CMV causes (a) congenital CMV infection, (b) acquired CMV infection, (c) CMV infection in immunocompromised patients, and (d) CMV infection in immunocompetent adult hosts.
CMV is the most common viral cause of congenital infection. The infection is acquired by fetus by transmission of virus through placenta from mother’s blood. The infection can also be an ascending infection from the cervix of the mother during recurrence of infection. The congenital infection may be classi-fied as asymptomatic or symptomatic
Asymptomatic congenital CMV infection occurs in infants born to women who have preexisting immunity to CMV. These infants appear normal at birth but are at risk of developing growth retardation and other neurodevelopmental abnormali-ties during later stage of life.
Cytomegalic inclusion disease is the manifestation of the symptomatic congenital CMV infection, which usually occurs in women who acquire primary CMV infection during preg-nancy. The disease is characterized by microcephaly, intrace-rebral calcification, hepatosplenomegaly, and rash. Mental retardation and unilateral or bilateral hearing loss are the most common consequences of cytomegalic inclusion disease in adults. Approximately, 10% of affected infants show clinical evidence of disease at birth.
Acquired CMV infection occurs postnatally as follows:
Perinatal CMV infection: This condition usually occursfollowing exposure to infected genital secretions in the birth canal or to milk during breast feeding. Most perinatal infec-tions are asymptomatic. Some infants may manifest lymph-adenopathy, hepatitis, and pneumonitis. However, these patients do not show any neurological or neurodevelopmental complications.
CMV mononucleosis: CMV mononucleosis is a disease ofyoung adults acquired by person-to-person transmission. This condition is transmitted by blood transfusion or organ trans-plantation. Fever and severe malaise are typical symptoms. Clinically, it is difficult to distinguish CMV mononucleosis from EBV-induced mononucleosis.
Transfusion-acquired CMV infection: This conditionoccurs following transfusion of infected blood after an incubation period of 20–60 days. This condition is mostly asymptomatic. In symptomatic cases, clinical manifesta-tions of transfusion-acquired CMV are similar to CMV mononucleosis.
CMV is the most important opportunistic agent in immuno-compromised hosts, in whom it causes a variety of clinical syn-dromes. These include life-threatening intestinal pneumonitis, gastrointestinal diseases, retinitis, hepatitis, encephalitis, and varieties of other CMV syndromes. Patients receiving organ transplants are severely affected by the disease.
CMV produces mononucleosis syndrome, a condition similar to EBV-induced mononucleosis in immunocompetent adult hosts. CMV is a sexually transmitted disease. The infection is transmitted by contaminated genital secretions.