Since the illness was first reported in Asian in 2003, the severe acute respiratory syndrome (SARS) has been studied in depth, especially at the microscopic level. Within a short period, the disease spread over all the continents except Africa, but was successfully contained. Nevertheless, it is still one of the major threats to the world health because it has a rapid rate of infection, spreading and a very high mortality rate (Peiris, Lai, Poon, et al 2003).
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SARS is a viral disease caused by the SARS-associated coronavirus (SARS-CoV) of the viral order Nidovirales, Family Coronaviridae, Subfamily Coronaviridae, Genus Bectacornavirus and Species SARS Coronavirus. The virus belongs to the Group IV ((+)ssRNA), meaning that is it a positive single stranded RNA virus (Thiel 2012). The SARS Coronavirus is a large virus, with about 29kb long genome. So far, 13 genes and 14 proteins have been identified by molecular studies conducted since 2003. In addition, studies have shown that the genomes 5’UTR and 3’UTR have about 265 and 342 nucleotides respectively (Snijder et al. 2003). Like other members of the coronavirus family, the SARS virus expression begins with a single translation of 1a and 1b polyproteins from two large ORFs (Rota et al. 2003).
According to McBride and Fielding (2012), most of the protein functions of the genome products of the virus have been elucidated and are well known. For instance, the two large ORFs, 1a and 1b encode an enzyme replicas, as well as the codes for the proteins that end up making the structure of the virus. Although major studies have been conducted to examine these sections, the functions of the 8 proteins are not well understood.
Like other members of the family, the SARS virus expresses the ORF1a polyprotein (pp1a) and the pp1b polyprotein joined together (Rota et al 2003). The large proteins are then cleaved into 16 smaller functional subunits by proteins PLpro and 3CLpro (Thiel 2012). After this, the normal replication process of positive single stranded RNA viruses takes place, producing a large number of viruses that are highly infectious.
The disease resulting from an infection with the SARS virus is simply known as SARS. The initial symptoms are fever, headache and muscular pain. After about 2 days to 2 weeks of the first symptoms, the patients show a number of other conditions associated with respiratory system, which include pneumonia, cough and dyspnea (Thiel 2012). Hematologically, the patients experience a rapid reduction in the volume of lymphocytes within their circulatory systems.
The highest recorded mortality rate due to the condition was recorded in 2003 and was about 50% among the people aged 50 and above (Thiel 2012). In younger generations, the mortality rate was often low, mostly less than 45% in various nations in Asia (Thiel 2012).
In conclusion, SARS is a viral disease with a high rate of spreading and a high mortality rate. Alongside Ebola and H1N1, the virus poses a major threat to the population in the modern world.
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