Comparative Review of SARS-CoV-2, SARS-CoV, MERS-CoV, and Influenza A Respiratory Viruses

Abstract

The 2019 novel coronavirus (SARS-CoV-2) pandemic has caused a global health emergency. The outbreak of this virus has raised a number of questions: What is SARS-CoV-2? How transmissible is SARS-CoV-2? How severely affected are patients infected with SARS-CoV-2? What are the risk factors for viral infection? What are the differences between this novel coronavirus and other coronaviruses? To answer these questions, we performed a comparative study of four pathogenic viruses that primarily attack the respiratory system and may cause death, namely, SARS-CoV-2, severe acute respiratory syndrome (SARS-CoV), Middle East respiratory syndrome (MERS-CoV), and influenza A viruses (H1N1 and H3N2 strains). This comparative study provides a critical evaluation of the origin, genomic features, transmission, and pathogenicity of these viruses. Because the coronavirus disease 2019 (COVID-19) pandemic caused by SARS-CoV-2 is ongoing, this evaluation may inform public health administrators and medical experts to aid in curbing the pandemic's progression.

Keywords: COVID-19; MERS-CoV; SARS-CoV; SARS-CoV-2; influenza A virus.

Figure 1

General characteristics of SARS-CoV-2, SARS-CoV, MERS-CoV, and influenza A viruses. (A) Epidemics of SARS-CoV-2, SARS-CoV, MERS-CoV, and influenza A viruses. The timeline, natural reservoirs, total number of deaths, and symptoms of the patients infected with these viruses. (B) Cumulative numbers of cases and deaths caused by SARS-CoV-2, SARS-CoV, MERS-CoV, and influenza A (during the last seasonal flu 2019–2020) viruses. Influenza A virus infected the most people, while SARS-CoV-2 caused the most deaths. (C) Case-fatality rate (CFR) of patients infected with SARS-CoV-2, SARS-CoV, MERS-CoV, and influenza A (the last seasonal flu 2019–2020) viruses stratified by age.

Figure 2

Influenza A evolution. (A) Triple reassortment influenza A viruses of the H1N1 subtype containing avian, swine, and human gene segments. The colored solid genes represent the gene segments as follows: yellow, classical swine A (H1N1) virus; green, North American avian virus; blue, human A (H3N2) virus; gray, Eurasian avian-like swine A(H1N1). (B) Reservoirs and interspecies transmission events of the pathogenic influenza A viruses. Wild birds, domestic birds, pigs, horses, and humans maintain their influenza A viruses. Spillover events occasionally occur, most frequently from wild birds (arrows in green).