Severe Acute Respiratory Syndrome

Aka: Severe Acute Respiratory Syndrome, SARS, SARS-CoV, SARS Coronavirus

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II. Epidemiology

  1. Asia has been epicenter of SARS outbreaks
  2. First described as an Atypical Pneumonia in November 2002, Mainland China
    1. Later, in 2003 had spread to Hong Kong, Singapore and Toronto, Canada
    2. Ultimately, infected 8000 people in 29 countries
    3. Source may have been at open markets from bats, himalayan civets or raccoon dogs

III. Pathophysiology

  1. SARS-CoV is a novel Coronavirus spread by respiratory droplet transmission
  2. Coronaviruses are in the family Coronaviridae
    1. Coronaviridae are a family of enveloped RNA Viruses with a helical capsid
    2. Coronaviridae are Message Sense RNA Viruses (Positive Stranded, +ssRNA)
      1. Message sense RNA (+ssRNA) are identical to Messenger RNA (mRNA)
      2. Like mRNA, +ssRNA may be immediately translated by host ribosomes into Protein
  3. Infectivity
    1. Mucous membrane contact with infectious respiratory droplets

IV. Symptoms

  1. Background
    1. Distinctly different than typical Coronavirus presentations
    2. Pharyngitis and Rhinorrhea are absent in SARS (contrast with typical coronavirus Common Cold)
  2. Fever (Temperature over 100.4 F or 38 C)
  3. Chills
  4. Myalgias
  5. Non-productive Cough
  6. Pleuritic Chest Pain
  7. Shortness of Breath
  8. Headache
  9. Dizziness

V. Imaging

  1. Chest XRay (abnormal in 75% of cases at presentation)
    1. Patchy consolidation in peripheral lung fields
  2. Chest CT
    1. Peripheral "ground-glass" opacifications

VI. Labs

  1. SARS Viral RNA PCR
  2. Complete Blood Count with Platelets
    1. Lymphocyte Count >4000/uL or <1500/uL
    2. Neutrophil Count <2000/uL
    3. Platelet Count <150,000/mm3

VII. Management

  1. Cover differential diagnosis
    1. Empiric treatment for Bacterial Pneumonia
  2. Non-specific measures used in SARS cases
    1. Indications
      1. Fever >48 hours
      2. Thrombocytopenia
      3. Leukopenia
    2. Medications
      1. See Covid19
      2. Methylprednisolone
      3. Ribavirin was orginally used, but later found ineffective

VIII. Course

  1. Incubation Period: 2-16 days (mean 5-6 days)
  2. ICU admission rate: 23-30%
  3. Mechanical Ventilation required: 13.8%
  4. Mortality: 3.6% (up to 8%)
    1. Associated with major comorbidities
  5. Time at which further hospital transmission unlikely
    1. Twenty days from last known SARS case onset

IX. Prevention

  1. Respiratory protection
    1. N95 or equivalent mask
  2. SARS Vaccine
    1. WHO trials of Vaccine due to start winter of 2004

X. Risk Factors

  1. Close contact to infected patients
    1. Household contacts
    2. Healthcare workers
  2. Highest risk transmission to unmasked healthcare worker
    1. BiPap or CPAP administration
    2. Nebulizer administration
    3. Intubation
    4. Bronchoscopy

XI. Prognosis: Predictors of worse prognosis

  1. Advanced age
  2. Lactate Dehydrogenase (LDH) increased
  3. Neutrophilia

XII. References

  1. Lee (2003) N Engl J Med 348:1986-94 [PubMed]
  2. Varia (2003) CMAJ 169(4):285-92 [PubMed]

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