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Clinical Overview

For most healthy people who acquire cytomegalovirus (CMV) after birth, there are few symptoms and no long-term health consequences. Some people who acquire CMV infection may experience a mononucleosis-like condition with prolonged fever and hepatitis. Once a person becomes infected, the virus remains latent and may reactivate occasionally. Disease from reactivation of CMV infection rarely occurs unless the person’s immune system is suppressed due to therapeutic drugs or disease.

For most people, CMV infection is not a serious health problem. However, certain groups are at high risk for serious complications from CMV infection:

  1. Infants infected in utero (congenital CMV infection)
  2. Very low birth weight and premature infants
  3. People with compromised immune systems, such as from organ and bone marrow transplants, and people infected with human immunodeficiency virus (HIV)

Characteristics of the Virus

CMV is a member of the herpesvirus family, which includes herpes simplex virus types 1 and 2, varicella-zoster virus, and Epstein-Barr virus. These viruses share a characteristic ability to establish lifelong latency. After initial infection, which may cause few symptoms, CMV becomes latent, residing in cells without causing detectable damage or illness.

Transmission

CMV infects people of all ages. In the United States; nearly one in three children are already infected with CMV by age five. By the age of 40, over half of adults have been infected with CMV, most with no signs or symptoms.

CMV is transmitted by direct contact with infectious body fluids, such as urine, saliva, blood, tears, semen, and breast milk. CMV can be transmitted sexually and through transplanted organs and blood transfusions. 

CMV can be transmitted to infants through contact with the mother’s genital secretions during delivery or through breast milk. Healthy infants and children who acquire CMV after birth generally have few, if any, symptoms or complications from the infection. Women who are infected with CMV can still breastfeed full-term infants. Although the virus is not highly contagious, it has been shown to spread among household members and young children in daycare centers.

Childcare workers

People who have frequent contact with young children may be at greater risk of CMV infection  because young children are a common source of CMV. By the age of five months, one in three children has been infected with CMV, but usually does not have symptoms. CMV can be present in a child’s body fluids for months after they become infected. Regular hand washing, especially after contact with body fluids of young children, is commonly recommended to avoid spread of infections, including CMV.

Pregnant women

In the United States, nearly half of women have already been infected with CMV before their first pregnancy. Of women who have never had a CMV infection, it is estimated that 1 to 4% of them will be infected during pregnancy.

A woman who has a primary CMV infection during pregnancy is more likely to pass CMV to her fetus than a women who has a subsequent infection during pregnancy. However, in the United States, 50 to 75% of congenital CMV infections occur among infants born to mothers who were infected with CMV before they became pregnant.

Routine screening for primary CMV infection during pregnancy is not recommended in the United States for several reasons. Most laboratory tests currently available to identify a first-time infection can be difficult to interpret.  Secondly, current tests cannot predict if the fetus may become infected or harmed by infection.  Thirdly, the lack of a proven treatment to prevent or treat infection of the fetus reduces the potential benefits of prenatal screening.

Very low birth weight and premature infants

There are no recommendations against breastfeeding by mothers who are CMV-seropositive. However, infants born <30 weeks gestational age and <1500g who acquire CMV from breast milk may be at risk of developing a late-onset sepsis-like syndrome. The potential benefits of human milk versus the risk of CMV transmission should be considered when making a decision about the breastfeeding of very premature babies by mothers known to be CMV-seropositive. Freezing and pasteurization of breast milk can decrease the risk of transmission; however, freezing does not eliminate the risk of transmission.

Diagnosing CMV

Primary CMV infections usually go unrecognized because most people are asymptomatic or have mild symptoms that are not unique to CMV. Primary CMV infection should be suspected if a pregnant woman:

  • Has influenza like symptoms (typically fever, fatigue, and headache) not attributable to another specific infection, such as infectious mononucleosis but has negative test results for Epstein-Barr virus;
  • Shows signs of hepatitis, but has negative test results for hepatitis A, B, and C; or
  • When imaging findings (ultrasound or the less frequently used MRI) are suggestive of fetal cytomegalovirus infection.

CMV may be detected by polymerase chain reaction (PCR) or viral culture of infected blood, urine, saliva, cervical secretions, or breast milk. Primary CMV infection can also be diagnosed using serologic testing if serum samples collected one to three months apart are available.

Seroconversion (1st sample IgG negative, 2nd sample IgG positive) is clear evidence for recent primary infection. However, diagnosis of CMV infection in a child less than one year old can be complicated by the presence of maternal CMV IgG. For more information, see Interpretation of Laboratory Tests.

Treatment and Management

No treatment is currently indicated for CMV infection in healthy people. Antiviral treatment is used for people with compromised immune systems who have either sight-related or life-threatening illnesses due to CMV infection. For congenital CMV treatment options, see Congenital CMV Infection.

Prevention

CMV is common in children and can be found in especially high amounts in young children’s saliva and urine. Avoiding contact with saliva and urine from young children might reduce the risk of CMV infection. Some examples of how to avoid contact include kissing children on the head rather than the lips and not sharing food or utensils with them, and washing hands after changing diapers. These cannot eliminate a person’s risk of catching CMV, but may lessen the chances of getting it.

Healthcare providers should follow standard precautions. Vaccines are still in the research and development stage.

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