Page 336 - Review of Medical Microbiology and Immunology ( PDFDrive )

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CHAPTER 39 RNA Enveloped Viruses
rubella virus is present in the patient’s specimen and has
grown in the cell culture, no CPE will appear when the
culture is superinfected with an echovirus. The diagnosis
can also be made by observing a fourfold or greater rise in
antibody titer between acute-phase and convalescent-phase
sera in the hemagglutination inhibition test or ELISA or by
observing the presence of IgM antibody in a single acute-
phase serum sample. PCR assay can also be used.
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In a pregnant woman exposed to rubella virus, the pres-
ence of IgM antibody indicates recent infection, whereas
a 1:8 or greater titer of IgG antibody indicates immunity
has occurred, an amniocentesis can reveal whether there is
rubella virus in the amniotic fluid, which indicates definite
fetal infection.

Treatment

There is no antiviral therapy.
Prevention
Prevention involves immunization with the live, attenu-
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ated vaccine. The vaccine is effective and long-lasting (at
FIGURE 39–5
Rubella—note fine, almost confluent macular-
least 10 years) and causes few side effects, except for tran-
papular rash. (Used with permission from Stephen E. Gellis, MD.)
sient arthralgias in some women. It is given subcutaneously
with measles and mumps vaccine) and to unimmunized
3 days. When rubella occurs in adults, especially women,
young adult women if they are not pregnant and will use
polyarthritis caused by immune complexes often occurs.
contraception for the next 3 months. There is no evidence
that the vaccine virus causes malformations. Because it is a
Congenital Rubella Syndrome
live vaccine, it should not be given to immunocompro-
The significance of rubella virus is not as a cause of mild
childhood disease but as a teratogen. When a nonimmune
The vaccine has caused a significant reduction in the
pregnant woman is infected during the first trimester,
incidence of both rubella and congenital rubella syndrome.
especially the first month, significant congenital malforma-
It induces some respiratory IgA, thereby interrupting the
tions can occur as a result of maternal viremia and fetal mised patients or to pregnant women.
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spread of virulent virus by nasal carriage.
infection. The increased rate of abnormalities during the
Immune serum globulins (IG) can be given to pregnant
early weeks of pregnancy is attributed to the very sensitive
women in the first trimester who have been exposed to a
organ development that occurs at that time. The malforma-
tions are widespread and involve primarily the heart (e.g.,
pregnancy is not an option. The main problems with giving
patent ductus arteriosus), the eyes (e.g., cataracts), and the
IG are that there are instances in which it fails to prevent
brain (e.g., deafness and mental retardation).
fetal infection and that it may confuse the interpretation of
In addition, some children infected in utero can con-
serologic tests. If termination of the pregnancy is an option,
tinue to excrete rubella virus for months after birth, which
it is recommended to attempt to determine whether the
is a significant public health hazard because the virus can
be transmitted to pregnant women. Some congenital shed-
preceding “Laboratory Diagnosis” section.
ders are asymptomatic and without malformations and
To protect pregnant women from exposure to rubella
hence can be diagnosed only if the virus is isolated. Con-
virus, many hospitals require their personnel to demon-
genitally infected infants also have significant IgM titers mother and fetus have been infected as described in the
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strate immunity, either by serologic testing or by proof of
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and persistent IgG titers long after maternal antibody has
immunization.
disappeared.
Laboratory Diagnosis
Rubella virus can be grown in cell culture, but it produces
Several other medically important togaviruses are described
little cytopathic effect (CPE). It is therefore usually
in the chapter on arboviruses (see Chapter 42).
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