Cytomegalovirus

 

 

 

Epidemiology

 

CMV infects 0.5%-2.5% of newborns and is the most common viral cause of congenital defects. Up to 50% of adults in developed countries become infected with CMV, posing a serious problem as an opportunistic infection in immunocompromised patients.

 

 

Classification and Characteristics

 

CMV is a DNA virus belonging to the herpes family. Human CMV replicates only in human cells, including fibroblasts, epithelial cells, and macrophages.

CMV can establish latent infection in the bone marrow, in mononuclear leukocytes, and other cells.

 

 

 

 

Transmission and Infection

 

CMV may be found in most body fluids, including urine, blood, throat lavage, saliva, tears, breast milk, semen, stool, amniotic fluid, and vaginal secretions. It may also be found in transplants.

Congenital, oral and sexual routes, blood transfusion, and tissue transplantation are the major pathways of CMV transmission.

 

 

 

Pathogenicity and Virulence

 

CMV easily causes persistent and latent infections in mononucelar leukocytes and organs such as the heart and kidneys. These infections do not usually produce definable symptoms. Replication in ductal epithelial cells results in virus shedding in bodily fluids. CMV is highly cell-associated and is transmitted by infected cells.

 

 

 

Clinical Manifesations

 

Congenital infection

Approximately 10% of infected newborns show clinical evidence of disease, including microencephaly, intracerebral calcification, hepatosplenomegaly, and rash. Hearing loss and mental retardation are also common. Risks are highest for infants whose mothers acquired a primary CMV infection during pregnancy.

 

Perinatal Infection

Virus reactivation may occur during pregnancy, and neonates may acquire CMV infection during birth or from the milk. Healthy full-term infants do not normally manifest disease, while premature infants may develop pneumonia or hepatitis.

 

Child and Adult Infection

CMV is predominantly a sexually-transmitted disease in adults, with rates rising from 10-15% in adolescents to 50% by age 35. Most CMV infections are asymptomatic, though some patients develop a heterophile-negative mononucleosis syndrome. This is similar to EBV infection, but with less severe pharyngitis and lymphadenopathy.

 

Infection in Immunocompromised Patients

Cell-mediated immunity is responsible for resolving and controlling CMV infection, with limited role of antibody. Immunosupression may result in recurrence and severe presentation. CMV-induced pneumonia and pneumonitis is a serious and common outcome in immunosuppressed patients. Retinitis, encephalitis, colitis, and esophagitis may also develop.

 

 

Diagnosis

 

CMV may be diagnosed histologically by the presence of cytomegalic cells, which are 25-35 um in size and contain a dense, "owl's eye" basophilic intranuclear inclusion body. These cells may be found in any tissue and in the urine.

Serology, EIA, or PCR may also be used to diagnose CMV.

 

 

Treatment

Ganciclovir and foscarnet are useful in treating CMV infection, especially in immunocompromised patients. Both drugs inhibit the viral DNA polymerase. Valgancilovir (oral agent) can be used for maintenance.

CMV matching is important in transplant patients, as primary infection can be a serious problem in immunocompromised.