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DH Deciphers | Could Delta Plus variant cause another Covid surge?

Just as the Delta variant superseded all other variants, there is concern that Delta+, too, could take over
Last Updated : 17 August 2021, 08:16 IST

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The emergence of a more mutated form of the infectious 'Delta' variant of the novel coronavirus has scientists on edge. Just as the Delta variant superseded all other variants, there is concern that 'Delta Plus', too, could take over. But in India, the middling pace of genomic sequencing means that not enough sequences have been processed to suggest the prevalence of this virus in the general population. Here's what you need to know:

How many cases of 'Delta Plus' have been found worldwide?

Since the first global cases were found on March 29, a total of 156 sequences of the 'Delta Plus' (officially designated B.1.617.2.1 or alternatively as AY.1) have been found across 12 countries. It is a new sub-variant of the widespread 'Delta' variant which scientists blame for being behind the second wave of infections in India.

What makes this variant a concern?

For one, the virus has tried to optimise for transmission and immune escape by the stepwise acquisition of new mutations. In its case, it has acquired eight distinct mutations in its spike protein — two more than the vanilla 'Delta' variant, according to scientists at Delhi’s CSIR-Institute of Genomics and Integrative Biology (IGIB). The spike protein is what the virus uses to gain entry into cells. In many ways, the 'Delta Plus' is a refinement of earlier variants of concern. For one, it has the D614G mutation, which was such a concern during the first wave after scientists found that this mutation allowed the virus to “lock” easily with the ACE-2 receptor of the human host cell. "Understanding this continued evolution is of great importance in mapping the evolutionary landscape of emerging variants,” said Dr Vinod Scaria, a computational biologist at IGIB and an authority on genomics.

How is this variant more dangerous?

Its new spike protein mutations are concerning. One, classified as K417N, potentially allows the 'Delta Plus' to evade an immune response. Scientists at IGIB found that the 'Delta Plus' is potentially resistant to the promising monoclonal antibody cocktail drugs, Casirivimab and Imdevimab, which have been found to be highly effective in treating mild and moderate-symptomed patients. Scientists at IGIB told DH this was determined by “independently testing monoclonal antibodies against specific mutations."

What does this mean?

Since it is potentially resistant to treatments, this variant could potentially trigger another wave or a surge of cases in the months to come.

When was this new variant first seen in India?

According to international viral strain consortiums which track Covid-19 sequences, the first 'Delta Plus' sequence was identified in India on April 4. Eight sequences have been found in six states. As per Nextstrain, an open-source project to document genome data of pathogens, the first three sequences were found in Delhi, Gujarat and Odisha a month ago. Since, the virus has popped up in other states, notably Karnataka, Andhra Pradesh and Tamil Nadu.

Where have the largest numbers been found?

Tamil Nadu has reported the largest number (three sequences found out of 736 genome samples) as of Saturday. In Karnataka, the sole sequence (which originated from Mysuru) was found by Nimhans a week ago, among 1,115 samples. No new 'Delta Plus' sequences have been made public in the last five days.

What is the prevalence of this variant?

Fortunately, its numbers appear to be still limited. The eight examples in India were found among a total of 11,700 sequences processed. But the scale of sequencing in India is modest. At the other end of the spectrum, the United Kingdom, which has been at the forefront of genome sequencing in the Covid-19 era, has processed 4.66 lakh samples, finding 45 'Delta Plus' sequences.

Will the 'Delta Plus' take over from other variants?

Whether the 'Delta Plus' will proliferate and dwarf all other sequences is not yet known. Dr Vishal Rao, an oncologist who is a member of Karnataka’s State Genomic Surveillance Committee, pointed out, for example, that the B.1.617.3, which was detected in India in October 2020, had largely vanished by May 2021. Its five s-protein mutations and nine other mutations in other genes had not been enough to keep the variant alive in the face of other more concerning variants such as the B.1.617.2 'Delta'.

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Published 19 June 2021, 16:38 IST

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