Information about CMV for Clinicians and Others in Healthcare Settings
General Information
Cytomegalovirus, or CMV, is found throughout all geographic locations
and socioeconomic groups and infects between 50% and 80% of adults in the
United States by 40 years of age. In the United States, 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 problem.
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 and bone marrow transplant recipients and persons 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 (which causes chickenpox), and Epstein-Barr virus
(which causes infectious mononucleosis). These viruses share a characteristic ability to remain
dormant within the body for life. Initial CMV infection, which may cause few symptoms,
is always followed by a prolonged, in apparent 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 may reactivate the virus from the latent or
dormant state.
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
Transmission of CMV occurs from person to person. Infection requires close
contact with a person excreting the virus in their saliva, urine, or other body
fluids. CMV can be sexually transmitted and can also be transmitted via
breast milk, transplanted organs, and occasionally 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 often transmitted through infected body 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 interacting with children and handling items like diapers.
Simple hand washing with soap and water is effective in removing the virus from the
hands. Pregnant women should also be counseled to avoid direct contact with the saliva of young
children through behaviors such as kissing on the lips.
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.
General screening of 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.
Circumstances in Which CMV Infection Could Be a Problem
Pregnancy
The incidence of primary (or first) CMV infection in pregnant women in the United States varies from
1% to 4%. 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 symptomatic 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 problems.
These risks are highest among 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 only 10% 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 approximately 1%, and significant illness or abnormalities among
these infants is infrequent.
CMV 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, unless the infant is very premature. In these cases, the
physician and mother must weigh the potential risk of transmitting CMV through breast milk
against the known benefits of breast-feeding.
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 or complications.
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).
- Avoid direct contact with the saliva of young children through behaviors such as kissing on the lips,
sharing food, drinks, or utensils.
- 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.
- If a woman is concerned about congenital CMV, laboratory testing for antibody
to CMV can be performed to determine if a women has already had CMV infection. A pregnant woman who
does not have CMV antibodies should be especially attentive to good hygiene.
- Recovery of CMV from the cervix or urine of women at or before the time of delivery does
not warrant a cesarean section.
- In most cases the demonstrated benefits of breast-feeding outweigh the minimal risk
of acquiring CMV from the breast-feeding mother. For very premature
infants, physicians and mothers should take into account the potential risk of transmitting CMV
when making decisions about breast-feeding.
- There is no need to either screen for CMV or exclude CMV-excreting children from schools or institutions where pregnant women work because the virus is frequently found in many healthy children
and adults.
People Who Work with Infants and Children
Most 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 aboutthe 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 and the
lower amount of personal contact in the health care setting.
Recommendations for individuals providing care for infants and children include the following:
- Female employees should be educated concerning CMV, its transmission,
and hygienic practices, such as hand washing, which minimize the risk of infection.
- Non-pregnant women of childbearing age working with infants and children
should not routinely be transferred to other work situations to avoid CMV infection.
- Pregnant women working with infants and children should be informed of the risk of
acquiring CMV infection and the possible effects on the unborn child and of appropriate prevention
strategies.
- Routine laboratory testing for CMV antibody in female workers is not currently recommended.
However, female workers who are pregnant or planning a pregnancy should be informed that a CMV antibody test
can help them assess their risk. Whenever possible, pregnant women who test CMV
negative (do not have CMV antibodies) should consider working in a setting
with less exposure to young children.
Immunocompromised Patients
Primary 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.
Diagnosis of CMV Infection in Adults
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 normally persist in the body for the lifetime of
that individual. A number of laboratory tests that detect CMV antibodies 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, so the need for testing should be evaluated on a case-by-case basis.
Diagnosis of Congenital CMV in infants?
A newborn has congenital CMV if the virus can be found in their urine, saliva, or blood during the first 3 weeks after birth. Rather than detecting antibodies, tests must identify the virus itself. Congenital CMV cannot be diagnosed if the baby is tested more than 3 weeks after birth, since he or she could have been infected after birth and so would not be at risk for disabilities. If the baby has congenital CMV, you should have his or her hearing and vision tested regularly. Most CMV-infected babies grow up with normal health, but if the child has delayed hearing or vision problems, early detection can help his or her development.
Serologic Testing
The enzyme-linked immunosorbent assay (or ELISA) is the most commonly available serologic test for measuring
antibody to CMV. 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.
Recently, IgG avidity assays, which measure antibody maturity, have been shown in most cases
to reliably identify primary CMV infection. These assays may be used in conjunction
with IgG and IgM assays, but are not yet commercially available in the United States.
Treatment
No treatment currently exists for CMV infection in the healthy individual. Ganciclovir treatment
is used for patients with depressed immunity who have either sight-related or life-threatening
illnesses. There is some evidence that ganciclovir may prevent hearing loss in children
with congenital CMV. However, ganciclovir can have serious side effects and was only tested in
children with sever congenital CMV disease. Parents and doctors should weigh the
benefits and risks to determine whether to treat children with symptomatic
congenital CMV. Vaccines are still in the research and development stage. A recent study suggest that
CMV hyperimmune globulin may reduce the risk of congenital infection and disease when given to mothers
experiencing a primary CMV infection. However, these results have not yet been confirmed by other
studies.
Guidelines
American College of Obstetricians and Gynecologists (ACOG). Perinatal viral and parasitic infections. Washington (DC): ACOG; 2000 Sep. 13 (ACOG practice bulletin; no. 20).
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