Human cytomegalovirus (CMV) does not cause identifiable disease in the vast majority of infections. The major problems result from congenital cytomegalovirus infection. Only 5 to 10 percent of congenital infections are symptomatic, but 1 to 2 percent of these are fatal. Almost 90 percent of symptomatic infections leave sequelae in the survivors. Between 5 and 17 percent of congenitally infected children who are asymptomatic at birth have late sequelae. The acute manifestations of congenital cytomegalovirus infection include hepatic disease, resulting in jaundice, and multiorgan involvement including ocular and cerebral infections (Weller, 1971).

Cytomegalovirus infection also can be acquired in the newborn period, through inoculation of virus from the birth canal during delivery or by ingestion of infected breast milk (Stagno et al., 1980). The disease spectrum associated with perinatal infection has not been well defined, but appears to be less serious than that of congenital infections, although children may develop delayed complications.

Acute infection in a normal host induces antibodies and a specific cell-mediated immune response, but viral shedding may persist for months or even years, and the virus may become latent. Reactivation of CMV infection with viral shedding may occur in asymptomatic patients.

Symptomatic illness after early childhood, resulting from reactivation of the virus or primary infection, usually occurs in immunocompromised hosts. Cytomegalovirus pneumonia and other manifestations may be especially severe and are often fatal in patients who have undergone bone marrow transplants and other procedures that require suppression of the immune system.