Table 1.
Comparison between the three viruses (SARS-CoV, MERS-CoV, and COVID-19) in terms of their epidemiology, morphogenesis, and pathogenesis
| COVID-19 | MERS-CoV | SARS-CoV | |
|---|---|---|---|
| Epidemiology | |||
| Date of emergence | December 2019 [5] | June 2012 [4] | November 2002 [3] |
| Area of emergence | Wuhan, China [5] | Jeddah, Saudi Arabia [4] | Guangdong, China [3] |
| Animal host | Bats [7] | Camels and bats [7] | Bats, palm civets, and raccoon dogs [7] |
| Human–human transmission | + [8] | + [8] | + [8] |
| Nosocomial transmission | + [8] | + [8] | + [8] |
| Risk to healthcare workers | + [8] | + [8] | + [8] |
| Morphogenesis | |||
| Nature of the genome | Single-stranded positive-sense RNA genomes, linear, unimolecular, infectious, 26–32 kb in length, capped, polyadenylated, and structurally polycistronic [7, 9–14] | ||
| Presence of an envelope | + [7, 9, 11, 12, 15] | ||
| Morphology | Spherical, bacilliform, decorated with large (15–20 nm) surface projections, crown-shaped appearance [7, 9, 11] | ||
| Virion size | Spherical: 120–160 nm; bacilliform: 75–90 nm * 170–200 nm [9, 13] | ||
| Genome size | 29.9 kb [16] | 27.9 kb [13] | 30.1 kb [13] |
| Family | Coronaviridae [7, 9, 11] | ||
| Subfamily | Orthocoronaviridae [13, 15] | ||
| Genus | Betacoronavirus [7, 9, 10, 13] | ||
| Subgenus | Sarbecovirus [12, 15] | Merbecovirus [13] | Sarbecovirus [15] |
| Essential structural proteins | Spike (S) glycoprotein, small envelope (E) protein, matrix (M) protein, and nucleocapsid (N) protein [10, 11] | ||
| Coding strategy | Two-thirds of the viral RNA is translated into two large polyproteins, and the remainder of the viral genome is transcribed into a nested set of subgenomic mRNAs [10] | ||
| Pathogenesis | |||
| Cellular infection | Binding of spike protein to angiotensin-converting enzyme 2 (ACE2) [7, 12] | Binding of spike protein to dipeptidyl peptidase-4 [7] | Binding of spike protein to angiotensin-converting enzyme 2 (ACE2) [7, 12] |
| Virulence factor | Spike (S) glycoprotein, others: nonstructural protein 1 (nsp1), nsp3, nsp7, nsp17, ORF3a, E protein, M protein, and the nucleocapsid protein [9, 12, 13, 17, 18] | ||
ACE2 angiotensin-converting enzyme 2, COVID-19 coronavirus disease 2019, MERS-CoV Middle East respiratory syndrome coronavirus, mRNA messenger RNA, nsp nonstructural protein, ORF3a open reading frame 3a, RNA ribonucleic acid, SARS-CoV severe acute respiratory syndrome coronavirus