Cytomegalovirus

Cytomegalovirus (from the Greek cyto-, "cell", and -megalo-, "large") is a viral genus of the viral group known as Herpesviridae or herpesviruses. It is typically abbreviated as CMV: The species that infects humans is commonly known as human CMV (HCMV) or human herpesvirus-5 (HHV-5), and is the most studied of all cytomegaloviruses.^[1] Within Herpesviridae, CMV belongs to the Betaherpesvirinae subfamily, which also includes the genera Muromegalovirus and Roseolovirus (HHV-6 and HHV-7).^[2] It is related to other herpesviruses within the subfamilies of Alphaherpesvirinae that includes herpes simplex viruses (HSV)-1 and -2 and varicella-zoster virus (VZV), and the Gammaherpesvirinae subfamily that includes Epstein–Barr virus.^[1] All herpesviruses share a characteristic ability to remain latent within the body over long periods. Although they may be found throughout the body, CMV infections are frequently associated with the salivary glands in humans and other mammals.^[2] Other CMV viruses are found in several mammal species, but species isolated from animals differ from HCMV in terms of genomic structure, and have not been reported to cause human disease.

Species

Several species of cytomegalovirus have been identified and classified for different mammals.^[2] The most studied is human CMV (HCMV), which is also known as human herpesvirus-5 (HHV-5). Other primate CMV species include chimpanzee CMV (CCMV) that infects chimpanzees and orangutans, and simian CMV (SCCMV) and rhesus CMV (RhCMV) that infect macaques; CCMV is known as both panine herpesvirus-2 (PaHV-2) and pongine herpesvirus-4 (PoHV-4), SCCMV is also called cercopithecine herpesvirus-5 (CeHV-5) and RhCMV is also called cercopithecine herpesvirus-8 (CeHV-8). A further two viruses found in the night monkey are tentatively placed in the cytomegalovirus genus, and are called Herpesvirus aotus 1 and Herpesvirus aotus 3. Rodents also have viruses previously called cytomegaloviruses that are now reclassified under the genus muromegalovirus; this genus contains mouse CMV (MCMV) is also known as murid herpesvirus 1 (MuHV-1) and the closely related murid herpesvirus 2 (MuHV-2) that is found in rats. In addition, there many other viral species with the name cytomegalovirus identified in distinct mammals that are as yet not completely classified; these were predominantly isolated from primates and rodents.

HCMV

Human cytomegalovirus is a species of virus that belongs to the viral family known as Herpesviridae or herpesviruses. It is typically abbreviated as HCMV and is alternatively known as human herpesvirus-5 (HHV-5).^[1] Within Herpesviridae, HCMV belongs to the Betaherpesvirinae subfamily, which also includes cytomegaloviruses from other mammals.^[2]

Although they may be found throughout the body, HCMV infections are frequently associated with the salivary glands.^[2] HCMV infection is typically unnoticed in healthy people, but can be life-threatening for the immunocompromised, such as HIV-infected persons, organ transplant recipients, or new born infants.^[1] After infection, HCMV has an ability to remain latent within the body over long periods. A prevention by hygienic measures is included in information given to pregnant women.^[3]

HCMV is found throughout all geographic locations and socioeconomic groups, and infects between 50% and 80% of adults in the United States (40% worldwide^[4]) as indicated by the presence of antibodies in much of the general population.^[1] Seroprevalence is age-dependent: 58.9% of individuals aged 6 and older are infected with CMV while 90.8% of individuals aged 80 and older are positive for HCMV.^[5] HCMV is also the virus most frequently transmitted to a developing fetus. HCMV infection is more widespread in developing countries and in communities with lower socioeconomic status and represents the most significant viral cause of birth defects in industrialized countries. CMV "seems to have a large impact on immune parameters in later life and may contribute to increased morbidity and eventual mortality."^[6]

References