CMV has been found in the saliva, urine, semen, breast milk, feces, blood, and vaginal and cervical secretions of infected people. The virus is usually transmitted via contact with these infected secretions, which can harbor the virus for months or even years. It may be transmitted by sexual contact and can travel across the placenta, causing a congenital infection. Immunosuppressed patients, especially those who have received transplanted organs, run a 90% chance of contracting CMV infection. Recipients of blood transfusions from donors with positive CMV antibodies are at some risk.

Between 50% and 80% of adults in the United States are infected with CMV by age 40; infection usually occurs during childhood or early adulthood. Approximately 1 in 150 children is born with congenital CMV infection. In most of these infants, the disease is so mild that it’s overlooked.

CMV infection during pregnancy can be hazardous to the fetus, possibly leading to stillbirth, brain damage, and other birth defects or to severe neonatal illness.

CMV probably spreads through the body in lymphocytes or mononuclear cells to the lungs, liver, GI tract, eyes, and central nervous system, where it commonly produces inflammatory reactions.

Most patients with CMV infection have mild, nonspecific complaints or none at all, even though antibody titers indicate infection. In these patients, the disease usually runs a self-limiting course. However, immunocompromised patients and those receiving immunosuppressants may develop pneumonia or other secondary infections. In patients with acquired immunodeficiency syndrome (AIDS), disseminated CMV infection may cause chorioretinitis (resulting in blindness), colitis, encephalitis, abdominal pain, diarrhea, or weight loss. Infected infants ages 3 to 6 months usually appear asymptomatic but may develop hepatic dysfunction, hepatosplenomegaly, spider angiomas, pneumonitis, and lymphadenopathy. (See CMV infection in immunosuppressed patients.)