February 2003, Asia reported an outbreak of severe acute respiratory syndrome, commonly known as SARS. SARS is a viral respiratory illness caused by the virus SARS-associated coronavirus (SARS-CoV). Within a few months the virus spread to over two dozen countries, causing SARS to be considered a global infection. The virus spread to North America, Europe, South America and Asia before it was contained in 2003. A total of 8,098 people were infected by SARS worldwide during the 2003 outbreak. The viral infection claimed 774 lives. [1]
Morphology of SARS:
SARS is part of the Coronavirus family. Coronavirus is a family of 15 species of viruses with similar characteristics. Coronavirus particles are irregular in shape and are 60-220nm in diameter. The SARS species is 100nm is diameter. The coronavirus particles have an outer envelope with distinctive ‘club shaped’ peplomers. The envelope give the virus a ‘crown’ appearance from which the name was derived from as Latin for crown is corona. The envelope contains three proteins and in shown there is a fourth present:
· Spike protein: receptor binding, cell fusion, major antigen
· Envelope protein: small, envelope-associated protein
· Membrane protein: transmembrane - budding & envelope formation
· Haemagglutinin-esterase (Only present in some coronaviruses)
Cornaviruses contains the longest single stranded, non-segmented strand of RNA in all RNA viruses. The genome has a 5 ' methylated cap and 3 ' poly-A tail and functions directly as mRNA. SARS is a novel coronavirus with some unusual properties. One of the characteristics of SARS is its ability to grow in Vero cells. “In these cells, virus infection results in a cytopathic effect and budding of coronavirus-like particles from the endoplasmic reticulum within infected cells.” SARS has 29,700 nucleotides sequences that’s has been found by serological (antigenic) investigations. The sequence appears to be typical for
References: [1] http://www.cdc.gov/sars/about/fs-SARS.html [2] http://www.microbiologybytes.com/virology/Coronaviruses.html [3] http://www2.cedarcrest.edu/academic/bio/hale/bioT_EID/lectures/SARSvirus.html [4] http://evolution.berkeley.edu/evolibrary/news/060101_batsars [5] http://www.who.int/csr/sars/country/table2004_04_21/en/ [6] http://jasss.soc.surrey.ac.uk/15/1/5.html