Named for the enlarged, inclusion-bearing cells characteristic of infection by these viruses, cytomegaloviruses present a significant challenge to both microbiologist and immunologist. Although most primary infections in humans are subclinical, cytomegalovirus can be associated with a wide spectrum of disease, particularly when infection occurs in the immuno- compromised individual or as a result of congenital or perinatal infection. Although reinfection with cytomegalovirus has been demonstrated, most recurrent and persistent infections result from the reactivation of latent virus....