Chapter 18 Cytomegaloviral Infection
PATHOPHYSIOLOGY
Cytomegalovirus (CMV) is the leading cause of congenital viral infections in North America. A number of related strains of CMV exist. The virus is a member of the herpes family. CMV is probably transmitted through direct person-to-person contact with body fluids or tissues, including urine, blood, saliva, cervical secretions, semen, and breast milk. The period of incubation is unknown. The following are estimated incubation periods: after delivery, 3 to 12 weeks; after transfusion, 3 to 12 weeks; after transplantation, 4 weeks to 4 months. The urine often contains CMV months to years after infection. The virus can remain dormant in individuals and be reactivated. Currently, no immunizations exist to prevent infection with the virus.
Three types of CMV infection exist:
1. Congenital—acquired transplacentally in utero. The likelihood of congenital infection and the extent of the disease in the newborn depend on maternal immune status. Approximately 30% to 40% of infants born to women experiencing a primary (first) CMV illness during pregnancy will have clinical disease at birth. With recurrent maternal infection, (i.e., CMV infection that occurs repeatedly, leading to preconceptual immunity), the risk of transmission to the fetus is lower, ranging from 0.5% to 1.5%. Most of these infants appear normal at birth. The most severe form of congenital infection is referred to as cytomegalic inclusion disease.
2. Acute acquired—acquired anytime during or after birth through adulthood. Symptoms resemble those of mononucleosis (malaise, fever, pharyngitis, splenomegaly, petechial rash, respiratory symptoms). Infection is not without sequelae, especially in young children it can result from transfusions.
3. Generalized systemic disease—occurs in individuals who are immunosuppressed, especially if they have undergone organ transplantation. Symptoms include pneumonitis, hepatitis, and leukopenia, which can occasionally be fatal. Previous infection does not produce immunity and may result in reactivation of the virus.
INCIDENCE
1. Among live births, 0.4% to 2.5% of infants have congenital infection.
2. Premature infants are affected more often than full-term infants.
3. Of infected infants, 10% are symptomatic at birth; 90% suffer long-term sequelae (e.g., deafness, mental retardation, or ocular abnormalities).
4. Of severely infected infants, 4% to 30% die by 3 months of age; the remaining 60% to 75% will have some form of intellectual impairment or developmental delay.
5. Approximately one third of infected infants are normal in late childhood.
6. Prevalence of CMV infection is approximately 80% in children younger than 2 years of age who attend child care centers.
7. Seroprevalence of CMV approximates 50% in young adults of middle-upper socioeconomic status.
8. Incidence is higher in lower socioeconomic groups.
9. Of susceptible women, the seroconversion rate during pregnancy is 0.7% to 4.1%.
10. Both sexes are equally susceptible to infection and morbidity from CMV.
CLINICAL MANIFESTATIONS
In the newborn period, an infant infected with CMV is usually asymptomatic. Onset of symptoms from congenitally acquired infection can occur immediately after birth or as late as 12 weeks after birth.
There are no predictable indicators, but the following symptoms are common:
3. Neonatal jaundice; direct hyperbilirubinemia
4. Microcephaly with periventricular calcifications
5. Intrauterine growth retardation
