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Causative Agent

SARS-associated coronavirus (SARS-CoV)

Incubation Period

Typically 2-7 days but may be prolonged up to 10-14 days

Infectious Period

Throughout the symptomatic phase of the disease.

Although there may be persistent viral shedding in the stool for up to 6 weeks after recovery from clinical illness, transmission of the disease has not been documented from asymptomatic nor convalescent individuals.


Respiratory droplets and less often by direct contact with objects contaminated by respiratory secretions. Oral-faecal and airborne transmission may occur under special circumstances.


The first outbreak of this new infectious disease occurred in Guangdong, China in November 2002, but soon spread to several Asian countries and Canada by March 2003. The outbreak ended on 5th July 2003, although two cases attributed to laboratory transmission were reported from Singapore and Taiwan in September and December 2003, respectively. Another laboratory associated outbreak occurred in China in April 2004.

The majority of transmission occurred in hospitals and other institutional healthcare settings.

By the end of the worldwide outbreak in July 2003, a total of 8096 cases were reported, with 774 deaths and a case-fatality rate of 9.6 percent.

Between March and May 2003, a total of 238 cases, with 33 deaths, were reported  in Singapore. 41% of the cases were healthcare workers, and 68% were females. The median age of all SARS cases was 36 (range 4 to 90) years.

  • The clinical presentation is non-specific and resembles other influenza-like illnesses.
  • The prodrome is prolonged lasting from 3 to 7 days and  is characterised  by  fever, malaise, headache and myalgia. Respiratory symptoms and diarrhoea, if present, typically occur a few days after the onset of fever.
  • Physical examination is not helpful except as a gauge of severity of illness.
  • Clinical manifestations vary from mild infection (80%) to severe disease (20%) with respiratory failure and death.
  • Death is usually caused by combination of respiratory and multiorgan failure.
  • The clinical course is marked by deterioration in the second week of illness and recovery by the third week in the majority of cases. Children have a shorter and milder course of illness.
  • There is no evidence at present of intra-partum infection.

  • Chest X-ray. This may be normal early in the course of the disease. However, the more distinct radiographic features include:
    • a predominantly peripheral location of air-space opacity;
    • progression from unifocal to multifocal or bilateral lung involvement during treatment; and
    • lack of cavitation, lymphadenopathy and pleural effusion.

  • At the time of and in the immediate aftermath of the SARS epidemic, both the World Health Organization (WHO) and the US CDC issued case definitions for SARS.
  • According to the WHO, a case of SARS is notifiable if it occurs in an individual with laboratory confirmation of infection who either meets the clinical case definition or has worked in a laboratory with live SARS coronavirus or with clinical specimens infected with SARS coronavirus.
  • The clinical case definition used by the WHO includes:
    • A history of fever or documented fever; and
    • One or more symptoms of lower respiratory tract illness (cough, difficulty in breathing, shortness of breath); and
    • Radiographic evidence of lung infiltrates consistent with pneumonia or acute respiratory distress syndrome (ARDS) or autopsy findings consistent with the pathology of pneumonia or ARDS without an identifiable cause; and
    • No alternative diagnosis fully explaining the illness.
  • Laboratory diagnostic tests that are required include one or both of the following:
  • Detection of virus (reverse transcriptase PCR) assay detecting viral RNA present in two separate samples, or virus culture from any clinical specimen. These two samples can be obtained from either two separate sites (e.g. nasopharyngeal and stool) or from the same site, but at different times (e.g. sequential nasopharyngeal aspirates); and/or
  • Detection of antibody (a rise in antibody titre, either from negative to positive or at least a four-fold increase) by enzyme-linked immunosorbent assay (ELISA) and/or immunofluorescent assay (IFA).
  • These are highly sensitive and specific but positive only from the second week of illness onwards.

A legally notifiable disease in Singapore. Notify Ministry of Health (Form MD 131 or electronically via CD-LENS) not later than 24 hours from the time of diagnosis. Notify MOH immediately on suspicion. Call MOH Communicable Diseases Surveillance team at: 98171463

  • All suspected and probable/confirmed cases of SARS will be isolated and treated at the Communicable Disease Centre (CDC).
  • Symptomatic and supportive treatment for all cases.
  • Ribavirin which was used initially during the pandemic has been shown to be ineffective in vitro towards SARS coronavirus and is associated with significant toxicities.
  • Some centres recommend a short course of moderate to high dose corticosteroids.
  • There may be a role for treatment using protease inhibitor like lopinavir, immunoglobulins and interferon based on prior experience.

  • Patients with SARS should ideally be nursed in negative pressure isolation rooms.
  • Respiratory (droplet and airborne) and contact precautions are required.
  • Procedures which may aerosolize the virus (viz. nebulizer therapy) should be avoided if possible.
  • Movement of patients (viz. for scans or other procedures) within the hospital should be kept to a minimum.

  • Public health measures to limit transmission include:
    • Shortening the time from symptom-onset to isolation of patients (viz. early case detection)
    • Effective contact tracingQuarantine of exposed persons
  • Surveillance of fever clusters and atypical pneumonia cases
  • A combination of clinical and relevant epidemiological features should raise suspicions of SARS. However, it is quite likely that a de novo case will be missed initially, and success of current preventive policies will be gauged by the size of the consequent outbreak.
  • Efforts are underway to prepare a vaccine but are still at an early stage.


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  2. CDC (Atlanta) Accessed Aug 2010
  3. WHO Accessed Aug 2010
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  6. Gopalakrishna G, Choo P, Leo YS et al. SARS transmission and hospital containment. Emerg Infect Dis. 2004; 10:395-400
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  8. Case definitions for the 4 diseases requiring notification to WHO in all circumstances under the IHR (2005). Wkly Epidemiol Rec 2009; 84:52
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  10. Stockman L.J., Bellamy R., Garner P. SARS: systematic review of treatment effects. PLoS Med 3. e343.2006
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