extremely
common, occurring in 50-85% of all Americans by age 40
most
people never know that they have been exposed
a member
of the family of viruses called herpesvirus (it is not
oral or genital herpes)
can
cause birth defects if the fetus becomes involved, but involvement
is rare (1 to 3%)
can
cause severe disease in people with HIV or depressed immune
systems, such as retinitis, ulcers, and CNS diseases
is
most often transmitted through contact with saliva, semen,
vaginal
secretions, blood, urine and breast milk
GENERAL
INFORMATION 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. Rarely, some people 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 problem at all. 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 virus (HIV).
CHARACTERISTICS
OF THE VIRUS 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 symptoms.
TRANSMISSION
AND PREVENTION 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.
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 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. Although rare, CMV remains one of the
most important causes 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
problems. 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 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 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 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). 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. 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 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 infection. 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 child. Routine
laboratory testing for CMV antibody in female workers is not
recommended, but can be performed to determine their immune
status. Immunocompromised Patients 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.
DIAGNOSIS
OF CMV INFECTION 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 ofprimary 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.
TREATMENT
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.
DONOR
TESTING FOR CMV In order to detect if a person has been
exposed to CMV, a blood sample is tested for anti-bodies to
the virus. Two classes of antibodies are checked for, IgG and
IgM. The IgG class of antibody indicates if the individual has
ever been exposed to the virus in his or her lifetime and built
antibodies against the virus. If a person tests positive for
the IgM class of antibody it is an indicator of a recent or
current infection and indicates a higher likelihood of that
person shedding virus in body fluids at that time. There are
no donors used who check CMV IgM positive. By the time the initial
infection is over the IgM response will drop off and the person
will only show IgG anti-bodies indicating past infection. For
the above reasons it is suggested that if an individual is going
to expose themselves to body fluids such as semen that could
potentially have CMV, that they get checked, and only use such
specimens if they show evidence of past exposure by also showing
positive for the IgG anti-body to CMV. Persons testing negative
for exposure to the virus by testing IgG and IgM negative can
minimize their potential exposure risk by using only CMV IgG
negative donors. It is important to note that a positive ("reactive")
serum antibody titer to CMV indicates only that the individual
has been infected with the virus at some time in the past. Although
possible, the vast majority of these individuals are not shedding
CMV from any body fluid and are not highly infectious. Check with
your doctor, as many are of the opinion that it is of almost no concern.
We don't want to minimize it, but most people don't know what
CMV is until they read this, most will be exposed to CMV in
thier lives and never know it, and in real life nobody checks
their potential spouse for this virus.
