Cytomegalovirus (CMV) is a member of the herpes virus group, which includes herpes simplex virus types 1 and 2, varicella-zoster virus (which causes chickenpox), and Epstein-Barr virus (which causes infectious mononucleosis). Infection with CMV is a major cause of disease and death in immunocompromised patients, including organ transplant recipients, patients undergoing hemodialysis, patients with cancer, patients receiving immunosuppressive drugs, and HIV-infected patients. While drugs are available for treatment of these conditions, the primary drug choices carry significant side effects and warnings. Currently, there are no anti-CMV drugs indicated for treatment of primary CMV infection during pregnancy resulting in infections that can have catastrophic consequences to the newborn. Maternal-fetal transfer of CMV infection results in a fetal death rate of 12% and most survivors have permanent debilitating disorders, including mental retardation, vision loss, and sensorineural deafness.