The Global Emergency of Novel Coronavirus (SARS-CoV-2): An Update of the Current Status and Forecasting

Abstract

Over the past two decades, there have been two major outbreaks where the crossover of animal Betacoronaviruses to humans has resulted in severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV). In December 2019, a global public health concern started with the emergence of a new strain of coronavirus (SARS-CoV-2 or 2019 novel coronavirus, 2019-nCoV) which has rapidly spread all over the world from its origin in Wuhan, China. SARS-CoV-2 belongs to the Betacoronavirus genus, which includes human SARS-CoV, MERS and two other human coronaviruses (HCoVs), HCoV-OC43 and HCoV-HKU1. The fatality rate of SARS-CoV-2 is lower than the two previous coronavirus epidemics, but it is faster spreading and the large number of infected people with severe viral pneumonia and respiratory illness, showed SARS-CoV-2 to be highly contagious. Based on the current published evidence, herein we summarize the origin, genetics, epidemiology, clinical manifestations, preventions, diagnosis and up to date treatments of SARS-CoV-2 infections in comparison with those caused by SARS-CoV and MERS-CoV. Moreover, the possible impact of weather conditions on the transmission of SARS-CoV-2 is also discussed. Therefore, the aim of the present review is to reconsider the two previous pandemics and provide a reference for future studies as well as therapeutic approaches.

Keywords: ACE2; COVID-19; SARS-CoV-2; diagnosis; epidemiology; inhibitors; pneumonia; temperature and humidity; therapeutics strategies; transmission.

Figure 1

Classic subgroup clusters of coronaviruses within the family Coronaviridae, subfamily Orthocoronavirinae and the respective genera: Alphacoronavirus, Betacoronavirus, Gammacoronavirus and Deltacoronavirus.

Figure 2

Origin and evolution of (A) SARS-CoV, (B) MERS-CoV and (C) SARS-CoV-2 in the various hosts. Initially all viruses existed in diverse bat species as CoV-related viruses (SARSr-CoV, MERSr-CoV and SARSr-CoV-2); sequential mutations and recombinations allow them to adapt to intermediate hosts and finally humans [15].

Figure 3

Typical coronavirus virion structure and proteins. The coronavirus genome encodes a (S) spike glycoprotein, an (E) envelope glycoprotein, a (M) membrane glycoprotein, a (N) nucleocapsid phosphoprotein and a (HE) hemagglutinin-esterase glycoprotein.

Figure 4

Graphic genome structures of SARS-CoV-2, SARS-CoV and MERS-CoV. Each coronavirus (CoV) genome is schematically represented in the order of 5′-ORF1a-ORF1b-S-E-M-N-3′. The coronavirus genomes encode two replicase polypeptides pp1a and pp1ab translated from ORF1a and ORF1b; four structural genes encoding for four structural proteins including (S) spike, (M) membrane, (E) envelope and (N) nucleocapsid proteins. The single-stranded RNA genomes of SARS-CoV-2 (~29.8 kb), SARS-CoV (~29.7 kb) and MERS-CoV (~30.1 kb) harbor two large genes, the ORF1a (red) and 1b (blue) genes encoding accessory genes (nsps 1–16, shades of red and blue). Encoded nonstructural proteins: 16 nsps (nsp1-nsp16) in SARS-CoV-2, SARS-CoV and MERS-CoV. Along with structural proteins (S, E, M and N), the 3′-terminus of the SARS-CoV-2 and SARS-CoV genomes contain eight accessory proteins (3a, 3b, p6, 7a, 7b, 8b, 9b and orf14 and 3a, 3b, p6, 7a, 7b, 8a, 8b and 9b, respectively) while MERS-CoV genome contains only five (3, 4a, 4b, 5 and 8b). The genes encoding accessory proteins are unique in different coronaviruses in terms of number, genomic organization, sequence and functions (data extracted from [35,49,57]).

Figure 5

Monthly temperature (degree C) reanalysis maps using ECMWF dataset of all the world. The temperatures at 2-m height, obtained from ERA-interim datasets (https://climatereanalyzer.org/), have been processed to extract monthly means maps for the period November 2019 to February 2020. ERA-interim is a global reanalysis of recorded climate observations over the past 3.5 decades. It is presented as a gridded data set at approximately 0.7 degrees spatial resolution and 37 atmospheric levels. ERA-interim is produced by the European Center for Medium-Range Weather Forecasts (ECMWF) (https://climatereanalyzer.org/).

Figure 5

Monthly temperature (degree C) reanalysis maps using ECMWF dataset of all the world. The temperatures at 2-m height, obtained from ERA-interim datasets (https://climatereanalyzer.org/), have been processed to extract monthly means maps for the period November 2019 to February 2020. ERA-interim is a global reanalysis of recorded climate observations over the past 3.5 decades. It is presented as a gridded data set at approximately 0.7 degrees spatial resolution and 37 atmospheric levels. ERA-interim is produced by the European Center for Medium-Range Weather Forecasts (ECMWF) (https://climatereanalyzer.org/).

Figure 6

Organ involvement confirmed by clinical features or bioptic sampling in COVID-19 patients (A). Table describing main observed disorders (B).

Figure 7

Median times, in days, from the onset of symptoms to death, to hospitalization, from hospitalization to death with and without intensive care unit (ICU)-admittance (Report based on available data on July 9th, 2020 collected from Istituto Superiore di Sanità, ISS).

Figure 8

Schematic representation of SARS-CoV-2 infection and virus-induced human immune system response. Proposed drugs directed both towards specific SARS-CoV-2 molecular targets and biologic processes are highlighted: inhibitors of SARS-CoV-2 fusion/entry targeting ACE2 receptor, spike protein, TMPRSS2 or HR1 and HR2 epitopes and clathrin-mediated endocytosis (I); molecules against SARS-CoV-2 main protease (II); molecules against viral genome replication (III); CRISPR technologies targeting SARS-CoV-2 RNA genome (IV); modulators of SARS-CoV-2 induced inflammatory response (V) and human neutralizing antibodies (VI). ACE2, angiotensin-converting enzyme 2; TMPRSS2, type 2 transmembrane serine proteases; RdRp, RNA-dependent RNA polymerase; HR1, heptad repeat 1; HR2, heptad repeat 2; HR2P, heptad repeat 2-derived peptides; EK1, a modified OC43-HR2P peptide. Adapted from [223].