The sub-lineages of Delta variant of the coronavirus – AY.1 and AY.2 – are not likely to be more transmissible than the Delta strain itself, said the Indian Sars-CoV-2 Genomics Consortium, or INSACOG. The body is a consortium of 10 laboratories that conducts genome sequencing of Covid-19 infections.

“They [AY.1 and AY.2] also continue to be below 1% in available sequences from June in India,” INSACOG said in a bulletin. The AY.1 sub-lineage is commonly known as the Delta plus variant.

INSACOG added that there was also no indication that the cases of the sub-lineages were rising in four clusters in Madhya Pradesh’s Bhopal, Chennai in Tamil Nadu, and Maharashtra’s Ratnagiri and Jalgaon.

The bulletin said the cases of two sub-lineages were declining globally with almost no infections recorded in the last week of June in either the United Kingdom and the United States – the two countries where the mutations were most frequently seen.

The consortium also said that a new sub-lineage of the Delta variant, AY.3, has been identified. The AY.3 is characterised by another mutation, K417N, which is also found in the Beta variant, the bulletin said.

“It [AY.3] is primarily seen in the US with single reclassified cases in UK and India,” it said. “There are no known significant properties of this mutation, but since it is a Delta VOC [variant of concern] sub-lineage, INSACOG will continue to monitor it.”

INSACOG said that the Delta variant was the most dominant lineage in the country and remained the most rapidly rising one globally. It said that the Alpha variant prevalence has declined further in India as well as globally. The Gamma and Lambda variants are not seen in over 10,000 community samples sequenced since May, INSACOG said.

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

The World Health Organization had designated Delta as a variant of concern on May 11 and predicted that it will rapidly become the dominant strain across the world. In June, WHO Chief Scientist Soumya Swaminathan had said the Delta variant was becoming the dominant variant globally “because of its significantly increased transmissibility”.

The Delta variant was responsible for the devastating second wave of the pandemic in India, a government study showed in June.

India is still recovering from the aftermath of the second wave, which at its peak in May saw more than 4 lakh daily cases, and thousands of deaths every day. Several states experienced crippling shortages of oxygen, hospital beds, medical supplies and vaccines, causing citizens to take to social media to ask for help.

The cases have declined now. India recorded 41,806 new coronavirus cases on Thursday morning, pushing the tally of infections since the outbreak of the pandemic in January last year to 3,09,87,880. The number was 7.7% higher than Wednesday’s count of 38,792 cases. India’s toll rose to 4,11,989 as it recorded 581 more deaths in the last 24 hours.