According to a study conducted in the United Kingdom, the number of secondary infections produced by a person infected with the Delta variant (B.1.617.2) of the SARS-CoV-2 virus increases by 97 per cent when compared to the virus initially identified in Wuhan. It found that this variation, which was discovered in India initially, is far more communicable than any other form.

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The study

Eurosurveillance, a European journal for infectious illnesses, evaluated data submitted by 64 nations to the worldwide SARS-CoV-2 genome sequencing database GISAID. It discovered that the effective reproductive number rose by 29% for the first reported Alpha variation (B.1.1.7) from the United Kingdom, 25% for the first reported Beta variant (B.1.351) from South Africa, and 38% for the first reported Gamma (P.1) variant from Brazil. The researchers discovered that two of the six variations of interest increased the effective reproductive number statistically significantly - the Kappa variant (B.1.617.1) by 48 per cent and the Eta variant (B.1.525) by 29 per cent.

Transmissibility: What does a 97% rise mean?

This means that if the previous virus transmitted between two persons, the Delta variety would spread between four people. The effective reproductive number is determined by two variables: the R0 (R-nought) or fixed reproductive number for each virus, and population immunity. The study discovered a cumulative increasing trend in the variations across 64 nations.

Findings

The researchers discovered that the Delta version had a "clear competitive edge" over the Alpha, Beta, and Gamma varieties. The Delta variation's effective reproduction number rose by 55% when compared to Alpha, 60% when compared to Beta, and 34% when compared to the Gamma version.

This was congruent with the discovery of a 42 per cent rise in the Delta variant's secondary attack rate (the chance of infection happening in a specific unit, such as a home or among close contacts) in epidemiological studies conducted in the United Kingdom. Additionally, physicians from India have consistently said that the secondary attack rate was significantly higher during the second wave of the epidemic in April-May, when virtually every member of a family became sick if one person became ill – something that had not before occurred.

According to the experts, in order to contain the pandemic, given the rapid spread of the Delta variety in a number of nations, tougher controls will need to be implemented for a longer length of time. The spread of the disease will also strain healthcare systems, as was seen in India during the second wave when patients battled to obtain hospital beds.

Delta vs other variants

Delta variants are up to 50% more [transmissible] than Alpha variants, while Alpha variants are much more [transmissible] than non-variants. While the number of infections in India is significantly fewer at the moment, the Centre has urged states and union territories not to relax their guard. According to UK researchers, increased transmissibility also increases the threshold for herd immunity, resulting in a rise in vaccine coverage objectives.

After the massive second wave of illnesses in April-May, India's population immunity is already rather high. I think that India's population-level immunity is already above 80%. To avoid fatalities, immunisation should now be aimed at patients with comorbidities and pregnant women. Vaccination of youngsters must also be implemented to ensure the safe reopening of schools.

The researchers have, however, placed a cautionary note. The report concluded:

“The convergent evolution of mutations linked with increased transmissibility or immune escape demonstrates that variations will very certainly continue to arise in response to selection forces. As the COVID-19 epidemic continues, the development of novel variations jeopardises vaccine efficacy and necessitates a continuous review of existing diagnostic, therapeutic, and vaccination strategies.

Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.

The author is a practising super specialist from New Delhi.