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Preface

Summary

1. Timeline

2. Virology

3. Transmission

4. Epidemiology

5. Prevention

6. Case Definition

7. Diagnostic Tests

8. Clinical Presentation and Diagnosis

9. SARS Treatment

10. Pediatric SARS



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6. Case Definition

WHO Case Definition

As defined by the World Health Organization (WHO), a suspected case is classified as being disease in a person with a documented fever (temperature >38 C), lower respiratory tract symptoms, and contact with a person believed to have had SARS or a history of travel to a geographic area where there has been documented transmission of the illness.

A suspected case with 1) chest radiographic findings of pneumonia, 2) acute respiratory distress syndrome, or 3) an unexplained respiratory illness resulting in death with autopsy findings consistent with the pathology of ARDS without an identifiable cause is considered a probable case.

The WHO Case Definition is available at: http://www.who.int/csr/sars/casedefinition/en/.

Clinicians are advised that patients should not have their case definition category downgraded while still awaiting results of laboratory testing or on the basis of negative results. See Use of laboratory methods for SARS diagnosis.

Suspect case

1. A person presenting after 1 November 20021 with history of:

  • high fever (>38 C)

AND

  • cough or breathing difficulty

AND one or more of the following exposures during the 10 days prior to onset of symptoms:

2. A person with an unexplained acute respiratory illness resulting in death after 1 November 20021, but on whom no autopsy has been performed

AND one or more of the following exposures during to 10 days prior to onset of symptoms:

1 The surveillance period begins on 1 November 2002 to capture cases of atypical pneumonia in China now recognized as SARS. International transmission of SARS was first reported in March 2003 for cases with onset in February 2003.

2 Close contact: having cared for, lived with, or had direct contact with respiratory secretions or body fluids of a suspect or probable case of SARS.

Probable case

1. A suspect case with radiographic evidence of infiltrates consistent with pneumonia or respiratory distress syndrome (RDS) on chest X-ray (CXR).

2. A suspect case of SARS that is positive for SARS coronavirus by one or more assays. See Use of laboratory methods for SARS diagnosis.

3. A suspect case with autopsy findings consistent with the pathology of RDS without an identifiable cause.

Exclusion criteria

A case should be excluded if an alternative diagnosis can fully explain their illness.

Reclassification of cases

As SARS is currently a diagnosis of exclusion, the status of a reported case may change over time. A patient should always be managed as clinically appropriate, regardless of their case status.

  • A case initially classified as suspect or probable, for whom an alternative diagnosis can fully explain the illness, should be discarded after carefully considering the possibility of co-infection.
  • A suspect case who, after investigation, fulfils the probable case definition should be reclassified as "probable".
  • A suspect case with a normal CXR should be treated, as deemed appropriate, and monitored for 7 days. Those cases in whom recovery is inadequate should be re-evaluated by CXR.
  • Those suspect cases in whom recovery is adequate but whose illness cannot be fully explained by an alternative diagnosis should remain as "suspect".
  • A suspect case who dies, on whom no autopsy is conducted, should remain classified as "suspect". However, if this case is identified as being part of a chain transmission of SARS, the case should be reclassified as "probable".
  • If an autopsy is conducted and no pathological evidence of RDS is found, the case should be "discarded".

CDC Case Definition

The Centers for Disease Control and Prevention have added laboratory criteria for evidence of infection with the SARS-associated coronavirus (SARS-CoV) to the interim surveillance case definition.

Using the new laboratory criteria, a SARS case is laboratory-confirmed if one of the following is met:

  • detection of the SARS-CoV antibody by indirect fluorescent antibody (IFA) or enzyme-linked immunosorbent assay (ELISA)
  • isolation of SARS-CoV in tissue culture
  • detection of SARS-CoV RNA by reverse transcriptase- polymerase chain reaction (RT-PCR), which must be confirmed by a second PCR test

Negative laboratory results for PCR, viral culture, or antibody tests obtained within 21 days of illness do not rule out coronavirus infection. In these cases, an antibody test of a specimen obtained more than 21 days after the onset of illness is needed to determine infection.

The "Updated Interim Surveillance Case Definition for Severe Acute Respiratory Syndrome (SARS)", published April 29, 2003, is available on the Internet at

http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5217a5.htm


 

 
 
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