Page 348 - Review of Medical Microbiology and Immunology ( PDFDrive )

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CHAPTER 40 RNA Nonenveloped Viruses
disease is characterized by a vesicular rash on the hands
Serologic tests are of little value, because there are a large
and feet and ulcerations in the mouth, mainly in children.
number of serotypes and no common antigen. There is no
Group B–Specific Diseases
antiviral therapy or vaccine available.
Pleurodynia (Bornholm disease, epidemic myalgia, “devil’s
grip”) is characterized by fever and severe pleuritic-type
chest pain. Note that pleurodynia is pain due to an infec-
In view of the difficulty in classifying many enteroviruses,
tion of the intercostal muscles (myositis), not of the pleura.
all new isolates have been given a simple numerical desig-
Myocarditis and pericarditis are characterized by fever, 4. Other Enteroviruses
chest pain, and signs of congestive failure. Dilated cardio-
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nation since 1969.
myopathy with global hypokinesia of the myocardium is a
Enterovirus 68 (EV68 and EVD68) is a common cause
of respiratory tract disease that ranges from a mild com-
feared sequela that often requires cardiac transplantation to
sustain life. Diabetes in mice can be caused by pancreatic
implicated as a cause of acute flaccid paralysis (“poliolike”)
damage as a result of infection with Coxsackie virus B4.
in children. A PCR test is available. There is no antiviral
This virus is suspected to have a similar role in juvenile
diabetes in humans.
therapy and no vaccine.
Enterovirus 70 is the main cause of acute hemorrhagic
Diseases Caused by Both Groups
conjunctivitis, characterized by petechial hemorrhages on
Both groups of viruses can cause aseptic meningitis, mild
paresis, and acute flaccid paralysis similar to poliomyelitis.
and there is no therapy.
Enterovirus 71 is one of the leading causes of viral cen-
Upper respiratory infections, pharyngitis, and minor febrile
tral nervous system disease, including meningitis, encepha-
illnesses with or without rash can occur also. the bulbar conjunctivas. Complete recovery usually occurs,
litis, and paralysis. It also causes diarrhea, pulmonary
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hemorrhages, hand-foot-and-mouth disease, and herpan-
Laboratory Diagnosis
gina. Enterovirus 72 is hepatitis A virus, which is described
The diagnosis is made either by isolating the virus in cell
culture or suckling mice or by observing a rise in titer of
neutralizing antibodies. A rapid (2.5-hour) polymerase
chain reaction (PCR)–based test for enteroviral RNA in the
RHINOVIRUSES
spinal fluid is useful for making a prompt diagnosis of viral
Disease
meningitis because culture techniques typically take days to
obtain a result.
These viruses are the main cause of the common cold.
Treatment & Prevention
Important Properties
There is neither antiviral drug therapy nor a vaccine avail-
There are more than 100 serologic types, which explains
able against these viruses. No passive immunization is
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recommended.
Table 40–1, they replicate better at 33°C than at 37°C,
which explains why they affect primarily the nose and con-
3. Echoviruses
junctiva rather than the lower respiratory tract. Because
they are acid-labile, they are killed by gastric acid when
The prefix ECHO is an acronym for enteric cytopathic
swallowed. This explains why they do not infect the gastro-
human orphan. Although called “orphans” because they
intestinal tract, unlike the enteroviruses. The host range is
were not initially associated with any disease, they are now
limited to humans and chimpanzees.
known to cause a variety of diseases such as aseptic menin-
gitis, upper respiratory tract infection, febrile illness with
and without rash, infantile diarrhea, and hemorrhagic
conjunctivitis.
Replication is similar to that of poliovirus. The cell surface
The structure of echoviruses is similar to that of other
receptor for rhinoviruses is intracellular adhesion molecule
enteroviruses. More than 30 serotypes have been isolated. Summary of Replicative Cycle
1 (ICAM-1), an adhesion protein located on the surface of
In contrast to Coxsackie viruses, they are not pathogenic
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many types of cells.
for mice. Unlike polioviruses, they do not cause disease in
monkeys. They are transmitted by the fecal–oral route and
occur worldwide. Pathogenesis is similar to that of the
other enteroviruses.
There are two modes of transmission for these viruses. In
Along with Coxsackie viruses, echoviruses are one of
the past, it was accepted that they were transmitted directly
the leading causes of aseptic (viral) meningitis. The
from person to person via aerosols of respiratory droplets.
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