Analysis of the Delta Variant B.1.617.2 COVID-19

Abstract

With the delta variant of COVID-19, known as B.1.617.2, quickly ramping up infections around the world, we need to understand what makes this variant more contagious. One study has reported that the delta variant is 60% more transmissible than the alpha variant. As of August 2021, the delta variant has quickly become the dominant strain. Despite countries like the US, where most of the population is vaccinated, COVID-19 has made a resurgence in infections. Collectively, as a country, we ask: is it more deadly? What makes it more "contagious" or "transmissible"? This review article delves into the information we already know about the delta variant and how it compares with the other SARS-CoV-2 variants. The current vaccine companies like AstraZeneca, Pfizer/BioNTech, and Moderna have reported that their vaccines can provide protection against this variant but with a slightly reduced efficacy. In this article, we do a comprehensive review and summary of the delta B.1.617.2 variant and what makes it more contagious.

Keywords: B.1.617.2; COVID-19; delta variant.

Figure 1

SARS-CoV-2 structure and binding schematic. (A) Native resting state of the ACE-II receptor on the host cell surface. (B) Spike protein binding to the ACE-II receptor. (C) Viral fusion with the host cell membrane. Host cell proteases cleave the spike protein into S1 and S2 subunits. S1 is responsible for binding to ACE-II, while S2 is responsible for viral fusion and entry. Upon S1 binding ACE-II, the HR 1 and 2 subunits form the 6-helix bundle (6-HB) in order to bring the viral particle close to the host cell to allow for fusion and entry [11].

Figure 2

Representation of the spike protein mutations found in the B.1.6172 variant. NTD = N-terminal domain, RBD = receptor-binding domain, RBM = receptor-binding motif, SD1 = subdomain 1, and SD2 = subdomain 2.