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Interesting theory
https://www.iflscience.com/health-and-medicine/delta-variant-may-have-mutated-itself-into-extinction-in-japan-suggest-researchers/ - https://www.iflscience.com/health-and-medicine/delta-variant-may-have-mutated-itself-into-extinction-in-japan-suggest-researchers/
In July,Japan was hit by its largest COVID-19 wave yet. Driven by the introduction of the more infectious Delta variant, cases surged to a record of nearly https://coronavirus.jhu.edu/map.html -
Now, researchers from Japan’s National Institute of Genetics have proposed that the Delta variant may have fallen victim to its own success – the rapidly-mutating strain may have mutated itself into extinction within Japan. According to the https://www.japantimes.co.jp/news/2021/11/18/national/delta-variant-self-destruction-theory/ -
While it would likely not be the first time a virus has "self-destructed" under the weight of its own rapid evolution, it is a phenomenon poorly-documented and a lucky escape for the nation. “We were literally shocked to see the findings,” Inoue told The Japan Times in an interview.
“The delta variant in Japan was highly transmissible and keeping other variants out. But as the mutations piled up, we believe it eventually became a faulty virus and it was unable to make copies of itself. Considering that the cases haven’t been increasing, we think that at some point during such mutations it headed straight toward its natural extinction.”
The idea began when the researchers delved into the genomic profiles of the Delta variant and compared them to the Alpha variants. The expectation was that the Delta variant would be extremely diverse, with multiple lines branching out from the original strain. Instead, they discovered the Delta variant actually had just two major groups, before it seemed to abruptly halt. The Delta variant, at least in Japan, was no longer mutating and diverging into sublineages.
Looking deeper, the researchers examined the viral protein nsp14. This protein has been previously shown to be a proofreading enzyme in RNA viruses – that is to say every time the genetic code of the virus replicates, nsp14 scans through the newly-created genetic material to make sure no errors have cropped up. Mutations in proofreading enzymes spell disaster for organisms that don’t replicate often, so in a virus (which enters the cell, replicates into thousands of virions, and bursts from the host cell in around https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7224694/ -
They found multiple genetic changes at a site within nsp14, called A394V. These mutations appear to contribute to a crippled virus that is unable to replicate, which could explain how the Delta variant simply vanished from Japan in a matter of months.
The theory is certainly interesting but doesn’t quite explain why the crippled virus would outcompete the dominant strain. There are of course other explanations – Japan has https://www.bbc.co.uk/news/world-asia-59342308 -
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