NEW DELHI: There could as many as 11 types of SARS CoV 2 -- the virus behind the global COVID-19 pandemic -- but a type that is more adapted to infect human lungs has emerged as the dominant type driving the outbreak worldwide, including in India, two Indian scientists have found.
The scientists attached with the National Institute of Biomedical Genomics under the department of biotechnology of the Union government have discovered that from O or ancestral type of virus that originated from Wuhan, China, there are 10 more types that have evolved over time but a type named A2a started to overtake other types.
By the end of March, this A2a type had nearly replaced all other types and became the dominant type of SARS-CoV-2, noted the scientists in their research paper set to be published in the Indian Journal of Medical Research by the Indian Council of Medical Research.
The study is based on detailed analyses of RNA sequences of over 3600 coronaviruses collected from 55 countries from the time COVID-19 cases were first reported in December 2019 to April 6 this year.
The prevalence of A2a viruses in some countries and regions could be as high as 80 per cent, while in India it stands at 45 per cent, the research has suggested.
The observations in the study might have major implications.
"Our research clearly indicates that in terms of infectivity and transmission A2a looks the most capable. So, as a vaccine or any other intervention is developed against the virus, the major fight has to be against this particular type," said Partha Majumdar, one of the two scientists behind the major finding.
The scientists have analysed that the reason this particular type is sweeping across regions could be that it acquired a change in its RNA sequence, which alters a component -- an amino acid alteration from aspartic acid to glycine of the spike protein -- that facilitates the virus' entry into lung cells.
As human lung cells produce a protein called ACE2 on their surface, the spike protein of the coronavirus first clings to this surface protein ACE2 and then another protein takes action and promotes the entry of the virus into the lung cell.
"The more efficiently a type of virus can bind and enter, the more successful it will be to propagate itself. The A2a type of the coronavirus has gained this efficiency because of the amino acid change to glycine from aspartic acid. All other types of SARS-CoV-2 possess aspartic acid," the researchers found.
Similar changes were shown to increase the efficiency of infection of the previous coronavirus SARS-CoV that had caused an outbreak about ten years ago and caused a large number of deaths.