Novel coronavirus disease (COVID-19) pandemic: A recent mini review

Abstract

The COVID-19, caused by a novel coronavirus, was declared as a global pandemic by WHO more than five months ago, and we are still experiencing a state of global emergency. More than 74.30 million confirmed cases of the COVID-19 have been reported globally so far, with an average fatality rate of almost 3.0%. Seven different types of coronaviruses had been detected from humans; three of them have resulted in severe outbreaks, i.e., MERS-CoV, SARS-CoV, and SARS-CoV-2. Phylogenetic analysis of the genomes suggests that the possible occurrence of recombination between SARS-like-CoVs from pangolin and bat might have led to the origin of SARS-CoV-2 and the COVID-19 outbreak. Coronaviruses are positive-sense, single-stranded RNA viruses and harbour a genome (30 kb) consisting of two terminal untranslated regions and twelve putative functional open reading frames (ORFs), encoding for non-structural and structural proteins. There are sixteen putative non-structural proteins, including proteases, RNA-dependent RNA polymerase, helicase, other proteins involved in the transcription and replication of SARS-CoV-2, and four structural proteins, including spike protein (S), envelope (E), membrane (M), and nucleocapsid (N). SARS-CoV-2 infection, with a heavy viral load in the body, destroys the human lungs through cytokine storm, especially in elderly persons and people with immunosuppressed disorders. A number of drugs have been repurposed and employed, but still, no specific antiviral medicine has been approved by the FDA to treat this disease. This review provides a current status of the COVID-19, epidemiology, an overview of phylogeny, mode of action, diagnosis, and possible treatment methods and vaccines.

Fig. 1

Total number of confirmed cases and deaths due to Coronavirus disease-2019 (COVID-19). Adapted from COVID-19 dashboard by WHO (https://covid19.who.int/) accessed on December 19, 2020.

Fig. 2

Phylogenetic tree of representative species of SARS-CoV-2, SARS-CoV, and MERS-CoV. Red text highlights zoonotic viruses with pathogenicity in humans and green text highlights common respiratory viruses that circulate in humans. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test (1,000 replicates) was shown next to the branches. Figure adapted from Gorbalenya et al., . The tree was drawn based on the sequence information of following species: Severe acute respiratory syndrome related Bat Hp-betacoronavirus Zhejiang2013 (SARSr-CoV Ratg13), Rousettus bat coronavirus GCCDC1 (RO-Bat-CoV GCCDC1), Rousettus bat coronavirus HKU9 (RO-Bat-CoV HKU9), Eidolon bat coronavirus C704 (Ei-Bat-CoV C704), Pipistrellus bat coronavirus HKU5 (Pi-Bat-CoV HKU5), Tylonycteris bat coronavirus HKU4 (Ty-Bat-CoV HKU4), Middle East respiratory syndrome-related coronavirus (MERS-CoV), Hedgehog coronavirus OC43 (HCoV OC43), Murine coronavirus (MHV), Human coronavirus HKU1 (HCoV HKU1), China Rattus coronavirus HKU24 (ChRCoV HKU24), Pangolin Beta-coronavirus (GD-beta-CoV1), Bat Betacoronavirus 1 (Bat Hp-beta-CoV1), Myodes coronavirus 2JL14 (MrufCoV 2JL14), Human coronavirus NL63 (HCoV NL63), Human coronavirus 229E (HCoV 229E). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 3

Genomic features and structure of SARS-CoV-2. (A) Genomic organization of SARS-CoV-2 reference genome (isolate Wuhan-Hu-1) from NCBI (accession number NC_045512.2). All genomic regions or open-reading frames (ORFs) are presented i.e. untranslated regions at both 5′ and 3′ ends (5′-UTR, 3′-UTR), polyproteins (pp1ab), structural proteins including spike (S), envelope (E), membrane (M) and nucleocapsid (N) proteins. (B) Structure (created with BioRender.com) of SARS-CoV-2 showing its major structural proteins.

Fig. 4

Common symptoms and complication related to the patients of coronavirus disease-2019 (COVID-19). (Figure created with BioRender.com).

Fig. 5

Development of repurposed drugs and vaccines against COVID-19. (1) Inhibition of RNA-dependent RNA polymerase by Favipiravir, Remdesivir and GS-441524. Inhibition of the enzyme halts genomic replication and stops viral dissemination (2) Several drugs have been proposed against helicase but none of them is approved yet (3) Ivermectin dissociates IMP α/β1 (importins) heterodimer, which is responsible for nuclear transport of viral protein cargos, so viral proteins cannot enter into the nucleus to continue vital processes like replication (4) Lopinavir, Ritonavir, Darunavir and Oseltamivir inhibit Main Protease (M^Pro) enzyme which is involved in maturation of viral proteins (5) Inactive and attenuated SARS-CoV-2 can be used for vaccine production (6) Use of spike protein for development of vaccine candidates by different labs and pharma companies. (Figure created with BioRender.com).