated with the post-transplant period in haematopoietic stem cell and solid organ transplant recipients. HCMV
infection may be systemic (high viral load in blood associated with
fever, leucopenia and
thrombocytopenia) or local (clinical symptoms of
viral infection within a single organ [e.g. lungs] or apparatus [gastrointestinal tract]). Both
infection types can be associated with each other. Systemic HCMV
infections are diagnosed by performing antigenaemia or DNAemia assay (polymerase chain reaction [PCR]) on blood samples: both assays are quantitative. Local
infections are diagnosed by virus isolation from tissue biopsies or secretions, or by PCR. To prevent HCMV disease, a prophylactic approach is usual in the USA, while a pre-emptive (presymptomatic) approach, which is more common in Europe, involves administering
antivirals when a predetermined viral load is reached in blood. Simultaneous virological and immunological follow-up is the best approach to efficient monitoring of HCMV
infections in transplant recipients. Lack of immune reconstitution entails repeated episodes of
recurrent infection with multiple courses of
antiviral treatment, whereas reconstitution of both arms of the HCMV-specific T-cell mediated immune response controls HCMV
infection. The exception is for cases of graft rejection or
graft versus host disease treated with
steroids or
antilymphocyte globulin, which require virological monitoring and (in some cases)
antiviral treatment until resolution of the adverse event.