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Cytomegalovirus, or CMV, is found universally throughout all geographic
locations and socioeconomic groups, and infects between 50% and 85% of
adults in the United States by 40 years of age. CMV is also the virus most
frequently transmitted to a developing child before birth. CMV infection
is more widespread in developing countries and in areas of lower
socioeconomic conditions. For most healthy persons who acquire CMV
after birth there are few symptoms and no long-term health
consequences. Some persons with symptoms 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 that
person's body for life. Recurrent disease 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
However, CMV infection is important to certain high-risk groups. Major
areas of concern are (1) the risk of infection to the unborn baby during
pregnancy, (2) the risk of infection to people who work with children, and
(3) the risk of infection to the immunocompromised person, such as organ
transplant recipients and persons infected with human immunodeficiency
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CMV is a member of the herpesvirus group, which includes herpes simplex
virus types 1 and 2, varicella-zoster virus (which causes chickenpox), and
Epstein-Barr virus (which causes infectious mononucleosis). These viruses
share a characteristic ability to remain dormant within the body over a
long period. Initial CMV infection, which may have few symptoms, is always
followed by a prolonged, inapparent infection during which the virus
resides in cells without causing detectable damage or clinical illness.
Severe impairment of the body's immune system by medication or disease
consistently reactivates the virus from the latent or dormant state.
Infectious CMV may be shed in the bodily fluids of any previously
infected person, and thus may be found in urine, saliva, blood, tears,
semen, and breast milk. The shedding of virus may take place
intermittently, without any detectable signs, and without causing
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Transmission of CMV occurs from person to person. Infection
requires close, intimate contact with a person excreting the virus in
their saliva, urine, or other bodily fluids. CMV can be sexually
transmitted and can also be transmitted via breast milk, transplanted
organs, and rarely from blood transfusions.
Although the virus is not highly contagious, it has been shown to
spread in households and among young children in day care centers.
Transmission of the virus 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.
Therefore, care should be taken when handling children and items like
diapers. Simple hand washing with soap and water is effective in removing
the virus from the hands.
CMV infection without symptoms is common in infants and young children;
therefore, it is unjustified and unnecessary to exclude from school or an
institution a child known to be infected. Similarly, hospitalized patients
do not need separate or elaborate isolation precautions.
Screening children and patients for CMV is of questionable value. The
cost and management of such procedures are impractical. Children known to
have CMV infection should not be singled out for exclusion, isolation, or
special handling. Instead, staff education and effective hygiene practices
are advised in caring for all children.
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The incidence of primary (or first) CMV infection in pregnant women in the United
States varies from 1% to 3%. Healthy pregnant women are not at special risk
for disease from CMV infection. When infected with CMV, most women have no symptoms
and very few have a disease resembling mononucleosis. It is their developing
unborn babies that may be at risk for congenital CMV disease. CMV remains the
most important cause of congenital (meaning from birth) viral infection in the
United States. For infants who are infected by their mothers before birth, two
potential problems exist:
- Generalized infection may occur in the infant, and symptoms may range
from moderate enlargement of the liver and spleen (with jaundice) to fatal
illness. With supportive treatment most infants with CMV disease usually
survive. However, from 80% to 90% will have complications within the first
few years of life that may include hearing loss, vision impairment, and
varying degrees of mental retardation.
- Another 5% to 10% of infants who are infected but without symptoms at
birth will subsequently have varying degrees of hearing and mental or coordination
However, these risks appear to be almost exclusively
associated with women who previously have not been infected with CMV
and who are having their first infection with the virus during
pregnancy. Even in this case, two-thirds of the infants will not become
infected, and only10% to 15% of the remaining third will have symptoms at
the time of birth. There appears to be little risk of CMV-related
complications for women who have been infected at least 6 months prior to
conception. For this group, which makes up 50% to 80% of the women of
child-bearing age, the rate of newborn CMV infection is 1%, and these
infants appear to have no significant illness or abnormalities.
The virus can also be transmitted to the infant at delivery from
contact with genital secretions or later in infancy through breast milk.
However, these infections usually result in little or no clinical illness
in the infant.
To summarize, during a pregnancy when a woman who has never had CMV
infection becomes infected with CMV, there is a potential risk that
after birth the infant may have CMV-related complications, the most common
of which are associated with hearing loss, visual impairment, or
diminished mental and motor capabilities. On the other hand, infants and
children who acquire CMV after birth have few, if any, symptoms
Recommendations for pregnant women with regard to CMV infection:
- Throughout the pregnancy, practice good personal hygiene, especially handwashing
with soap and water, after contact with diapers or oral secretions (particularly
with a child who is in day care).
- Women who develop a mononucleosis-like illness during pregnancy should
be evaluated for CMV infection and counseled about the possible risks to
the unborn child.
- Laboratory testing for antibody to CMV can be performed to determine if
a women has already had CMV infection.
- Recovery of CMV from the cervix or urine of women at or before the time
of delivery does not warrant a cesarean section.
- The demonstrated benefits of breast-feeding outweigh the minimal risk
of acquiring CMV from the breast-breeding mother.
- There is no need to either screen for CMV or exclude CMV-excreting children
from schools or institutions because the virus is frequently found in many
healthy children and adults.
healthy people working with infants and children face no special risk from
CMV infection. However, for women of child-bearing age who previously have
not been infected with CMV, there is a potential risk to the developing
unborn child (the risk is described above in the Pregnancy section).
Contact with children who are in day care, where CMV infection is commonly
transmitted among young children (particularly toddlers), may be a source
of exposure to CMV. Since CMV is transmitted through contact with infected
body fluids, including urine and saliva, child care providers (meaning day
care workers, special education teachers, therapists, as well as mothers)
should be educated about the risks of CMV infection and the precautions
they can take. Day care workers appear to be at a greater risk than
hospital and other health care providers, and this may be due in part to
the increased emphasis on personal hygiene in the health care setting.
Recommendations for individuals providing care for infants and children:
- Female employees should be educated concerning CMV, its transmission,
and hygienic practices, such as handwashing, which minimize the risk of
- Susceptible nonpregnant women working with infants and children should
not routinely be transferred to other work situations.
- Pregnant women working with infants and children should be informed of
the risk of acquiring CMV infection and the possible effects on the unborn
- Routine laboratory testing for CMV antibody in female workers is not recommended,
but can be performed to determine their immune status.
Primary (or the initial) CMV infection in the immunocompromised patient can
cause serious disease. However, the more common problem is the reactivation
of the dormant virus. Infection with CMV is a major cause of disease and death
in immunocompromised patients, including organ transplant recipients, patients
undergoing hemodialysis, patients with cancer, patients receiving immunosuppressive
drugs, and HIV-infected patients. Pneumonia, retinitis (an infection of the
eyes), and gastrointestinal disease are the common manifestations of disease.
Because of this risk, exposing immunosuppressed patients to outside sources
of CMV should be minimized. Whenever possible, patients without CMV infection
should be given organs and/or blood products that are free of the virus.
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Most infections with CMV are not diagnosed because the virus usually
produces few, if any, symptoms and tends to reactivate intermittently
without symptoms. However, persons who have been infected with CMV develop
antibodies to the virus, and these antibodies persist in the body for the
lifetime of that individual. A number of laboratory tests that detect
these antibodies to CMV have been developed to determine if infection has
occurred and are widely available from commercial laboratories. In
addition, the virus can be cultured from specimens obtained from urine,
throat swabs, and tissue samples to detect active infection.
CMV should be suspected if a patient:
- has symptoms of infectious mononucleosis but has negative test results
for mononucleosis and Epstein Barr virus, or,
- shows signs of hepatitis, but has negative test results for hepatitis
A, B, and C.
For best diagnostic results, laboratory tests for CMV antibody should
be performed by using paired serum samples. One blood sample should be
taken upon suspicion of CMV, and another one taken within 2 weeks. A virus
culture can be performed at any time the patient is symptomatic.
Laboratory testing for antibody to CMV can be performed to determine if
a woman has already had CMV infection. However, routine laboratory testing
of all pregnant women is costly and the need for testing should therefore
be evaluated on a case-by-case basis.
The enzyme-linked immunosorbent
assay (or ELISA) is the most commonly available serologic test for
measuring antibody to CMV. The result can be used to determine if acute
infection, prior infection, or passively acquired maternal antibody in an
infant is present. Other tests include various fluorescence assays,
indirect hemagglutination, and latex agglutination.
An ELISA technique for CMV-specific IgM is available, but may give
false-positive results unless steps are taken to remove rheumatoid factor
or most of the IgG antibody before the serum sample is tested. Because
CMV-specific IgM may be produced in low levels in reactivated CMV
infection, its presence is not always indicative of primary infection.
Only virus recovered from a target organ, such as the lung, provides
unequivocal evidence that the current illness is caused by acquired
CMV infection. If serologic tests detect a positive or high titer of
IgG, this result should not automatically be interpreted to mean that
active CMV infection is present. However, if antibody tests of paired
serum samples show a fourfold rise in IgG antibody and a significant level
of IgM antibody, meaning equal to at least 30% of the IgG value, or virus
is cultured from a urine or throat specimen, the findings indicate that an
active CMV infection is present.
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Currently, no treatment exists for CMV infection in the healthy
individual. Antiviral drug therapy is now being evaluated in infants.
Ganciclovir treatment is used for patients with depressed immunity who
have either sight-related or life-threatening illnesses. Vaccines are
still in the research and development stage.
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