Covid-19 evolution: One strain overwhelms others

Analysing more than 3,600 strains of Covid-19, two Indian geneticists have found that one particular type of the virus called Type-A2a now sweeps the world replacing even the parental strain found in Wuhan.

Like all viruses, the novel coronavirus-2019 too has evolved into new types over time and during its spread to different parts of the world. Currently, there are 11 types of the virus of which type-O is the ancestral type that was originally reported from China in December 2019. One or a few mutations define the signature of each of these types.

When Nidhan Biswas and Partha Majumder, two scientists at the National Institute of Biomedical Genomics, Kalyani tracked the virus's evolution, they found in most regions only one type (A2a) of Covid-19 has begun to overtake other types.

The scientists collected the genome data from 55 countries up to 6, tapping a global database. Upon closer scrutiny, it showed that Type-O was carried by travelers from China to other parts of the world. Subsequently, it began to evolve inside and outside of China.

Astonishingly, in most parts of the world, only one type (A2a) of Covid-19 proliferates overtaking others. By March-end, the A2a type had nearly replaced all other types and became the dominant type of Covid-19 all over the world.

A similar pattern was seen in India, which too submitted Covid-19 genetic data to the global repository accessed by the duo. Out of the 3600 samples they studied, 35 were Indians.

“The 35 viral sequences belonged to 4 types: the ancestral type-O (5), and derived types A2a (16), A3 (13) and B (1). Two types – A3 and A2a – predominate. All persons infected with type A3 coronavirus have travel history to Iran, while most persons with type A2a have no known travel history to countries outside of India. Therefore, the A2a type is also increasing in its population size within India,” they said in a research paper accepted for publication in the Indian Journal of Medical Research.

The study implies that while engaging in a battle to eradicate or control Covid-19 by a vaccine or any alternative method, the overwhelming presence of Type-A2a has to be taken into account.

“We need to investigate regional differences within India in respect of viral genomic diversity and frequencies of virus types. This will inform the relationship of coronavirus type with host ethnicity, perhaps mediated through differences in frequencies of variants in genes of the immune system among ethnic groups in India,” suggested the NIBG scientists