JOIN USCovid-19: Experts keep eagle eye on Delta variant sub-lineages
Experts are closely monitoring the Delta variant of the novel coronavirus to see if any of the 32 sub-lineages of the variant, 15 of which were found in Karnataka, will evolve into a more concerning form amid fears of a third wave of Covid-19 taking off in the state.
Recent sequencing efforts in Bengaluru show that the number of mutations in some sub-lineages is reducing. However, experts of the state Genomics Surveillance Committee added a note of caution, saying that these reductions could presage a transformation of the virus.
Dr Vishal Rao, Dean, HCG Hospital, and a member of the committee, specified that recent iterations of the Delta variant’s sub-lineages AY.4 and AY.12, which comprise 11 per cent and 4 per cent of all samples sequenced in the state, are showing fewer mutations in their spike proteins. The virus uses its spike protein to bind with human host cells, so any changes there dictate the behaviour of the virus.
In one example, researchers had found that while a specific spike-protein mutation (G142D) was found in 26 per cent of the AY.4 sequences in Karnataka, it was found in only 1.3 per cent of AY.12 sequences.
“Since mutations are reducing in these areas, we could assume that the ‘Delta’ variant is becoming weaker,” Dr Vishal said. “However, infectious disease experts say that this reduction in mutations, by its own nature, cannot be construed as being ‘safe’ because the reduction of mutations does not translate into less virulence.”
Instead, Rao said, it could signify that the virus is working in other domains to start changing itself. “It could be trying to create a new form,” he said.
Experts see a cautionary tale in the emergence of a new variant of interest in South Africa, C.1.2, which is associated with reduced neutralisation sensitivity as well as increased transmissibility. “The C.1.2 has some low level of vaccine evasion and there is concern that a similar change could happen to any of the Delta sub-lineages, although Delta, for the most part, has been responsive to vaccines,” said one expert.
The committee nevertheless believes that more time is needed to collect sufficient data points to make determinations about where these sub-lineages are headed.
“While a large amount of sequencing has been done, Covid-19 case numbers have declined in the past few weeks, so the sample base for sequences has come down. There is also the natural life cycle of the virus, two to three weeks, which means that time is needed to make assessments about the virus,” said Professor Satyajit Mayor, Director, National Centre for Biological Sciences (NCBS), and a committee member.
Disappearance of Delta+
Experts said that the disappearance of the more enhanced Delta+ sub-lineages (AY.1 and AY.2) from Karnataka in recent weeks also means that we need to step back from discussions about high infectivity or prevalence and focus on circumstances of transmission.
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