Cytomegalovirus overview
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Cytomegalovirus (CMV) (from the Greek cyto-, "cell", and -mega-, "large") is a viral genus of the Herpesviruses group.[1] CMV belongs to the Betaherpesvirinae subfamily of Herpesviridae, which also includes Roseolovirus, also known as Human Herpes Virus 6 (HHV-6). The Alphaherpesvirinae contains herpes simplex virus types 1 and 2, and varicella-zoster virus (which causes chickenpox and shingles). The Epstein-Barr virus [1] belongs to the Gammaherpesvirinae subfamily. The herpesviruses share a characteristic ability to remain latent within the body over long periods.
CMV infections are frequently associated with salivary glands, though they may be found throughout the body. CMV infection can also be life threatening for patients who are immunocompromised (e.g. patients with HIV, organ transplant recipients, or neonates).[1] CMV viruses are found in many mammal species, but CMV species isolated from animals differ from human CMV in terms of genomic structure, and have not been reported to cause human disease.
In humans, CMV is found throughout all geographic locations and socioeconomic groups, and infects between 50% and 80% of adults in the United States as indicated by the presence of antibodies in much of the general population.[1] CMV is also the virus most frequently transmitted to a developing child before birth. CMV infection is more widespread in developing countries and in areas of lower socioeconomic conditions and causes the most birth defects in industrialized countries of all the herpes viruses.
Epidemiology and Demographics
CMV is the most common cause of congenital infection in humans and intrauterine primary infections are second only to Down's syndrome as a known cause of mental retardation.[2] The incidence of primary CMV infection in pregnant women in the United States varies from 1% to 3%. Healthy pregnant women are not at special risk for disease from CMV infection. CMV remains the most important cause of congenital viral infection in the United States.
Diagnosis
Laboratory Findings
Most infections with CMV are not diagnosed because the virus usually produces few, if any, symptoms and tends to reactivate intermittently without symptoms. However, persons who have been infected with CMV develop antibodies to the virus, and these antibodies persist in the body for the lifetime of that individual. A number of laboratory tests that detect these antibodies to CMV have been developed to determine if infection has occurred and are widely available from commercial laboratories. In addition, the virus can be cultured from specimens obtained from urine, throat swabs, bronchial lavages and tissue samples to detect active infection. Both qualitative and quantitative polymerase chain reaction (PCR) testing for CMV are available as well, allowing physicians to monitor the viral load of CMV-infected patients. The enzyme-linked immunosorbent assay (or ELISA) is the most commonly available serologic test for measuring antibody to CMV.
Treatment
Medical Therapy
No treatment is generally necessary for CMV infection in the healthy individual since the majority of infections resolve on their own. Antiviral drug therapy is now being evaluated in infants. Ganciclovir treatment is used for patients with depressed immunity who have either sight-related or life-threatening illnesses. Valganciclovir (marketed as Valcyte) is an antiviral drug that is also effective and is given orally. The therapeutic effectiveness is frequently compromised by the emergence of drug-resistant virus isolates. A variety of amino acid changes in the UL97 protein kinase and the viral DNA polymerase have been reported to cause drug resistance. Foscarnet or cidofovir can be given in patients with CMV resistant to ganciclovir, though foscarnet is not as well tolerated as ganciclovir.
Future or Investigational Therapies
Vaccines to help prevent CMV infection are still in the research and development stage.