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.
