Coronavirus Disease 2019-COVID-19

Abstract

SUMMARYIn recent decades, several new diseases have emerged in different geographical areas, with pathogens including Ebola virus, Zika virus, Nipah virus, and coronaviruses (CoVs). Recently, a new type of viral infection emerged in Wuhan City, China, and initial genomic sequencing data of this virus do not match with previously sequenced CoVs, suggesting a novel CoV strain (2019-nCoV), which has now been termed severe acute respiratory syndrome CoV-2 (SARS-CoV-2). Although coronavirus disease 2019 (COVID-19) is suspected to originate from an animal host (zoonotic origin) followed by human-to-human transmission, the possibility of other routes should not be ruled out. Compared to diseases caused by previously known human CoVs, COVID-19 shows less severe pathogenesis but higher transmission competence, as is evident from the continuously increasing number of confirmed cases globally. Compared to other emerging viruses, such as Ebola virus, avian H7N9, SARS-CoV, and Middle East respiratory syndrome coronavirus (MERS-CoV), SARS-CoV-2 has shown relatively low pathogenicity and moderate transmissibility. Codon usage studies suggest that this novel virus has been transferred from an animal source, such as bats. Early diagnosis by real-time PCR and next-generation sequencing has facilitated the identification of the pathogen at an early stage. Since no antiviral drug or vaccine exists to treat or prevent SARS-CoV-2, potential therapeutic strategies that are currently being evaluated predominantly stem from previous experience with treating SARS-CoV, MERS-CoV, and other emerging viral diseases. In this review, we address epidemiological, diagnostic, clinical, and therapeutic aspects, including perspectives of vaccines and preventive measures that have already been globally recommended to counter this pandemic virus.

Keywords: COVID-19; One Health; SARS-CoV-2; diagnosis; emerging coronavirus; therapy; vaccines.

FIG 1

S-gene SplitsTree analysis. Shown is the spike (S) glycoprotein gene-based phylogenetic analysis (SplitsTree 4.0) of SAR-CoV-2 isolates (39 isolates). The SARS-CoV-2 isolates were analyzed with related CoVs from past human outbreaks and of animal origin, including MERS-CoV, bovine coronavirus, canine coronavirus, bat coronaviruses, bat-SL-SARS-CoV, and equine CoV. The analysis includes all five defined subgenera of Betacoronaviruses, namely, Sarbecovirus, Embecovirus, Merbecovirus, Nobecovirus, and Hibecovirus. The isolates in the gray area are from the current outbreak of SARS-CoV-2 from around the world. The nearest neighbors of SARS-CoV-2 are the bat-SL-CoV, encircled in yellow.

FIG 2

SARS-CoV-2 virus structure.

FIG 3

World map depicting the current scenario of COVID-19. Shown are countries, territories, or regions with reported confirmed cases of SARS-CoV-2 as of 13 May 2020. Different colors indicate different WHO designated geographical regions with the number of confirmed cases. The WHO region-wise total number of confirmed cases is depicted in different color strips. The leading information on the confirmed cases and deaths from all six WHO designated regions are depicted in circled balloons. The numbers of COVID-19 cases and fatalities on three major cruise ships are also depicted. (Based on data from the WHO at https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200513-covid-19-sitrep-114.pdf?sfvrsn=17ebbbe_4; updated numbers of cases, deaths, and patients recovered can be found at https://gisanddata.maps.arcgis.com/apps/opsdashboard/index.html#/bda7594740fd40299423467b48e9ecf6.)

FIG 4

Bar graph and pie chart for cases and deaths. Shown are laboratory-confirmed cases and deaths in China and the rest of the world due to SARS-CoV-2. (A) SARS-CoV-2 confirmed cases in the top five affected countries from each WHO designated region, where maximum casualties were reported to WHO until 13 May 2020. (B) Total numbers of deaths and cases in China only. (C) Total number of cases worldwide by region.

FIG 5

Timeline depicting the significant events that occurred during the SARS-CoV-2/COVID-19 virus outbreak. The timeline describes the significant events during the current SARS-CoV-2 outbreak, from 8 December 2019 to 13 May 2020.

FIG 6

Potential transmission routes for SARS-CoV-2.

FIG 7

Coronavirus origins. Coronavirus is the most prominent example of an emerging virus that has crossed the species barrier from wild animals to humans, like SARS and MERS. The origin of SARS-CoV-2 is also suspected to be from an intermediate animal host. The possibility of crossing the species barrier again for the fourth time cannot be ruled out.