SARS Disease - Assignment Example

During that period, he unwittingly infected others that in turn caused a series of SARS outbreaks in Toronto, Canada and other areas around the world. The transmission of the disease has been quick owing to the little immunity of people to the newly emerged coronavirus. Moreover, it is seen to be most efficient in a health care setting, affecting the health care workers, patients and family members of infected individuals. The high infection rates among the health care workers have illustrated a lack or failure to comply with the Infection Control (IC) measures leading to large-scale outbreaks (Shaw, 2006).

The global spread of this epidemic has also demonstrated the challenge of battling infectious diseases in a globalized world. The forces of globalization-including rapid growth in international trade and travel have amplified their spread and impact ((Hoffmann, 2003) The sudden emergence and the rapid global widespread of this new infectious disease, which defies conventional therapies, poses a great threat to the public health and underscores an urgent need to develop robust strategies to prevent, monitor and contain the disease outbreak.

Based on the Koch's postulates, SARS-Co V, the causative agent of SARS disease, was determined to be a novel member of the order Nidovirales, family Coronaviridae, and genus Coronavirus. It is a large, enveloped positive-sense- single-stranded RNA virus featuring a large genome of 29.7 Kb (Youjun, 2007). As with other coronaviruses, SARS-Co V can be identified on electron microscopy by the presence of a corona of large, distinctive spikes in the envelope (Thomas, 2003). Genomic annotations have revealed that it consists of about 14 functional open reading frames (ORFs).

They encode for three classes of proteins: I) Two large polyproteins (pp1a and pp1ab), which are cleaved into 16 non-structural proteins, essential for viral RNA synthesis, II) Four structural proteins- surface (S), envelope (E), matrix (M), and nucleocapsid (N) proteins, vital for viral assembly, and III) Eight accessory proteins, which confer a selective advantage in an infected host cell. The initial binding of the viral envelope and the host cell membrane is mediated by surface protein (S) (Satija, 2007).

With only 50-60 % nucleotide sequence identity of the SARS- Co V with other known coronaviruses, it is a previously unknown Coronavirus, probably from a non-human host that somehow acquired the ability to infect humans. Various studies have indicated that SARS-Co V spilled over from a wildlife reservoir (probably bats) to the human population via an intermediate host and that rapid virus evolution played a key role in the adaptation of the virus to non-reservoir species (Thomas, 2003).The majority of infections occurred in close contacts of patients indicating that the transmission of the virus was by droplets or by direct and indirect contact.

Epidemiological studies have shown that SARS is moderately rather than highly transmissible. However, in some instances, the so-called "super spreader" patients transmitted the virus to a large number of individuals. The outbreak of the infectious disease has been mainly attributed to these super spreaders and nosocomial amplification. The typical incubation period for the disease ranged from four to six days.