What is Cytomegalovirus (CMV)?
Cytomegalovirus (CMV) is a virus that can be transmitted to a developing child before birth. CMV infection is usually harmless and rarely causes illness. For most healthy persons who acquire CMV after birth, there are few symptoms and no long-term health consequences. Once a person becomes infected, the virus remains alive, but usually dormant within that person’s body for life. There are two different types of infection: primary CMV and recurrent CMV infection. Primary infection can cause more serious problems in pregnancy than recurrent infection can. However, if a person’s immune system is seriously weakened in any way, the virus can become active and cause CMV disease. For the majority of people who have CMV infection, it is not a serious problem.
What are the symptoms of CMV?
Most children and adults who are infected with CMV do not develop symptoms, whereas others may experience the following symptoms three to twelve weeks after exposure:
- Swollen glands
- Exhausted or run down
What are characteristics of CMV?
CMV is a member of the herpes virus group that is characterized by the ability to remain dormant within the body over a long period. Infectious CMV may be shed in bodily fluids (urine, saliva, blood, tears, semen, and breast milk) intermittently, without any detectable signs and without symptoms.
How common is CMV?
- Infects between 50% and 85% of adults in the United States by 40 years of age
- Is more widespread in developing countries and in areas of lower socioeconomic conditions
- Is higher among the following risk groups:
- babies in utero
- people who work with children
- immunocompromised persons, such as organ transplant recipients and persons infected with human immunodeficiency virus (HIV)
How is CMV spread?
Transmission of CMV occurs from person to person and is not associated with food, water, or animals. CMV is not highly contagious but has been shown to spread in households and among young children in day care centers. The infection is spread through close, intimate contact with a person excreting the virus in their saliva, urine, breast milk or other bodily fluids.
How is CMV diagnosed?
Most CMV infections are rarely diagnosed because the virus usually produces few, if any, symptoms. However, people who have had CMV develop antibodies to the virus which remain in their body for the rest of their life. A blood sample can test for the CMV antibody, followed by another blood sample within two weeks. The virus can also be cultured from specimens obtained from urine, throat swabs, and tissue samples. Laboratory tests to culture the virus are expensive and not widely available.
If a pregnant woman is diagnosed with the CMV infection, there are a few ways that the fetus can be checked for infection. Amniocentesis can be done to check fetal fluids or blood for signs of infection. Symptoms that could signify possible infection include low amniotic fluid levels, intrauterine growth restriction, and enlarged tissues in the brain. Once the baby is born, testing can be done by saliva, urine, or blood.
What is the treatment for CMV?
Maternal CMV infections may be treated with one of two drugs that are used in severe situations of CMV infection. There are no treatments for prenatal or postnatal therapy of the infection. Vaccines for treatment are still in the research and developmental stages.
How can CMV be prevented?
Transmission of cytomegalovirus is often preventable because it is most often transmitted through infected bodily fluids that come in contact with hands and then are absorbed through the nose or mouth of a susceptible person. People who interact with children should use safe hygiene practices including good hand washing and wearing gloves when changing diapers. Hand washing with soap and water is effective in preventing the spread of CMV.
How does CMV affect pregnancy?
Pregnant women who are healthy are not at special risk for disease from CMV infection. In fact, the incidence of primary maternal CMV infection in pregnant women in the United States varies from 0.7% to 4%. Pregnant women who are infected with CMV rarely have symptoms, but rather their developing baby may be at risk for congenital (meaning from birth) CMV disease. CMV is the most common cause of congenital viral infection in the United States. The transmission rate to the fetus is between 24-75% according to the Organization of Teratology Information Service (OTIS), with an average transmission rate of 40%. Of the 40% of babies who become infected, only 10% show signs of congenital CMV after primary maternal infection. For women who have been infected at least 6 months prior to conception, the rate of newborn CMV infection is about 1%, and these infants appear to have no significant illness or abnormalities.
The following potential problems can occur for infants who are infected from their mothers before (during pregnancy) birth:
- Moderate enlargement of the liver and spleen
- 80-90% suffer from complications within the first few years of life including hearing loss, vision impairment, and varying degrees of mental retardation.
- 5-10% will present with no symptoms at birth but will develop varying degrees of hearing and mental or coordination problems.
When CMV is transmitted at the time of delivery from contact with genital secretions or later in infancy through breast milk, these infections usually result in few, if any, symptoms or complications.
What are some recommendations for pregnant women regarding CMV infection?
- Throughout your pregnancy practice good personal hygiene, including hand washing with soap and water
- If you develop a mononucleosis-like illness, you should be checked for CMV infection
- Refrain from sharing food, eating utensils and drinking utensils with anyone.
- Your doctor can test the CMV antibodies to determine if you have already had CMV infection.
- Breastfeeding benefits outweigh the minimal risk of transmitting CMV
What are some recommendations for individuals who care for infants and children regarding CMV infection?
Most healthy people working with infants and children are not at risk of CMV infection. However, women of child-bearing age who previously have not been infected with CMV still have a potential risk of passing CMV to their babies in utero. CMV is commonly transmitted among young children. Since CMV is transmitted through contact with infected bodily fluids, including urine and saliva, child care providers (including day care workers, special education teachers, and therapists) should be educated about CMV infection and practice preventive measures. Susceptible non-pregnant women working with infants and children should not routinely be transferred to other work situations. Routine laboratory testing for the CMV antibody in female workers is not recommended, but can be performed to determine their immunity status.
Compiled using information from the following sources:
Organization of Teratology Information Services, http://otispregnancy.org/pdf/cytomegalovirus.pdf
Williams Obstetrics Twenty-Second Ed. Cunningham, F. Gary, et al, Ch. 58.
American Pregnancy Association, http://www.americanpregnancy.org