Congenital cytomegalovirus

Key Points

Cytomegalovirus (CMV) is the most common source of congenital infection in newborns and is a leading cause of hearing loss and intellectual disability in the United States.¹ As a result of its substantial disease burden, congenital CMV is associated with an estimated $1 billion to $2 billion in direct economic costs each year.² However, there has been limited progress in developing interventions to prevent or treat CMV infection. Researchers across disciplines are striving to better understand the epidemiology of congenital CMV, improve diagnostic tools, develop new treatments, and explore interventions for preventing infection and improving outcomes for infected infants.

BACKGROUND

CMV is a member of the herpesvirus family, which includes other well-known viruses such as the herpes simplex viruses (HSV), varicella-zoster virus, and Epstein-Barr virus. As a group, these DNA viruses are protein enveloped and share characteristics of latency and reactivation.³ It is not uncommon for re-infection with another CMV strain to occur in a previously infected host. As with most enveloped viruses, CMV is susceptible to inactivation by soap, heat, disinfectant, and dehydration.³

CMV can be transmitted between adults or adolescents through sex or kissing, from child to child or from child to adult through direct contact with bodily fluids such as urine or saliva, and through vertical transmission from mother to child in utero (causing congenital CMV), during birth, or through breast feeding.¹ CMV transmission through blood transfusion or organ transplantation from infected donors can also occur.

Individuals with normal immune systems usually do not experience symptoms from a primary CMV infection.¹ When symptoms do occur, they tend to be mild and flu-like. CMV infection can cause more severe symptoms, however, in fetuses, in HIV-infected individuals, and in organ transplant recipients who are on immunosuppressive therapies.

CMV INFECTION IN PREGNANT WOMEN

Primary CMV infections occur in 1% to 4% of seronegative pregnant women.^5,6 Each year in the United States, an estimated 27,000 pregnant women experience primary CMV infection and are thus at high risk of giving birth to a child with congenital CMV.⁵ Of these women, approximately one-third transmit CMV to the fetus. Prolonged contact with young children, especially among parents and childcare providers, is a risk factor for primary CMV infections during pregnancy.⁷

In mothers who are seropositive before conception, approximately 1% will transmit CMV infection to the fetus as a result of recurrent maternal infection (ie, reactivation or re-infection with another strain of the virus).⁷ Because many women are seropositive before pregnancy, more congenital infections occur as a result of a recurrent rather than primary maternal infection.⁸

There are 3 time periods during which mother-to-child transmission can occur: in utero, during birth, and after birth. However, permanent disability only occurs in association with in utero infection.⁹ Such disability can result from maternal infection during any point in the pregnancy, but more severe disabilities are usually associated with maternal infection during the first trimester.⁹