Cytomegalovirus (CMV) is a member of the family Herpesviridae, which includes Epstein-Barr virus, herpes simplex virus types 1 and 2, varicella-zoster virus, and human herpesvirus 6. CMV is the most common identified cause of congenital infection. Found in several body fluids including saliva, urine, breast milk, cervical secretions, blood, and semen, CMV can be transmitted in a variety of ways, such as blood transfusion and organ transplantation. The typical morphology of infected tissue includes enlarged cells (often to a diameter of 40 mm) with intranuclear, and on occasion, cytoplasmic inclusions. The intranuclear inclusions may measure 17mm in diameter and are usually set off from the nuclear membrane by a clear halo. Not all CMV-infected cells demonstrate the “classic” cytopathic effects associated with antigen of 68 kD found in the nucleus of infected cells. It also immunoprecipitates antigens of 38, 43, 46, and 49 kD.