COVID Delta variant around 40-60% more transmissible than Alpha variant, says INSACOG Co-Chair N K Arora

COVID Delta variant around 40-60% more transmissible than Alpha variant, says INSACOG Co-Chair N K Arora

New Delhi, July 20, 2021

The COVID Delta variant (B.1.617.2) is around 40-60% more transmissible than the Alpha variant, says Indian SARS-CoV-2 Genomics Consortium (INSACOG) co-chair N K Arora.

In a recent interview, Dr Arora elaborated about the Standard Operating Procedure (SOP) for testing and follow-up on variants, what makes the Delta variant so transmissible and how genomic surveillance can help contain its spread. He also reiterated the importance of COVID-appropriate behaviour.

INSACOG is a consortium of 28 laboratories of the Ministry of Health & Family Welfare, Dept. of Biotechnology, Indian Council of Medical Research (ICMR) and Council of Scientific and Industrial Research (CSIR) for whole-genome sequencing in the context of the COVID-19 pandemic. INSACOG was established on December 25, 2020.

Asked about the recent expansion of INSACOG, he stressed the need to keep a strict vigil on the emergence of variants of concern and outbreaks so that they could be contained before spreading to a larger region. It had started as a consortium of 10 laboratories and added 18 more.

“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.

“Then the National Centre 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. We have formed 180-190 clusters with around four districts in each cluster. Regular random swab samples and samples of patients who develop severe illness, vaccine breakthrough infections and other atypical clinical presentations, are collected and sent to regional laboratories for sequencing. The current capacity of the country is to sequence over 50,000 samples per month. Earlier it was approximately 30,000 samples,” he added.

About the mechanism for testing and follow-up on variants, he said India has a well-established mechanism of Integrated Disease Surveillance. The IDSP coordinates sample collection and transportation from the districts/sentinel sites to Regional Genome Sequencing Laboratories (RGSL). These labs are responsible for genome sequencing and identification of Variants of Concerns (VOC)/Variants of Interest (VOI), Potential Variants of Interest and other mutations.

Information on VOC/VOI is directly submitted to the Central Surveillance Unit for clinical-epidemiological correlation in coordination with State Surveillance Officers. The samples are then sent to the designated biobanks.

RGSLs, upon identification of a genomic mutation that could be of public health relevance, submit it to the Scientific and Clinical Advisory Group (SCAG). SCAG thereafter discusses the Potential Variants of Interest and other mutations with experts and, if necessary, recommends to the Central Surveillance Unit for further investigation.

Sharing of information and clinical-epidemiological correlation is done by IDSP, a unit of NCDC, along with the Ministry of Health, the Indian Council for Medical Research, the Department of Biotechnology, Council for Scientific and Industrial Research and state authorities.

Finally, 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.

About the Delta variant, Dr Arora said the B.1.617.2 was first identified in October 2020 in India, and was primarily responsible for the second wave in the country, today accounting for over 80% of the new COVID-19 cases. It emerged in Maharashtra and travelled northwards along with the western states of the country before entering the central and the eastern states.

It 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. It is around 40-60% more transmissible than its predecessor (Alpha variant) and has already spread to more than 80 countries, including the UK, the USA, Singapore and so on.

Some studies 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 the first wave,” he said.

About the Delta Plus variant being more aggressive than the Delta variant, he said, “The Delta Plus variant—AY.1 and AY.2—has so far been detected in 55-60 cases across 11 states, including Maharashtra, Tamil Nadu, and Madhya Pradesh. AY.1 is also found in countries like Nepal, Portugal, Switzerland, Poland and Japan but AY.2 is less prevalent. The variant is still being studied for its transmissibility, virulence and vaccine escape characteristics. Current vaccines are effective against Delta Variant as per the studies undertaken by ICMR,” he added.

“Though there is a significant dip in the number of cases in most parts of the country, some regions are witnessing a high Test Positivity Rate (TPR), particularly in the north-eastern parts of the country and several districts in the southern states. Most of these cases could be due to the Delta variant,” he added.

On prevention of future waves, he said a virus begins infecting the most susceptible and exposed part of the population. It diminishes after it successfully infects a large proportion of the population and strikes back when the immunity developed in the people post-natural infection fades.

The cases may go up if a new, more infectious variant comes. In other words, the next wave will be driven by a virus variant to which a significant proportion of the population is susceptible.

“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-appropriate behaviour effectively, especially till a substantial part of our population gets vaccinated. People need to focus on vaccination and adherence to COVID Appropriate Behaviour to manage COVID-19,” he added.


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