Lessons learned 1 year after SARS-CoV-2 emergence leading to COVID-19 pandemic

Abstract

Without modern medical management and vaccines, the severity of the Coronavirus Disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome (SARS) coronavirus 2 (SARS-CoV-2) might approach the magnitude of 1894-plague (12 million deaths) and 1918-A(H1N1) influenza (50 million deaths) pandemics. The COVID-19 pandemic was heralded by the 2003 SARS epidemic which led to the discovery of human and civet SARS-CoV-1, bat SARS-related-CoVs, Middle East respiratory syndrome (MERS)-related bat CoV HKU4 and HKU5, and other novel animal coronaviruses. The suspected animal-to-human jumping of 4 betacoronaviruses including the human coronaviruses OC43(1890), SARS-CoV-1(2003), MERS-CoV(2012), and SARS-CoV-2(2019) indicates their significant pandemic potential. The presence of a large reservoir of coronaviruses in bats and other wild mammals, culture of mixing and selling them in urban markets with suboptimal hygiene, habit of eating exotic mammals in highly populated areas, and the rapid and frequent air travels from these areas are perfect ingredients for brewing rapidly exploding epidemics. The possibility of emergence of a hypothetical SARS-CoV-3 or other novel viruses from animals or laboratories, and therefore needs for global preparedness should not be ignored. We reviewed representative publications on the epidemiology, virology, clinical manifestations, pathology, laboratory diagnostics, treatment, vaccination, and infection control of COVID-19 as of 20 January 2021, which is 1 year after person-to-person transmission of SARS-CoV-2 was announced. The difficulties of mass testing, labour-intensive contact tracing, importance of compliance to universal masking, low efficacy of antiviral treatment for severe disease, possibilities of vaccine or antiviral-resistant virus variants and SARS-CoV-2 becoming another common cold coronavirus are discussed.

Keywords: COVID-19; Coronavirus; Diagnostics; Pandemic; Pathogenesis; SARS-CoV-2; Treatment; Vaccines.

Figure 1.

Chronology of events leading to the COVID-19 pandemic.

Figure 2.

(A) Whole genome phylogenetic tree of betacoronaviruses. The tree was constructed by maximum likelihood method with the best-fit substitution model GTR + F+R5 using IQTree2. Bootstrap values were calculated by 500 trees. SARS-CoV-2 are highlighted in red. Human coronavirus 229E (NC_002645) was used as outgroup. (B) Whole genome phylogenetic analysis showing different clades of SARS-CoV-2. The tree was constructed by maximum likelihood method with the best-fit substitution model TIM2+F + I using IQTree2. Bootstrap values were calculated by 500 trees. Clade information as inferred by Nextstrain or Pango lineage are shown. HK1 is the predominant lineage found during the 2020 summer peak in Hong Kong, while W4 is the predominant lineage that is found in almost all local cases in Hong Kong since November 2020. The reference genome Wuhan-Hu-1 (GenBank accession number MN908947.3) is used as the root of the tree.

Figure 3.

Histology of lung tissue section. (A) Image of hematoxylin and eosin (H&E) stained lung tissue shows diffuse alveolar exudation and inflammatory infiltration; a medium size blood vessel containing thrombus which almost blocks the entire lumen (arrow heads). Scale bar = 500 µm. (B) Magnified H&E image shows severe hyaline membrane formation in the alveolar space (open arrows). Scale bar = 200 µm. (C) Magnified H&E image shows severe mononuclear immune cell infiltration in the alveolar space (solid arrows). Scale bar = 50 µm. (D) Immunofluorescence stained SARS-CoV-2 nucleocapsid (N) antigen in alveoli (white arrows); the insert image showing a few N protein expressing cells in a small bronchial lumen. Scale bar = 100 µm.

Figure 4.

Typical changes of COVID-19 pneumonia on lung computed tomography showing bilateral multifocal patchy ground glass opacities: (A) transverse view; (B) coronal view.