Human cytomegalovirus (CMV) is a ubiquitous pathogen found in 40–100% of adults, and in about 1% of live births in the United States (1 ). It is the most common fetal and perinatal infectious organism; approx 10% of infected neonates are born with symptomatic congenital CMV disease, which is the most common cause of mental retardation and childhood deafness. CMV is a significant pathogen in immunocompromised individuals, including organ transplant recipients (2 –4 ), and in acquired immune deficiency syndrome (AIDS) patients (5 ,6 ). Infection is characterized by latency, chronic infection, and reactivation, a progression similar to that observed in other members of the herpesvirus family. Because CMV infection is usually controlled by the host cellular immune system, primary infections can occur without obvious symptoms, and progress to latency may go unnoticed. Latent infection may persist throughout life, but primary or reactivated infection, coupled with impaired host immune response, can rapidly produce symptomatic CMV disease.
