THE DEADLY SARS VIRUS (SARS-LTKE
CORONAVIRUSES OR SARS-COV)
CORONAVIRUSES OR SARS-COV)
In November 2002, there was an outbreak of severe atyp-
ical pneumonias in China. The cause of this outbreak was
not known, and was initially confined to the mainland. In
early 2003, this disease had spread to Hong Kong, Singa-
pore, and Toronto, Canada, and the syndrome was called
SARS (Severe Acute Respiratory Syndrome).
Within a few weeks of the description of this syndrome,
it was discovered that SARS is caused by a virus, specif-
ically a novel coronavirus' (SARS-CoV). Coronaviruses
are a family of enveloped, positive (+) single stranded
RNA viruses, previously only known to cause the com-
mon cold in humans. Before the outbreak was controlled,
it had spread to 29 countries and territories, and infected
over 8000 people.
SARS is an example of an emerging infectious dis-
ease. This virus was not known to exist previously,
and since the initial outbreak has not caused any
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additional natural outbreaks. An identical virus has
not been found to exist in any natural reservoir,
though similar viruses have been found in bats.
SARS-like coronaviruses have been isolated from
Himalayan palm civets and from raccoon dogs in
markets in China. How people were first infected with
this virus remains unclear but one theory is that it
was a mutated virus of animals that crossed the
species barrier and caused the epidemic.
Clinical Features of SARS
The primary mode of transmission is thought to occur
via direct or indirect contact of mucous membrane (eyes,
nose, or mouth) with infectious respiratory droplets.
While this virus is not as transmissible as was previ-
ously thought, it appears that there were a few persons
who were responsible for more transmissions, this is
called super-spreading events. A lot of the transmis-
sion of this virus from one person to the next, occurred
in hospitals and other health care settings. After a 2-49
day incubation period, people infected with BARS often
presented with fevers, myalgias, and chills, and later
developed a dry cough, chest pain (pleurisy) and short-
ness of breath (dyspnea). Surprisingly, few patients de-
velop sore throat or rhinorrhea as one might expect from
a coronavirus. Most patients present to the doctor with
an abnormal chest radiograph or chest CT scan showing
alveolar consolidation, which can progress to frank
ARDS (the acute respiratory distress syndrome). About
20 to 30 percent of patients required admission to an in-
tensive care unit, and most of them required mechanical
ventilation. About 8% of people with SARS died, and
this was primarily due to respiratory failure.
Diagnosis
During the outbreak, a ease definition was developed by
the World Health Organization (WHO), which had a high
sensitivity but a very low specificity. This is because the
clinical features are not unique to this virus or disease.
More accurate diagnoses can be made by Reverse-
Tra.nscriptase (quantitative)-Polymerase Chain Reaction
(PCR) testing for the viral RNA in respiratory secretions,
feces, urine and from lung biopsy tissue, or seroconver-
sion (detection of antibodies in the blood to the virus).
Treatment
The optimal therapy of SARS is not known. Patients
with suspected SARS are generally treated empirically
with broad-spectrum antibacterial drugs that are effec-
tive against other agents that cause community
acquired pneumonia. Ribavirin was often used in the
treatment of SARS, but it was later shown in animal
models that this drug had no effect against this virus.
Corticosteroids were also used frequently, though there
is no solid clinical or animal data to support their use.
Generally treatment is supportive with mechanical ven-
tilation and intensive care. --------