The outbreak of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2): A review of the current global status

Abstract

There is currently an ongoing worldwide pandemic of a novel virus belonging to the family of Coronaviruses (CoVs) which are large, enveloped, plus-stranded RNA viruses. Coronaviruses belong to the order of Nidovirales, family of Coronavirinae and are divided into four genera: alphacoronavirus, betacoronavirus, gammacoronavirus and deltacoronavirus. CoVs cause diseases in a wide variety of birds and mammals and have been found in humans since 1960. To date, seven human CoVs were identified including the alpha-CoVs HCoVs-NL63 and HCoVs-229E and the beta-CoVs HCoVs-OC43, HCoVs-HKU1, the severe acute respiratory syndrome-CoV (SARS-CoV), the Middle East respiratory syndrome-CoV (MERS-CoV) and the novel virus that first appeared in December 2019 in Wuhan, China, and rapidly spread to 213 countries as of the writing this paper. It was officially named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by the international committee on taxonomy of viruses (ICTV) and the disease's name is COVID-19 for coronavirus disease 2019. SARS-CoV-2 is very contagious and is capable of spreading from human to human. Infection routes include droplet and contact, and aerosol transmission is currently under investigation. It is associated with a respiratory illness that may cause severe pneumonia and acute respiratory distress syndrome (ARDS). SARS-CoV-2 became an emergency of international concern. As of July 12, 2020, the virus has been responsible for 12,698,995 confirmed cases and 564,924 deaths worldwide and the number is still increasing. Up until now, no specific treatment has yet been proven effective against SARS-CoV-2. Since the beginning of this outbreak, several interesting papers on SARS-CoV-2 and COVID-19 have been published to report on the phylogenetic evolution, epidemiology, pathogenesis, transmission as well as clinical characteristics of COVID-19 and possible treatments agents. This paper is a systematic review of the available literature on SARS-CoV-2. It was performed in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) and aims to help readers access the latest knowledge surrounding this new infectious disease and to provide a reference for future studies.

Keywords: COVID-19; Emergence; Prevention; SARS-CoV-2; Transmission; Treatment.

Fig. 1

PRISMA flowchart of literature search strategy.

Fig. 2

Emergence of human coronaviruses: As of July 12, 2020, seven CoVs are known to be human pathogens including the alpha-CoVs HCoVs-NL63 (1200-1500) and HCoVs-229E (1700-1800) and the beta-CoVs HCoVs-OC43 (1890), HCoVs-HKU1 (1950), severe acute respiratory syndrome-CoV (SARS-CoV) (2002), Middle East respiratory syndrome-CoV (MERS-CoV) (2012) and the novel SARS-CoV-2 (2019).

Fig. 3

SARS-CoV-2 situation update worldwide: As of July 12, 2020, 12,698,995 cases of COVID-19 have been reported in the world including 564,924 deaths. The most affected continent is the America with 6,685,097 confirmed cases and 286,796 deaths on this day (https://www.ecdc.europa.eu/).

Fig. 4

SARS-CoV-2 life cycle in infected cells and inhibition targets: SARS-CoV-2 begins its life cycle by binding of the S protein presented on the surface of the virus to the cellular receptor ACE2 on the target cell. After receptor binding, the S protein changes conformation, facilitating viral envelope fusion with the infected cell membrane through endocytosis. SARS-CoV-2 then releases its genetic material into the host cell. Genomic RNA is translated into viral replicase polyproteins pp1a and 1ab, which are then cleaved into small products by viral proteinases. By discontinuous transcription, the polymerase produces a series of subgenomic mRNAs that are translated into viral proteins. The positive-sense genomic RNA is then packaged into a ribonucleocapsid and is assembled into viral particles in the ER and Golgi apparatus where they undergo maturation. Virions are finally transported via small vesicles and released out of the cell through exocytosis. Inhibition targets are presented in red.