deLemus Test

The dynamic epidemiology of coronavirus disease 2019 (COVID-19) since its outbreak has been a result of the continuous evolution of its etiological agent, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Within the first 2 years of this pandemic, the World Health Organization (WHO) has already announced 4 variants of concern (VOC), namely alpha (B.1.1.7), beta (B.1.351), gamma (P.1), and delta (B.1.617.2), together with numerous variants of interest (VOI). The latest lineage to be designated a VOC would be omicron (B.1.1.529), from which a diverse variant soup is generated. From the original BA.1 strain of November 2021 to the most recent XBB and BQ.1 strains of late 2022, each omicron subvariant has successively proliferated and outcompeted its once dominant antecedent.

The emergence of all these variants has brought along many novel mutations that continue to fine-tune the fitness of the virus, leading to its persistent global circulation. Recent emerging variant (EV) data retrieved from GISAID, as of 17 January 2023, has revealed that the top 4 most rapidly spreading lineages are the BA.1.1.22, CH.1.1, XBB.1.5, and BQ.1.1 variants, among which XBB.1.5 has been found to be especially prevalent in the US, making up of more than 40% of its sequence coverage in early January 2023.

Spike Glycoprotein

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The spike glycoprotein of SARS-CoV-2 is a trimeric type I viral fusion protein that binds the virus to the angiotensin-converting enzyme 2 (ACE2) receptor of a host cell.[9] It is composed of 2 subunits: the N-terminal subunit 1 (S1) and C-terminal subunit 2 (S2), within which multiple domains lie. The S1 region facilitates ACE2 binding and is made up of an N-terminal domain (NTD), a receptor-binding domain (RBD), and 2 C-terminal subdomains (CTD1 and CTD2), while the downstream S2 region is responsible for mediating virus-host cell membrane fusion.

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