Human Cytomegalovirus

An Enormous Variety of Strains and Their Possible Clinical Significance in the Human Host

Elisabeth Puchhammer-Stöckl; Irene Görzer


Future Virology. 2011;6(2):259-271. 

In This Article

Abstract and Introduction


Human cytomegalovirus (HCMV) does not exist as one defined virus genotype, but as a variety of different strains. Several studies have investigated the significance of specific viral genotypes for the clinical course of HCMV infection. Upon reinfection, patients may acquire additional HCMV strains, and infections with a mixture of HCMV strains appear to be quite common. The analysis of such mixed infections has become increasingly important, not only for investigating the clinical implications of mixed-genotype infections, but also for understanding the pathogenesis of subsequent reinfections with HCMV strains, and this is also of importance for HCMV vaccine development. This article summarizes the clinical implications of infection with individual HCMV genotypes and focuses on infection with mixed populations of HCMV strains.


Human cytomegalovirus (HCMV) is a human betaherpesvirus (family Herpesviridae, subfamily Betaherpesvirinae, genus Cytomegalovirus, type species Human herpesvirus 5), which, after primary infection, remains in a latent state for the entire lifetime of the host.[1] HCMV has a ubiquitous distribution, with between 40 and 90% of all adults worldwide carrying the virus.[1,2] In immunocompetent hosts, HCMV usually causes a mild or asymptomatic infection, but it is highly pathogenic in immunosuppressed patients and causes potentially lethal infections, especially in transplant recipients and AIDS patients.[1,3] In addition, HCMV is an important viral cause of fetal infection and may lead to severe clinical complications in the newborn child, such as encephalitis, chorioretinitis, pneumonia, microcephaly and hearing loss, as well as impaired cognitive development.[1,3]

Recently, with the development of sensitive methods that allow different virus strains to be distinguished, it has become increasingly evident that both laboratory and wild-type HCMV strains exhibit substantial genetic variation. As knowledge about the large variety of virus strains has increased, it has also become clear that, in HCMV infections of patients, we are dealing with an enormous variety of different virus strains and not with one clearly defined genotype. Thus, a number of efforts have been made within the last few years to understand how different HCMV strains might influence the course of infection and the development of HCMV disease in the individual host.


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