CMV infection is worldwide.
Many serological surveys have shown CMV to be present in 42–100% of the people depending on socioeconomic condition. In developing countries, infection of children is most common with a seroprevalence for CMV to be 100% very early in child-hood. In developed countries, infection of the young adults is more common; more than 50% of young adults are seropositive in many developed countries.
Humans are the natural hosts. An infected human is the only reservoir of CMV infection. No animal reservoirs are pres-ent for this virus. Cytomegaloviruses are found in the urine, blood, saliva, tears, throat swab, stool, semen, milk, amniotic fluid, cervical and vaginal secretions, and tissue obtained for transplantation.
Saliva, tears, urine, and breast milk are the common sources of infection for baby or child. Cervical secretions are the source of transmission of infection to neonates. Blood, organ graft, and semen are the other sources of infection in adult popula-tion. Transmission of CMV occurs in a variety of ways:
· Early in life, infection is transmitted to infants through the placenta, through infected birth canal, and also through breast milk.
· Infection to young children is most commonly transmitted by saliva.
· In adults, infection is transmitted sexually through semen and cervical secretions.
· Infection is also transmitted through the blood transfusion and organ transplantation.
CMV causes latent infection; hence reactivation may result in disease in patients who are immunocompromised. These patients include those with HIV and those receiving organ and bone marrow transplantation. Immunodeficiency caused by antineoplastic compounds and ionizing radiation may also cause reactivation of CMV infection.