Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of coronavirus (CoV) disease 2019 (COVID-19). This study compared the genome, mutations, and infectivity/transmissibility of SARS-CoV-2 with selected betacoronaviruses (beta-CoVs). This study further examined the origin, risk factors, and outbreaks caused by beta-CoVs. We searched the following databases for relevant studies: PubMed, Google Scholar, and the World Health Organization COVID-19 database. A close relationship between SARS-CoV-2 and SARS bat-like CoV RaTG13 (98.9%) was found at the amino acid level, followed by pangolin CoVs. Non-synonymous mutations occur at high frequencies in the open reading frame (ORF) 1ab, spike (S) protein, and nucleocapsid. Mutations P323L and D614G in the RNA-dependent RNA polymerase (RdRp) and S protein, respectively, occur at a high frequency globally. Mutations at position 3037 in the nonstructural protein (Nsp) 3, 14408 (RdRp), and 23403 (S) confer transmissibility to SARS-CoV-2. SARS-CoV-2 has higher infectivity and transmissibility than SARS-CoV, which shares the same receptor. Although bats are confirmed reservoirs, intermediate hosts are currently unknown. Smoking, old age, diabetes, cardiovascular diseases, and hypertension have all been associated with COVID-19. Within six months of its outbreak, COVID-19 was reported in all countries worldwide, whereas SARS was reported in 28 countries and Middle East respiratory syndrome (MERS) in 5 countries. However, the fatality rate of MERS (65%) was higher than that of COVID-19 (4.9%) and SARS (6.6%). Identifying the SARS-CoV-2 intermediate hosts will help prevent future outbreaks. Attention should be given to the pangolin CoVs. Variations in the S gene may confer transmissibility and infectivity.
Highlights
Betacoronaviruses have been responsible for three outbreaks that are of public health significance over the past two decades
Within six months of its outbreak, COVID-19 was reported in all countries worldwide, whereas SARS was reported in 28 countries and Middle East respiratory syndrome (MERS) in 5 countries
The SARS-CoV-2 genomeis highly similar to the strain RaTG13 of bat origin. This was followed by pangolins based on amino acid similarities of the whole genome, S, M, E, and N
Summary
Betacoronaviruses (beta-CoVs) have been responsible for three outbreaks that are of public health significance over the past two decades. Coronavirus (CoV) disease 2019 (COVID-19) first appeared in December 2019, and the World Health Organization (WHO) announced the name of the new epidemic on February 11, 2020. Its name was changed by the International Committee on Taxonomy of Viruses to severe acute respiratory syndrome CoV2 (SARSCoV-2)[1,2]. Other organisms in the genus of public health concern are SARS-CoV and Middle East respiratory syndrome (MERS)CoV1. MERS-CoV caused the MERS outbreak in 2012–2015, resulting in 1,621 cases and 584 deaths[3]. SARS-CoV was responsible for the SARS outbreak, spreading across 37 countries in 2002– 2003 resulting in 8,000 cases and 774 fatalities[3,4]. Other human CoVs (HCoVs) are NL63 and 229E of the Alphacoronavirus genus and OC43 and HKU1 of the genus Gammacoronavirus[1,3,4]
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