Cytomegalovirus is a member of the herpes virus group, which includes herpes simplex virus types 1 and 2, varicella zoster virus (which causes chicken pox), and Epstein Barr virus (which causes infectious mononucleosis). These viruses share a characteristic ability to remain dormant within the body over a long period. CMV viral genes are co-ordinately expressed in groups at various times after infection. Early viral proteins are expressed in the nucleus of infected cells within 3 to 24 hours