Cytomegalovirus (CMV) is notable among Human Herpesvirus because it almost never causes clinical disease in immunocompetant hosts. This is despite the fact that almost the entire adult population is seropositive for the virus. Only three groups of people are at risk for clinical disease. They are: (1) unborn children born to women who contract CMV for the first time or have a reactivation of infection during pregnancy. A small percentage (7-10%) of these babies will have symptoms or will develop disabilities including mental retardation and hearing loss; (2) Organ transplant patients or patients using immunosuppressive drugs; and (3) Patients with immune deficiency diseases.
CMV is primarily spread through close personal contact. CMV is present in all body secretions including urine, saliva, feces, blood, breast milk, semen, and cervical secretions. As a result, CMV can be transmitted in any way that involves passing any body secretions. This includes sexual contact, blood transfusion, organ transplant, and breast feeding.
In organ transplant patients, CMV may manifest itself as fever, leukopenia, hepatitis, pneumonitis, esophagitis, gastritis, colitis, and retinitis. Disease is more likely and more severe if the infection is primary. The transplant organ is often targeted for CMV infection. CMV pneumonia occurs in 15% of bone marrow transplant recipients. Of these cases, 84% are fatal.
CMV induced retinitis is the leading cause of blindness among AIDS patients. CMV infection is ubiquitous among AIDS patients and contributes to death by suppressing the immune system. It does this by further depleting T lymphocyte cells.