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 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 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 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 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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