The highly transmissible Delta variant of COVID-19 has mutated further to form the 'Delta plus' or 'AY.1' variant but there is no immediate cause for concern in India as its incidence in the country is still low, scientists said.
The new Delta plus variant has been formed due to a mutation in the Delta or B.1.617.2 variant, first identified in India and one of the drivers of the deadly second wave.
Though there is no indication yet of the severity of the disease due to the new variant, Delta plus is resistant to the monoclonal antibody cocktail treatment for COVID-19 recently authorised in India.
"One of the emerging variants is B.1.617.2.1 also known as AY.1 characterized by the acquisition of K417N mutation," Vinod Scaria, clinician and scientist at Delhi's CSIR-Institute of Genomics and Integrative Biology (IGIB), tweeted on Sunday.
The mutation, he said, is in the spike protein of SARS-COV-2, which helps the virus enter and infect the human cells.
According to Public Health England, 63 genomes of Delta (B.1.617.2) with the new K417N mutation have been identified so far on the global science initiative GISAID.
In its latest report on coronavirus variants, updated till last Friday, the health agency said Delta plus was present in six genomes from India as of June 7.
"The variant frequency for K417N is not much in India at this point in time. The sequences are mostly from Europe, Asia and America," Scaria wrote on Twitter.
The earliest sequence of this genome was found in Europe in late March this year.
Noting that the travel histories for the variant are not readily available to make assumptions, Scaria said an important point to consider regarding K417N is the "evidence suggesting resistance to monoclonal antibodies Casirivimab and Imdevimab".
The Union Health Ministry on Tuesday revealed that the Delta Plus variant nullifies the use of monoclonal antibody but asserted that it still not a "variant of concern".
"Delta variant played a major role in 2nd wave. An additional mutation of this variant, known as 'Delta Plus', has been detected and submitted to the global data system. It has been seen in Europe since March and was brought into a public domain on June 13", said member health NITI Aayog Dr VK Paul.
Paul asserted that Delta Plus is a "variant of interest" and has not yet been classified as a "variant of concern" and its presence has to be assessed through Indian SARS-CoV-2 Genomic Consortia (INSACOG).
"As per data available in the public domain, this variant nullifies the use of a monoclonal antibody. We will study and learn more about this variant," he added.
Earlier, the World Health Organization (WHO) had renamed the B.1.617.2 variant of the coronavirus, first identified in India, as the 'Delta variant'.
According to the WHO, in the case of Variants of Concern, a SARS-CoV-2 variant, that meets the definition of a VOI and, through a comparative assessment, has been demonstrated to be associated with one or more of the following changes at a degree of global public health significance-- Increase in transmissibility or detrimental change in COVID-19 epidemiology; or increase in virulence or change in clinical disease presentation; or decrease in the effectiveness of public health and social measures or available diagnostics, vaccines, therapeutics.
A SARS-CoV-2 isolate is a Variants of Interest (VOI) if, compared to a reference isolate, its genome has mutations with established or suspected phenotypic implications, and either: has been identified to cause community transmission/multiple COVID-19 cases/clusters or has been detected in multiple countries; or is otherwise assessed to be a VOI by WHO in consultation with the WHO SARS-CoV-2 Virus Evolution Working Group, as per the global health body.
(With inputs from ANI and PTI)