Table 1 Comparison regarding the change in transmissibility, virulence and antigenicity in the wild-type SARS-CoV-2 and its emerging variants

Wild-type SARS-CoV-2

First originated in Wuhan, China

Binding of receptor binding domain (RBD) of the spike (S) protein to the human angiotensin converting enzyme 2 (hACE2), mediating the viral entry

None

Noor et al. (2022)

Alpha variant (of B.1.1.7 lineage)

Originated in the UK. Transmissibility increased by 29% (160 countries) as of June 2021

The emerging variants of the Wuhan strain of SARS‐CoV‐2 possess the key mutations, especially in the RBD of the spike (S) protein that interacts with (hACE2 may instigate significant alterations in the interaction between SARS-CoV-2 and the host. Such mutations may accelerate the mechanism of RBD binding to the hACE-2 of the S protein, enhances glycosylation of this S protein at the antigenic sites, which in turn, results in the proteolytic cleavage of the S protein with concomitant entry into the host cells. New VOCs may take their entry even more easily imparting increased viral replication frequency/ viral shedding, resulting in more lethality with serious tissue impairment as well as hyper inflammation. Enhancement of viral replication and evasion of the neutralizing antibodies are another strategies of SARS-CoV-2 pathogenesis

Total 23 mutations, Key mutations: H69-V70del, N501Y, and P681H, conferring viral entry

Noor et al. (2022) Campbell et al. (2021), Kumar et al. (2022)

Beta variant (B.1.351 lineage)

Originated in South Africa. Transmissibility increased by 25% (113 countries) as of June 2021

Key mutation: N501Y within the RBD domain of S protein, conferring n RBD high affinity to bind hACE-2

Noor et al. (2022), Campbell et al. (2021), Kumar et al. (2022)

Gamma variant (of P.1 lineage)

Originated in Brazil. Transmissibility increased by 38% (64 countries) as of June 2021

Total 17 mutations, conferring viral entry

Noor et al. (2022), Campbell et al. (2021), Kumar et al. (2022)

Delta variant (B.1.617.2 lineage)

Originated in India. Transmissibility increased by 97% (62 countries) as of June 2021

Key mutations: E484Q, L452R, P681R, conferring viral entry. L452R also facilitates viral entry and antibody evasion.

Noor et al. (2022), Campbell et al. (2021), Kumar et al. (2022)

Omicron variant (B.1.1.529 lineage). The Omicron variant has mutated into three lineages: BA.1, BA.2, and BA.3, as of February 2022

Originated in South Africa. This variant of concern (VOC) had spread across 105 countries as of January 10, 2021

More than 50 mutations (Thirty mutations in spike (S) protein, alteration of 9 amino acids), conferring viral entry; and the evasion of neutralizing antibody

Noor et al. (2022), Campbell et al. (2021), Sanyaolu et al. (2022)