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Clinical Features

For most healthy persons who acquire CMV after birth, there are few symptoms and no long-term health consequences. Some persons who acquire CMV infection may experience a mononucleosis-like syndrome with prolonged fever and a mild hepatitis. Once a person becomes infected, the virus remains alive, but usually dormant, within their body for life. Disease from reactivation of CMV infection rarely occurs unless the person's immune system is suppressed due to therapeutic drugs or disease. Therefore, for the vast majority of 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 or during delivery, and
  2. Immunocompromised persons, such as organ and bone marrow transplant recipients and persons infected with human immunodeficiency virus (HIV).

Characteristics of the Virus

CMV is a herpesvirus. This group of viruses include herpes simplex virus types 1 and 2, varicella-zoster virus, and Epstein-Barr virus. These viruses share a characteristic ability to remain dormant within the body for life. After initial infection, which may cause few symptoms, CMV becomes latent, residing in cells without causing detectable damage or clinical illness. Severe impairment of the body's immune system by medication or disease may allow the virus to reactivate from the latent or dormant state and become symptomatic.

People who are infected with CMV sometimes shed the virus in body fluids, such as urine, saliva, blood, tears, semen, and breast milk. The shedding of virus may take place intermittently, without any detectable signs, and without causing symptoms.

Transmission and Prevention

CMV is transmitted by direct person-to-person contact with a person excreting the virus in their saliva, urine, or other body fluids; contact with infectious body fluids (e.g., urine on a diaper); or contact with fomites (e.g., a child’s toy that has infectious virus on it). CMV can be sexually transmitted and can also be transmitted via transplanted organs and blood transfusions.

CMV can be transmitted to infants via contact with maternal genital secretions during delivery or through breast milk. However, infections that occur through these routes usually result in little or no clinical illness in the infant unless the infant is very premature.

There are no recommendations against breastfeeding by mothers who are shedding CMV. The potential benefits of human milk versus the risk of CMV transmission should be considered when making a decision about breastfeeding of very low birth weight infants (birth weight <1500 g) by mothers known to be CMV-seropositive. Preterm infants <1000g birth weight and <30 weeks gestational age may be at high risk of symptomatic CMV infection and may present a sepsis-like syndrome. Freezing and pasteurization of breast milk can decrease the risk of transmission; however, freezing does not eliminate the risk of transmission.

Healthy infants and children who acquire CMV after birth generally have few, if any, symptoms or complications from the infection.

Although the virus is not highly contagious, it has been shown to spread among household members and among young children in day care centers. The virus can be transmitted through infected body fluids that come in contact with hands and then are passed to the nose or mouth of a susceptible person.

Because infections among healthy persons, including infants and young children, are common and typically asymptomatic, efforts to prevent transmission among healthy children are not necessary. Screening of children for CMV infection is not recommended, and infected children should not be excluded from school or other settings. Standard hygiene practices are advised for all persons caring for children.

Congenital CMV infections can only be prevented by preventing CMV infection in pregnant women. Pregnant women can take steps that may reduce their exposure to CMV and other infections that may pose a risk. (See general information on Prevention.)

Standard precautions in healthcare settings are adequate for preventing transmission of CMV between patients and staff. Routine screening of patients for CMV infection is not recommended. Also see general information on Transmission.

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Experimental Vaccine Shows Promise in Preventing Cytomegalovirus Infection
March 19, 2009 Press Release from the National Institutes of Health

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