Cytomegaloviruses

Abstract

The cytomegaloviruses are a common, ancient group of viruses that are widely distributed in the animal kingdom. They have a complex biology with a highly restricted host range. These viruses spread easily in the human population, causing mostly asymptomatic infection. This large reservoir of latent infection however, is a significant threat to high‐risk patients including immunocompromised hosts and the fetus in nonimmune pregnant mothers. Although a limited number of antiviral agents for treatment and prophylaxis in selected patient groups, as well as other adjunctive therapies have become available over the past few decades, newer, less toxic medications and a safe and effective vaccine remain in the research realm. Other areas still to be investigated include identification of the site of viral latency, characterisation of the targets of acute infection, determination of the exact role of virus and host immune response in disease and latency. Key Concepts: The cytomegaloviruses (CMVs) belong to the family of deoxyribonucleic acid (DNA) viruses known as Herpesviridae . CMVs have complex biology and are widely distributed in nature, yet each animal species has its own CMV. The prevalence of human CMV infection varies with age, geographic location, cultural and socioeconomic status, race or ethnicity and child‐rearing practices. In most cases, human CMV infection in normal hosts is asymptomatic, but it can cause a mononucleosis syndrome similar to that from Epstein–Barr Virus ( EBv ) infection. The greatest risk from CMV is in immunocompromised patients and infants born to nonimmune mothers who develop primary infection during their pregnancy. CMV has been one of the most important opportunistic infections in patients with AIDS. Antiviral agents used to treat severe CMV disease include ganciclovir, valganciclovir, foscarnet, cidofovir and fomivirsen. Passive immunoprophylaxis with CMV hyperimmunoglobulin (CMVIG) in post‐transplant patients, premature newborns at risk for postnatal infection and pregnant women is controversial. Blood/organ donor screening, ‘leucocyte‐reduction’ in donated blood, handwashing and other hygienic measures can reduce the spread of CMV. Newer therapeutic agents and a vaccine are under development.