Study Reveals SARS-CoV-2 Jumped from Bats to Humans without Much Change

A study conducted by a collaboration between researchers in the UK, US, and Belgium shows that since December 2019 and for the first 11 months of the SARS-CoV-2 pandemic, there has been very little 'important' genetic change observed in the hundreds of thousands of sequenced virus genomes.

Using HyPhy, a state-of-the-art analytical framework at Temple University, Philadelphia, the research team was able to tease out the signatures of evolution embedded in the virus genomes. The study's first author Dr. Oscar MacLean from the University of Glasgow explains that this does not mean no changes have occurred, as mutations of no evolutionary significance accumulate and ‘surf' along the millions of transmission events like they do in all viruses.

Prof. David L. Robertson from the University of Glasgow Centre for Virus Research in Scotland said that the reason for the ‘shifting of gears' of SARS-CoV-2 in terms of its increased rate of evolution at the end of 2020, associated with more heavily mutated lineages, is because the immunological profile of the human population has changed. He added that the virus towards the end of 2020 was increasingly coming into contact with existing host immunity as the numbers of previously infected people increased. This will select for variants that can dodge some of the host response, together with the evasion of immunity in longer-term infections in chronic cases (e.g., in immunocompromised patients), these new selective pressures are increasing the number of important virus mutants.

For more details, read the article in Science Magazine.