The Delta variant was primarily responsible for the second wave of COVID-19 in the country, accounting for over 80 per cent of new cases, Dr N K Arora, co-chair of Indian SARS-CoV-2 Genomics Consortium said, underlining that the cases may go up if a new, more infectious variant comes.
The variant is also around 40-60 percent more transmissible than its predecessor, Alpha variant, and has already spread to more than 80 countries, including the UK, the US and Singapore.
The Delta variant has mutations in its spike protein, which helps it bind to the ACE2 receptors present on the surface of the cells more firmly, making it more transmissible and capable of evading the body's immunity, Dr Arora said.
"The B.1.617.2, a variant of COVID-19 known as the Delta variant, was first identified in October 2020 in India, and was primarily responsible for the second wave in the country, today accounting for over 80 percent of new COVID-19 cases," he said.
It emerged in Maharashtra and travelled northwards along the western states of the country before entering the central and the eastern states.
On whether it causes more severe disease as compared to other variants, Dr Arora said there are studies that show that there are some mutations in this variant that promote syncytium formation.
"Besides, on invading a human cell, it replicates faster. It leads to a strong inflammatory response in organs like the lungs. However it is difficult to say that disease due to delta variant is more severe. The age profile and the deaths during the second wave in India were quite similar to that seen during first wave," he stated.
Dr Arora said current vaccines are effective against Delta variant as per the studies undertaken by ICMR on the issue.
"The cases may go up if a new, more infectious variant comes. In other words, next wave will be driven by a virus variant to which significant proportion of population is susceptible," he said.
The second wave is still going on. Any future waves will be controlled and delayed if more and more people get vaccinated and most importantly, people follow Covid-19 Appropriate Behavior effectively, especially till a substantial part of our population gets vaccinated, he stressed.
People need to focus on vaccination and adherence to Covid appropriate behavior to manage COVID-19, he added.
There is a need to keep a strict vigil on the emergence of variants of concern and outbreaks so that they can be contained before they spread to a larger region.
The idea is to have a strong network of laboratories to do genomic surveillance of the SARS-CoV-2 and correlate Whole Genomics Sequencing (WGS) data with clinical and epidemiological data to see whether or not a variant is more transmissible, causes more severe disease, escaping immunity or causing breakthrough infections, affecting vaccine efficacy, and diagnosed by current diagnostic tests, he said.
The National Center for Disease Control (NCDC) analyses this data. The entire country has been divided into geographical regions and each lab is given the responsibility of one particular region.
The new mutations/variants of concern are cultured and scientific studies are undertaken to see the impact on infectiousness, virulence, vaccine efficacy and immune escape properties.