Delta sub-lineages unlikely to be more contagious than Delta itself: Insacog

The sub-lineages, AY.1 and AY.2, of the Delta variant (B.1.617.2) are declining globally, with near-zero cases in the last week of June in the UK and the US where they were most frequently detected

The sub-lineages of the highly contagious Delta variant of the Sars-CoV-2 virus, identified in India, that causes coronavirus disease (Covid-19), are unlikely to be more transmissible than Delta itself, according to the latest Indian Sars-CoV-2 Genomics Consortium (Insacog) bulletin.

Representational image. (Satish Bate/HT PHOTO)

The sub-lineages, AY.1 and AY.2, of the Delta variant (B.1.617.2) are declining globally, with near-zero cases in the last week of June in the UK and the US where they were most frequently detected, according to the summary of the cumulative data based on whole genome sequencing of Covid-19 positive cases released by the department of biotechnology, government of India, on July 9.

“They also continue to be below 1% in available sequences from June in India. It is likely that neither AY.1 nor AY.2 is more transmissible than Delta. 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),” said the bulletin.

A new sub-lineage AY.3 has been identified, which has primarily been detected in the US with single reclassified cases in UK and India. However, there are no known significant properties of this mutation, but since it is a Delta variant of concern sub-lineage, Insacog will continue to monitor it.

Meanwhile, scientists have found that the proportion of known variants of concern that are in circulation in India remain unchanged from the preceding week. 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 the Delta variant.

Among other known variants, alpha variant prevalence has declined further in India and globally. Beta is also at very low levels in India at this time. Gamma and Lambda are not seen in over 10,000 community samples sequenced by Insacog since May.

“In summary, Delta variant and its sub-lineages are the only VOC in India at this time. Continuing outbreaks across India are attributable to Delta, susceptible population, and opportunities for transmission. Public health measures to reduce transmission and vaccination remain critical,” said the bulletin.