What makes Delta COVID variant so transmissible?

Bhubaneswar: In a recent interview, Dr N K Arora, co-chair, Indian SARS-CoV-2 Genomics Consortium (INSACOG), explained what makes the Delta COVID-19 variant so transmissible.

Q. The Delta variant has been in focus as a global concern. What makes this variant so virulent?

B.1.617.2, a variant of COVID-19 is known as the Delta variant. It 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. It emerged in Maharashtra and travelled northwards along 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 percent 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.

Q. Does it also cause more severe disease as compared to other variants?

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.

Q. Is Delta Plus variant more aggressive than Delta variant?

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, Japan but AY.2 is less prevalent. The variant is still being studied for its transmissibility, virulence, and vaccines escape characteristics.

Q. Are the vaccines effective against the Delta variant?

Yes, current vaccines are effective against Delta Variant as per the studies undertaken by ICMR on the issue.

Q. Some parts of the country are still witnessing a spurt in the number of cases. Why?

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.

Q. Can future waves be prevented?

A virus begins infecting a part of the population, which is most susceptible and also exposed to the infection. 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, next wave will be driven by a virus variant to which significant proportion of 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.

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