Severe Acute Respiratory Syndrome (SARS)

Carly A Page, University of Maryland, Baltimore, MD, USA
Matthew B Frieman, University of Maryland, Baltimore, MD, USA

Published online: June 2011

DOI: 10.1002/9780470015902.a0004025.pub2

Severe acute respiratory syndrome (SARS) is a disease that caused significant morbidity and mortality during the outbreak in 2002–2003. In early 2003, a novel coronavirus was identified as the aetiological agent of SARS and is currently known as SARS-CoV. This virus has since been extensively characterised and studied as a model for acute respiratory infection. SARS-CoV utilises a number of virally encoded proteins to subvert the host immune system and establish infection. The ensuing immune dysregulation often results in prolonged, severe disease and sometimes death that does not always associate with the long-term presence of virus. In addition to being an important respiratory virus model, SARS-CoV is also an important model for emerging infectious diseases as it emerged from natural animal reservoirs. Here we review the epidemiology, clinical disease and virology of this disease-causing virus.

Key Concepts:

  • Emerging viruses are able to jump from animals to people and cause infections.
  • Epidemiological controls can slow down respiratory virus epidemics.
  • Understanding viral pathogenesis aids in our ability to fight current and future virus outbreaks.

Keywords: SARS-CoV; coronavirus; emerging disease; zoonotic disease; respiratory infection

Figure 1. Superspread events. In this schematic, based on the SARS epidemic course in Singapore, individuals who directly spread SARS-CoV to more than five individuals are marked with red squares. Spread from these individuals accounted for the majority of the disease propagation. The star marks the initial infection. Individuals who spread the disease but to three or fewer other people are marked in blue. Note that in one case, transmission from one super spreading individual to another occurred through a nonsuperspreading intermediary; this person is noted in green. Adapted from CDC (USA) Morbidity and Mortality Weekly Report (9 May 2003).
Figure 2. Comparison of the SARS-CoV gene organisation to those of other coronaviruses. Based on antigenic reactivity, coronaviruses were classified into three groups. A representative member of each group is shown. The SARS-CoV genome contains 14 ORFs, and is most similar to group 2 coronaviruses. TGEV – transmissible gastroenteritis virus; MHV – mouse hepatitis virus; and IBV – infectious bronchitis virus. The haemagglutinin-esterase (HE) protein is present in some group 2 coronaviruses.
Figure 3. Structure of SARS-CoV ORF1. ORF1 accounts for approximately two-thirds of the genome and encodes for 16 proteins, all produced as 1 polyprotein. Translation of ORF1b is initiated by a –1 ribosomal frameshift at the location noted by the grey arrow. The functions of seven of the nonstructural proteins encoded by ORF1a and ORF1b are known or predicted by sequence homology. Abbreviations: ADRP, ADP-ribose 12-phosphatase; PL2pro, papain-like protease; 3CLpro, main protease; ssRBP, ssRNA binding protein; RNApol, RNA-dependent RNA polymerase; ExoN, exoribonuclease; NendoU, endoribonuclease; and 2¢-OMT, 2¢-O-ribose methyltransferase.
Figure 4. SARS-CoV subgenomic RNAs. The coronavirus polymerase complex mediates the synthesis of eight subgenomic mRNAs, with only the 5¢ ORF of each RNA translated into protein. Each subgenomic RNA contains a common leader sequence, derived from the 5¢ end of genomic RNA. The leader is most likely joined to the body of each subgenomic RNA during synthesis of negative-strand RNA. In this process, the RNA polymerase ‘skips’ from the transcription-regulating sequence (TRS) (denoted by brown boxes) to the 5¢ leader sequence, in blue. Subsequently, subgenomic mRNAs are synthesised from these subgenomic negative sense RNAs. This process is shown for mRNA2.
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 Further Reading
    Frieman M and Baric R (2008) Mechanisms of severe acute respiratory syndrome pathogenesis and innate immunomodulation. Microbiology and Molecular Biology Reviews 72(4): 672–685, Table of Contents. Review. PubMed PMID: 19052324; PubMed Central PMCID: PMC2593566.
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Related Sub-Topics:

Virus Diseases | Viruses Infecting Humans | RNA Viruses
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Article Title: Severe Acute Respiratory Syndrome (SARS)
 
How to Cite close
Page, Carly A, and Frieman, Matthew B(Jun 2011) Severe Acute Respiratory Syndrome (SARS). In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0004025.pub2]