SARS coronavirus outbreaks past and present—a comparative analysis of SARS-CoV-2 and its predecessors

Abstract

The Coronavirus Disease 2019 (COVID-19), a pneumonic disease caused by the SARS Coronavirus 2 (SARS-CoV-2), is the 7th Coronavirus to have successfully infected and caused an outbreak in humans. Genome comparisons have shown that previous isolates, the SARS-related coronavirus (SARSr-CoV), including the SARS-CoV are closely related, yet different in disease manifestation. Several explanations were suggested for the undetermined origin of SARS-CoV-2, in particular, bats, avian and Malayan pangolins as reservoir hosts, owing to the high genetic similarity. The general morphology and structure of all these viral isolates overlap with analogous disease symptoms such as fever, dry cough, fatigue, dyspnoea and headache, very similar to the current SARS-CoV-2. Chest CT scans for SARS-CoV-2, SARS-CoV and MERS-CoV reveal pulmonary lesions, bilateral ground-glass opacities, and segmental consolidation in the lungs, a common pathological trait. With greatly overlapping similarities among the previous coronavirus, the SARS-CoV, it becomes interesting to observe marked differences in disease severity of the SARS-CoV-2 thereby imparting it the ability to rapidly transmit, exhibit greater stability, bypass innate host defences, and increasingly adapt to their new host thereby resulting in the current pandemic. The most recent B.1.1.7, B.1.351 and P.1 variants of SARS-CoV-2, highlight the fact that changes in amino acids in the Spike protein can contribute to enhanced infection and transmission efficiency. This review covers a comparative analysis of previous coronavirus outbreaks and highlights the differences and similarities among different coronaviruses, including the most recent isolates that have evolved to become easily transmissible with higher replication efficiency in humans.

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“… 7 ). Typically, coronaviruses have club-shaped spike projections on the virion surface, resembling the solar corona, hence, the name Coronavirus (Refs 8 , 9 ). Being in the same genus as the SARS-CoV and MERS-CoV, the SARS-CoV-2 closely resembles the general structure and genomic configuration of SARS-CoV (Ref.…”

“… 10 ) with 94.4% similarity in the amino acid sequence for open reading frame (ORF) 1a and 1b (Ref. 8 ). The SARS-CoV-2 genome is approximately 29.9 kilobases (kb) in size with a typical 5’ cap and a poly (A)-3'tail to mimic an mRNA for translation (Ref.…”

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“…It was postulated to be associated with the dromedary camel 6 . To date, the origin of SARS‐CoV‐2 is still being debated, with sources pointing to bats as the natural reservoir, akin to the related SARS‐CoV identified in the year 2002 7,8 …”

“…Similar to SARS‐CoV and MERS‐CoV, the SARS‐CoV‐2 is a member of the beta (β) genus, thus sharing a certain degree of similarity in general morphology and structure as its counterparts, especially concerning the SARS‐CoV with an astonishing 79% genetic identity and 94.4% amino acid similarity 9,10 . The SARS‐CoV‐2 infection, like its counterparts, affects mainly the respiratory system, giving symptoms such as fever, dry cough, fatigue, dyspnoea, headache, gastrointestinal discomfort, diarrhoea, conjunctivitis, skin discolouration or rashes, anosmia and dysgeusia 8 . However, the major contributor to the rapid progression of COVID‐19 lies within the large numbers of asymptomatic cases of SARS‐CoV‐2 infection in addition to the patients with the aforementioned disease symptoms 11,12 …”

“…9,10 The SARS-CoV-2 infection, like its counterparts, affects mainly the respiratory system, giving symptoms such as fever, dry cough, fatigue, dyspnoea, headache, gastrointestinal discomfort, diarrhoea, conjunctivitis, skin discolouration or rashes, anosmia and dysgeusia. 8 However, the major contributor to the rapid progression of COVID-19 lies within the large numbers of asymptomatic cases of SARS-CoV-2 infection in addition to the patients with the aforementioned disease symptoms. 11,12 Currently, the persistent symptoms of COVID-19 pose serious health and quality of life concerns of the COVID-19 survivors.…”