Cytomegalovirus (CMV), also known as human herpesvirus 5, is a member of the herpes family of DNA viruses. CMV infection is common, and by adulthood, 80% of the world population will have developed antibodies indicating past primary infection. CMV infections are acquired through exposure to body fluids and secretions (eg, urine, saliva, blood, vaginal secretions, semen, and breast milk).

Primary CMV infection is generally asymptomatic in the vast majority of people. Occasionally, an infectious mononucleosis-like illness may occur in adults and older children. The symptoms are identical to traditional mononucleosis caused by the Epstein-Barr virus (EBV) and include sore throat without exudate, fever, malaise, and myalgias. Rare reported sequelae of primary CMV include hemolytic anemia, interstitial pneumonia, meningoencephalitis, and Guillain-Barré syndrome.

Like other herpesviruses, CMV establishes a latent infection that may reactivate during periods of relative immunosuppression. In immunocompromised individuals, reactivation and proliferation of the virus can range from asymptomatic viremia to febrile illness to focused end-organ disease with a variety of clinical presentations.

Risk for CMV reactivation depends on the nature and state of a patient's immunosuppression and, with respect to solid-organ and bone-marrow transplant recipients, depends on both the donor's and recipient's immune status.

Asymptomatic CMV viremia in solid-organ transplant recipients still warrants evaluation and, in some cases, treatment. The virus is immunosuppressive in its own right, increasing the patient's risk for other opportunistic infections, and has "secondary effect" and increases the risk of allograft rejection.

End-organ disease with CMV is fairly protean with involvement of the gastrointestinal tract being the most common presentation. Evaluation and management of CMV colitis is complicated by the fact that patients with active CMV colitis may have negative CMV blood viral loads. Ultimately, the diagnosis must be made via tissue biopsy and histological evaluation.

CMV pneumonitis is most often identified in lung-transplant recipients and carries a high morbidity and mortality. In bone-marrow transplant recipients, the lung injury due to CMV is due to the immune response and often coincides with engraftment.

CMV disease in human immunodeficiency virus (HIV) patients most commonly presents with CMV retinitis in patients with AIDS and CD4 counts lower than 50/mm³. The advent of effective antiretroviral treatment (ART) options has resulted in a significant reduction in the incidence of CMV retinitis by over 80%.

Related topic: cytomegalovirus infection of newborn