Severe Acute Respiratory Syndrome

Clinical information

Symptoms

Initial symptoms are flu-like and may include: fever, myalgia, lethargy, gastrointestinal symptoms, cough, sore throat and other non-specific symptoms. The only symptom that is common to all patients appears to be a fever above 38 °C (100.4 °F). Shortness of breath may occur later.

Related Topics:
Fever - Myalgia - Lethargy - Gastrointestinal symptoms - Cough - Sore throat - °C - °F - Shortness of breath

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Symptoms usually appear 2–10 days following exposure, but up to 13 days has been reported. In most cases symptoms appear within 2–3 days. About 10–20% of cases require mechanical ventilation.

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Physical signs

Early physical signs are inconclusive and may be absent. Some patients will have tachypnea and crackles on auscultation. Later, tachypnea and lethargy become more prominent.

Related Topics:
Tachypnea - Crackles - Auscultation - Lethargy

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Investigations

The Chest X-ray (CXR) appearance of SARS is variable. There is no pathognomonic appearance of SARS but is commonly felt to be abnormal with patchy infiltrates in any part of the lungs. The initial CXR may be clear.

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White blood cell and platelet counts are often low. Early reports indicated a tendency to relative neutrophilia and a relative lymphopenia — relative because the total white count itself tends to be low. Other suggestive laboratory tests are raised lactate dehydrogenase and slightly raised creatinine kinase and C-Reactive protein levels.

Related Topics:
White blood cell - Platelet - Neutrophilia - Lymphopenia - Total white count - Lactate dehydrogenase - Creatinine kinase - C-Reactive protein

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Diagnostic tests

With the identification and sequencing of the DNA of the coronavirus supposedly responsible for SARS on April 12, 2003, several diagnostic test kits have been produced and are now being tested for their suitability for use.

Related Topics:
Coronavirus - April 12 - 2003

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Three possible diagnostic tests have emerged, each with drawbacks. The first, an ELISA (enzyme-linked immunosorbent assay) test detects antibodies to SARS reliably but only 21 days after the onset of symptoms. The second, an immunofluorescence assay, can detect antibodies 10 days after the onset of the disease but is a labour and time intensive test, requiring an immunofluorescence microscope and an experienced operator. The last test is a PCR (polymerase chain reaction) test that can detect genetic material of the SARS virus in specimens ranging from blood, sputum, tissue samples and stool. The PCR tests so far have proven to be very specific but not very sensitive. This means that while a positive PCR test result is strongly indicative that the patient is infected with SARS, a negative test result does not mean that the patient does not have SARS.

Related Topics:
ELISA - Immunofluorescence - Immunofluorescence microscope - PCR - Polymerase chain reaction - Blood - Sputum - Tissue sample - Stool - Specific - Sensitive

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The WHO has issued guidelines for using these diagnostic tests http://www.who.int/csr/sars/labmethods/en/.

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There is currently no rapid screening test for SARS and research is ongoing.

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Diagnosis

SARS may be suspected in a patient who has:

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• any of the symptoms including a fever of 38 degrees Celsius (100.4 degrees Fahrenheit) or more AND
• either a history of
• contact with someone with a diagnosis of SARS within the last 10 days OR
• travel to any of the regions identified by the WHO as areas with recent local transmission of SARS (affected regions as of 10 May 2003 http://www.who.int/csr/sarsareas/2003_05_10/en/ were parts of China, Hong Kong, Singapore and the province of Ontario, Canada).

A probable case of SARS has the above findings plus positive chest x-ray findings of atypical pneumonia or respiratory distress syndrome.

Related Topics:
Atypical pneumonia - Respiratory distress syndrome

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With the advent of diagnostic tests for the coronavirus probably responsible for SARS, the WHO has added the category of "laboratory confirmed SARS" for patients who would otherwise fit the above "probable" category who do not (yet) have the chest x-ray changes but do have positive laboratory diagnosis of SARS based on one of the approved tests (ELISA, immunofluorescence or PCR).

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Mortality rate

The mortality rate varies across countries and reporting organizations. In early May, for consistency with similar metrics of other diseases, the World Health Organization (WHO) and US Centers for Disease Control and Prevention was quoting 7%, or the number of deaths divided by probable cases, as the SARS mortality rate. Others spoke in favour of a 15% figure, derived from number of death divided by the number who recovered or died, saying it reflects the real situation more accurately. As the outbreak progressed both mortality measures approached 10%.

Related Topics:
World Health Organization - Centers for Disease Control and Prevention

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One reason for the difficulties in plotting a reliable mortality figure is that the number of infections and the number of deaths are increasing at completely different rates. A possible explanation involves a secondary infection as a causal agent in the disease (See Eric Lerner's analysis), but whatever the cause, the mortality numbers are bound to change.

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Mortality by age group as of 8 May 2003 is below 1% for people aged 24 or younger, 6% for those 25 to 44, 15% in those 45 to 64 and more than 50% for those over 65. http://www.who.int/csr/sarsarchive/2003_05_07a/en/

Related Topics:
8 May - 2003

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For comparison, the case fatality rate for influenza is usually about 0.6% (primarily among the elderly) but can rise as high as 33% in locally severe epidemics of new strains. The mortality rate of the primary viral pneumonia form is about 70%.

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Treatment

Antibiotics have not proven to be effective. Treatment of SARS so far has been largely supportive with anti-pyretics, supplemental oxygen and ventilatory support as needed.

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Suspected cases of SARS must be isolated, preferably in negative pressure rooms, with full barrier nursing precautions taken for any necessary contact with these patients.

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There was initially anecdotal support for steroids and the antiviral drug ribavirin, but no published evidence has supported this therapy. Many clinicians now suspect that ribavirin is detrimental.

Related Topics:
Steroid - Antiviral drug - Ribavirin

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Researchers are currently testing all known antiviral treatments for other diseases including AIDS, hepatitis, influenza and others on the SARS-causing coronavirus.

Related Topics:
AIDS - Hepatitis - Influenza

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There may be some benefit from using steroids and other immune system modulating agents in the treatment of the more acute SARS patients as there is some evidence that part of the more serious damage SARS causes is also due to the body's own immune system overreacting to the virus. Research is continuing in this area.

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In December 2004 it was reported that Chinese researchers had produced a SARS vaccine. It has been tested on a group of 36 volunteers, 24 of whom developed antibodies against the virus.

Related Topics:
December 2004 - Vaccine

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