Variants of SARS-CoV-2

There are many variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (COVID-19).Some are considered or have been declared to be of particular importance because they may increase transmissibility increase virulence or reduce the effectiveness of vaccines directed against them.These variants contribute to the persistence of the COVID-19 pandemic.As of May 2023, only Omicron and its own variant [indiscernible] have been designated by the World Health Organization as circulating variants of concern.

Overview

The origin of SARS-CoV-2 has not been determined.However, the emergence of SARS-CoV-2 may be the result of a recombination event between bat SARS-like CoVs and pangolin CoVs via cross-species transmission.The earliest available genomes of the SARS-CoV-2 virus were collected from patients in December 2019, and Chinese researchers compared these early genomes with bat and pangolin coronavirus strains to estimate the ancestral human coronavirus Type; the determined ancestral genome type is marked "S" and its dominant derived type is marked "L" to reflect the mutant amino acid change. Independently, Western researchers performed a similar analysis but labeled the ancestral type as "A" and the derived type as "B".Type B mutations into other types, including B.1, the progenitor of the variant of major global concern, labeled by the World Health Organization as alpha, beta, gamma, delta and omicron variants in 2021.In the early stages of a pandemic, the relatively low number of infections (compared to the later stages of the pandemic) lead to fewer opportunities for mutations in the viral genome and thus fewer chances for divergent variation to occur.Because the mutations occur less frequently, it is also uncommon to observe mutations in the S protein in the region of the receptor-binding domain (RBD) that interacts with ACE2.

Over time, the evolution of the SARS-CoV-2 genome (via random mutations) resulted in mutated samples of the virus (i.e., genetic variation) that were observed to be more transmissible, being naturally selected.Notably, the Alpha and Delta variants were observed to be more transmissible than previously identified strains.Some SARS-CoV-2 variants are considered worrisome because they maintain (or even increase) their replicative fitness in the face of rising population immunity either through recovery from infection or through vaccines Inoculate.Some worrisome variants show mutations in the RBD of the S protein.The table below presents information and relative risk levels for current and previously prevalent variants of concern (VOCs) .Unless otherwise stated, these intervals assume a 95% confidence or confidence level.At this time, due to limited availability of research data, all estimates are approximate.There was no change in test accuracy for Alpha, Beta, Gamma, and Delta,Some mAbs retained neutralizing antibody activity.PCR tests continue to detect Omicron variants.