Cytomegalovirus (CMV) is a ubiquitous herpes virus with the capacity to cause a diverse array of clinical syndromes. It is composed of a linear, double-stranded DNA genome and is not considered highly contagious. However, any person infected with CMV, be it dormant or an active infection can transmit the virus to another person. The virus can be carried in body fluids such as urine, tears, saliva, blood, semen, cervical secretions and breast milk. Although primary CMV infection is often asymptomatic in the immunologically competent host, both primary infection and reactivation may produce severe disease in those who are immune-compromised.
Since effective control of CMV infection requires intact cell-mediated immunity, the population at highest risk for invasive CMV disease includes neonates, allograft recipients and individuals infected with HIV. Moreover, it is frequently transmitted from mother to child, either in utero or during the perinatal phase. Prenatal transmission often results in severe disturbance of development and diseases that may manifest at birth, such as thrombocytopenia, hepatitis, splenomegaly, and microcephaly. The frequent late sequel is hearing loss and mental retardation.
CMV infection is usually asymptomatic. In immunocompetent individuals, the symptomatic disease usually manifests as mononucleosis syndrome causing a febrile illness with splenomegaly, impaired liver function and abnormal lymphocytes in the blood, but without characteristic pharyngitis and lymphadenopathy. CMV is one of the commonest congenital infections. Those children born with cytomegalic inclusion disease have a poor prognosis. The sensorineural hearing loss is the most frequent long-term consequence and in many cases does not become clinically apparent until later childhood.
CMV is one of the most important pathogens that infect solid organ transplant recipients due to the immunosuppression and is associated with increased morbidity and mortality. Patients receiving T-celI depleting therapies are at the highest risk.
Positive lgG results in the absence of IgM antibodies that are most often indicative of past Cytomegalovirus infection and do not necessarily assure protection from future infection with CMV. LGM positive status is indicative of a primary or recurrent infection. IgM antibodies to CMV can persist for 2 to 9 months after the initial infection. Not all patients with reactivated CMV infection will have detectable levels of IgM antibodies. Positive IgM results in neonates have a high probability of being an indication of congenital or neonatal infection.