Indian SARS-CoV-2 Genomics Consortium (INSACOG), a consortium of 28 national laboratories to monitor the genomic variations in the COVID-19 virus, has said that the sub-lineages of delta variant are unlikely to be more transmissible than the parent.

These two delta sub-lineages - AY.1 and AY.2 - also continue to be below 1 per cent in available sequences from June in India, the INSACOG said.

"Delta sub-lineages AY.1 and AY.2 are declining globally with near zero cases in the last week of June in either UK or US, where they were most frequently seen. They also continue to be below 1 per cent in available sequences from June in India. It is likely that neither AY.1 nor AY.2 is more transmissible than Delta," the INSACOG said in its weekly bulletin.

There are no indications of rising trend in the four clusters in Ratnagiri and Jalgaon in Maharashtra, Bhopal in Madhya Pradesh and Chennai in Tamil Nadu.

Meanwhile, AY.3 has been identified as a new Delta sub-lineage, defined by ORF1a: I3731V common AY.1 mutations except for S: K417, it said.

The AY.3 is "primarily seen in the US with single reclassified cases in UK and India", it added.

There are no known significant properties of this (AY.3) mutation, but since it is a Delta VOC sub-lineage, INSACOG will continue to monitor it, the consortium of national labs said.

"Delta is the dominant lineage for new cases across all parts of India in recent samples and remains the most rapidly rising lineage globally. New data points to efficacy of vaccination against severe disease by Delta Variant," the INSACOG said.