Medical importance of CMV infection

Cytomegalovirus disease occurs mainly as a result of infections in fetuses and immunocompromised hosts; in each of these patient groups, CMV is a leading (possibly the leading^ infectious cause of morbidity. Among immunocompromised hosts, the probability of experiencing CMV disease is related to the degree of impairment of T-lymphocyte function. Prior to the use of highly active antiretro-viral agents, CMV was a frequent opportunistic infection in AIDS patients. Cytomegalovirus continues to be a major problem for transplant patients; the possibility of CMV infection in such patients has made screening of organ donors, recipients, and blood products used for them standard care. Use of preventive strategies involving antiviral agents for CMV in the first few months after transplant is commonly practiced, and has dramatically reduced the frequency of CMV disease in organ transplant patients. However, aside from the chance transmission of CMV from a young child to a susceptible transplant patient (an event that has rarely been recognized), the problems posed by CMV for transplant medicine are not germane to the current discussion. In contrast, child care may be the source of virus for many congenital CMV infections.

It has been estimated that congenital CMV infection occurs in 0.5-1.5 percent of live births. The majority of the approximately 40,000 infants born in the US each year with congenital CMV infection have no clinically evident abnormalities at birth (i.e. are asymptomatic). Around 5-10 percent of newborns with congenital CMV infection have physical signs typical of congenital infection, such as petechiae, jaundice, enlarged spleen and liver, small size for gestational age, and chorioretinitis; some have clear evidence of involvement of the central nervous system, such as microcephaly, hearing loss, lethargy, hypotonia, or seizures (Istas et al., 1995). The public health impact of congenital CMV infection is the result of central nervous system sequelae. Among infants who are symptomatic at birth, 50-90 percent will have cognitive impairment, motor abnormalities (cerebral palsy), sensorineural hearing loss, or impaired vision. Among the larger group that are asymptomatic at birth, hearing loss is the most frequently encountered adverse outcome, and it occurs in 7-15 percent of them. Congenital CMV infection is a leading cause of sensorineural hearing loss and mental retardation in young children. An expert panel from the Institute of Medicine of the National Academy of Sciences estimated that from 5000 to 8000 infants born in the US each year will have cognitive, motor, or sensory deficits due to congenital CMV infection (Stratton et al, 2001). The same panel also concluded that, based on health-care costs and quality adjusted life years lost, a vaccine aimed at prevention of congenital CMV should be a top priority in the US.

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