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Super transmissible Delta variant primary cause of India’s second wave: Expert panel


New Delhi, June 04: Highly infectious Delta variant of COVID-19, or the B1.617.2, was the primary cause behind the second wave of the COVID-19 pandemic in India, an expert panel has found.

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A new study conducted by National Centre for Disease Control (NCDC) and INSACOG (the consortium of labs undertaking genome sequencing in India) stated that the B.1.617 variant and its lineage B.1.617.2 were primarily responsible for the surge in cases. The study also said that the new variant has 50 per cent more transmissibility than the Alpha or B.1.1.7 variant.

As per the study, genomic sequencing revealed more than 12,200 variants of concern in the country but their presence is miniscule compared to the Delta variant, which replaced all other variants in the second wave.

The study also revelead that the Delta variant that led to several infections even among vaccinated individuals. "B.1.617.2 was over-represented and B.1.1.7 was not even detected in vaccination breakthroughs, suggesting higher breakthrough risk of B.1.617.2 compared to B.1.1.7."

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"The current surge in cases seen over the last two months in some states shows a correlation with the rise in the B.1.617 lineage of SARS CoV-2," the Indian SARS-CoV-2 Consortium on Genomics (INSACOG) said.

The B.1.617 lineage has further evolved into three sub lineages -- B.1.617.1, B.1.617.2 and B.1.617.3. Early data shows B.1.617.2, dubbed Delta by the WHO, has higher transmission advantages over the other two sub-lineages.

B.1.617, initially termed a double mutant, has three new spike protein mutations. Two mutations -- E484Q and L452R -- are in the area important for antibody-based neutralisation.

The third mutation -- P681R in B.1.617 -- along with the reversion of E484Q allows its sub-lineage to be more infectious.

It was found in high levels in genomes sequenced in Maharashtra (2,077), West Bengal (630), Delhi (1,458), Karnataka (225) as of May 28, and accumulates new mutations in spike and other genes, the INSACOG found in the genomes sequenced as of May 28.

The World Health Organisation (WHO) has termed it a ''Variant of Concern''.

B.1.617.1 and B.1.617.3 sub-lineages have two receptor binding domain mutations --- L452R and E484Q. The former has seven spike mutations, while the latter has seven to eight.

In the case of B.1.617.2, it has nine to 10 spike mutations and two receptor binding domain mutations --- L452R and T478K. B.1.6171.1 and B.1.617.2 have higher transmission rate and reduced susceptibility to neutralisation antibodies.

In the case of all the three sub-lineages, it has the potential to reduced antibody efficacy and potential reduced neutralisation by vaccine sera, which, however, remains to be established.

B.1.1.7, also known as the Alpha variant, has 50 per cent increased transmission. It also has increased severity.

The INSACOG is a grouping of 10 national laboratories that was established by the Ministry of Health and Family Welfare on December 25 last year.

It has been carrying out genomic sequencing and analysis of COVID-19 viruses and correlating epidemiological trends with genomic variants.

Genomic variants of various viruses are a natural phenomenon and are found in almost all countries.

The B.1.617.1 and B.1.617.2 variants of the COVID-19, first identified in India, has been named as 'Kappa' and 'Delta' respectively, the World Health Organisation (WHO) announced as it named various variants of the coronavirus using Greek alphabets.

An expert group convened by WHO has recommended labeling using letters of the Greek Alphabet, i.e., Alpha, Beta, Gamma, which will be easier and more practical to discuss by non-scientific audiences, the UN health agency said in a statement.

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