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Since November 2019, SARS-CoV-2 has been a matter of global concern due to its rapid spread, the millions of deaths it caused, and repeated waves of infections. One after another, many variants of this novel virus have come into existence due to its constant mutability, specifically in the spike glycoprotein region. The tally for variants of concern (VOCs), which already include Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1) and Delta (B.1.617.2), has increased to five with the latest appearance of Omicron (B.1.1.529).
WHO Label | Pango Lineage | Potential Emergence | Number of Countries Affected | Important Spike Mutations | Sequenced Genomes (GISAID) |
Impact of Mutations |
Transmissibility of Variant |
---|---|---|---|---|---|---|---|
Alpha | B.1.1.7 | UK, September 2020 | 170 | N501Y P681H |
11,49,443 | P681H: Slightly increases the S1–S2 cleavage [32]. N501Y: Enhances binding affinity between spike RBD domain and hACE2 receptor [33]. E484K *, L452R * |
~70% increase with respect to wild type |
Beta | B.1.351 | South Africa, May 2020 |
112 | K417N E484K N501Y |
39,604 | K417N: Responsible for antibody-escape property of the virus [34]. N501Y: Same as above. E484K: Reduces antibody neutralisation and is responsible for increased infectivity [35]. |
20–113% increase with respect to wild type |
Gamma | P.1 | Brazil, November 2020 | 80 | K417T E484K N501Y |
1,17,675 | K417T: Responsible for antibody escape property of the virus [34]. N501Y: Same as above. E484K: Same as above. |
~161% increase with respect to wild type |
Delta | B.1.617.2 | India, October 2020 |
105 | L452R T478K P681R |
34,37,588 | T478K: Helps evade neutralising antibodies. Enhances viral infectivity [36]. L452R: Impairs antibody neutralization. Increases viral infectivity [34][37]. P681R: Increases the rate of S1–S2 cleavage, and hence results in enhanced transmissibility [35]. |
|
Omicron | B.1.1.529 | Multiple countries, November 2021 |
- | H655Y N679K P681H E484A Q498R N501Y |
5352 | N501Y: Same as above. H655Y: May be associated with increased transmissibility as it is proximal to the Furin cleavage site, hence aids in increased spike cleavage (CoVariants-GISAID). N679K: Associated with increased transmissibility (CoVariants-GISAID). P681H: Slightly increases the S1–S2 cleavage [32]. E484A: May be associated with immune escape (CoVariants-GISAID). Q498R: Enhances binding affinity with ACE2 receptor in combination with N501Y (CoVariants-GISAID). |
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