Delta variant 40-60% more transmissible than Alpha variant

The Delta variant of the novel coronavirus is around 40-60 per cent more transmissible than the Alpha variant, said Dr NK Arora, the chief of the Covid-19 working group of the National Technical Advisory Group on Immunization (NTAGI).

“It is around 40-60 per cent more transmissible than its predecessor (Alpha variant) and has already spread to more than 80 countries, including India, UK, US, Singapore and others,” Dr Arora said.

Explaining the reason behind the higher transmissibility of the Delta variant, Dr Arora said, “The Delta variant has mutations in its spike protein that 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.”

The Delta variant was first identified in October last year in India. It is believed to be primarily responsible for the second wave in the country, accounting for over 80 percent of 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.

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 the north-eastern and southern parts of the country.

Earlier, WHO director-general Tedros Adhanom Ghebreyesus said a shortage of vaccines in poor countries was exacerbating the spread of the Delta variant.

Are current vaccines effective against Delta variant?
The current vaccines are effective against the Delta variant as per the studies by ICMR, the government said in a press bulletin on Monday.

“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,” the government said.

Is the Delta Plus variant more aggressive than Delta variant?
“It is difficult to say that the Delta Plus variant is more severe,” Dr N K Arora 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 has also been 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 immune escape characteristics.

“Delta sub-lineages AY.1 and AY.2 are declining globally with near-zero cases in the last week of June in either the UK or US, where they were most frequently seen. They also continue to be below 1 per cent in available sequences from June in India. It is likely that neither AY.1 nor AY.2 is more transmissible than Delta,” INSACOG, a government panel involved in genome sequencing of coronavirus, said.

INSACOG said the Delta variant (B.1.617.2) was the dominant lineage for new cases across India in recent samples and remains the most rapidly rising lineage globally. India Today