Page 331 - Review of Medical Microbiology and Immunology ( PDFDrive )

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PART IV Clinical Virology
320
Measles in a pregnant woman leads to an increased risk
of stillbirth rather than congenital abnormalities. Measles
activities and the other with cell-fusing and hemolytic
activities (see Table 39–4).
virus infection of the fetus is more severe than rubella virus
The virus has a single serotype. Neutralizing antibody is
infection, so the former typically causes fetal death, whereas
directed against the hemagglutinin. The internal nucleo-
the latter causes congenital abnormalities.
Atypical measles occurs in some people who were given
test used for diagnosis. Humans are the natural host.
the killed vaccine and were subsequently infected with
measles virus. It is characterized by an atypical rash without
Summary of Replicative Cycle
Koplik’s spots. Because the killed vaccine has not been used capsid protein is the S (soluble) antigen detected in the CF
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for many years, atypical measles occurs only in adults and
Replication is similar to that of measles virus (see page 318).
is infrequent.
Transmission & Epidemiology
Laboratory Diagnosis
Most diagnoses are made on clinical grounds, but the virus
Mumps occurs worldwide, with a peak incidence in the
can be isolated in cell culture. A greater than fourfold rise
winter. About 30% of children have a subclinical (inappar-
in antibody titer can be used to diagnose difficult cases.
ent) infection, which confers immunity. There were only
PCR assay is also used.
683 reported cases of mumps in the United States in
1997—a finding attributed to the widespread use of the
Treatment
vaccine. However, in 2006, a resurgence of mumps
occurred, with 6584 cases being recorded despite a high
There is no antiviral therapy available.
(87%) coverage rate for the vaccine.
Prevention
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Prevention rests on immunization with the live, attenuated
The virus infects the upper respiratory tract and then
vaccine. The vaccine is effective and causes few side effects.
spreads through the blood to infect the salivary glands,
It is given subcutaneously to children at 15 months of age,
especially the parotid gland, testes, ovaries, pancreas, and,
usually in combination with rubella and mumps vaccines.
in some cases, meninges. Alternatively, the virus may
The vaccine should not be given to children prior to 15
ascend from the buccal mucosa up Stensen’s duct to the
months of age, because maternal antibody in the child
parotid gland.
can neutralize the virus and reduce the immune response.
Lifelong immunity occurs in persons who have had the
Because immunity can wane, a booster dose is recom-
disease. There is a popular misconception that unilateral
mended. The vaccine contains live virus, so it should not be
given to immunocompromised persons or pregnant
Mumps occurs only once; subsequent cases of parotitis can
women. The vaccine has decreased the number of cases of
be caused by other viruses such as parainfluenza viruses, by
measles greatly in the United States; there were only 138 mumps can be followed by mumps on the other side.
bacteria, and by duct stones. Maternal antibody passes the
reported cases of measles in 1997. However, outbreaks still
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placenta and provides protection during the first 6 months
occur among unimmunized individuals (e.g., children in
of life.
inner cities and in developing countries).
The killed vaccine should not be used. Immune globu-
lin can be used to modify the disease if given to unimmu-
nized individuals early in the incubation period. This is
After an incubation period of 18 to 21 days, a prodromal
especially necessary if the unimmunized individuals are
stage of fever, malaise, and anorexia is followed by tender
immunocompromised.
swelling of the salivary glands, either unilateral or bilateral
(Figure 39–4). There is a characteristic increase in parotid
gland pain when drinking citrus juices. The disease is typi-
MUMPS VIRUS
Disease
Two complications are of significance. One is orchitis in
postpubertal males, which, if bilateral, can result in sterility.
This virus causes mumps, a disease characterized by salivary cally benign and resolves spontaneously within 1 week.
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Postpubertal males have a fibrous tunica albuginea, which
gland swelling. It occurs primarily in childhood. (See “Clini-
resists expansion, thereby causing pressure necrosis of the
cal Findings” section for a more complete description.)
spermatocytes. Unilateral orchitis, although quite painful,
Important Properties
gitis, which is usually benign, self-limited, and without
The genome RNA and nucleocapsid are those of a typical
sequelae. Mumps virus, Coxsackie virus, and echovirus are
the three most frequent causes of viral (aseptic) meningitis.
paramyxovirus. The virion has two types of envelope
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