cytomegalovirus (sī´təmĕg´əlōvī´rəs), member of the herpesvirus family that can cause serious complications in persons with weakened immune systems. A common virus, it is estimated that up to 80% of Americans carry cytomegalovirus by the time they reach adulthood. Most experience no symptoms or mild symptoms such as enlarged lymph nodes, low fever, and fatigue that may or may not be noticed. Cytomegalovirus is present in body fluids (saliva, semen, cervical secretions, and urine) and can be spread from person to person by sexual contact, kissing, or the sharing of food. It can also be transmitted from mother to fetus. The virus usually remains dormant in the body, but it can reactivate and cause serious symptoms in immunologically suppressed patients, such as those with AIDS, or in infants whose immune systems are not yet fully developed. An estimated 25% of AIDS patients experience CMV infection, often in the form of a viral retinitis that can lead to blindness. Infants can become infected before birth when the mother becomes infected or experiences a recurrence during pregnancy. In a newborn, CMV can be life-threatening, and it can lead to later complications such as cerebral palsy, blindness, hearing problems, mental retardation, and learning disabilities. The antiviral drugs foscarnet and ganciclovir are used to keep active infections under control.