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The Variants of concern(VOC) together with widespread relaxation of COVID-19 appropriate behavior resulted in the 2nd wave of Covid-19 in India.
What is a Variant of Concern?
- The term variant of concern(VOC) is a category assigned to a newly emerged variant of a virus with an increased ability of transmission.
Properties of VOC: The VOC is characterized by three sinister properties:
- Firstly, Increased Transmission Efficiency: In many countries, including India the VOC, by virtue of increased transmissibility, has started off a new wave(s) of epidemic transmission.
- Secondly, Virulence: It is the ability to cause severe/life-threatening disease. The UK variant has the worse virulence. The South Africa and Brazil variants do not seem to have higher virulence.
- Thirdly, Immune to antibodies generated by previous vaccination or infection: Most vaccines were made using antigens made from D614G variant. However, these vaccines show low efficacy on the South African, Brazil and UK variants. Hence, reinfection can occur in spite of immunity provided by earlier D614G infection or vaccination.
How does a new variant emerge?
- If a manuscript is copied by hand repeatedly, there are high chances of spelling errors.
- Similarly, when ‘genetic scripts’ encoded in DNA or RNA are copied repeatedly in virus replication, errors do occur.
- Further, RNA viruses are more error-prone than DNA viruses.SARS-CoV-2 genome is single-stranded RNA and mutations or different variants of a virus occur frequently.
Who detects these variants?
- The ability to detect and track new variants is on the laboratory capacity in whole genome sequencing of viruses.
- In India, the Indian SARS CoV-2 Genomic Consortium (INSACOG), a network of ten competent public-sector laboratories for genomic surveillance was established to detect and track variants.
Nomenclature of SARS-CoV-2 Variants:
- There are three different schemes of nomenclature of SARS-CoV-2 variants.
- The widely used one is the ‘Phylogenetic Assignment of Global Outbreak Lineages’(PANGOLIN) that uses a hierarchical system based on genetic relatedness – an invaluable tool for genomic surveillance.
- It uses alphabets (A, B, C, P) and numerals starting with 1. Variant lineages are at the emerging edge of the pandemic in different geographies. Lineage B is the most prolific.
SARS Cov-2 Variants:
- The three most frequent Variant of Concern(VOC) are named by their geography of origin:
- ‘U.K. variant’ for B.1.1.7;
- ‘South Africa variant’ for B.1.351;
- and ‘Brazil variant’ for P.1.
Note: The original pandemic virus (founder variant) was Wu.Hu.1 (Wuhan virus). In a few months, variant D614G emerged and became globally dominant.
Source: The Hindu