Other variations of Covid-19 have been shown to cause fewer symptoms, carry immune-escaping mutations, or be even more fast-spreading
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The Delta coronavirus variant could mutate itself into extinction and already has done so in Japan, according to scientists.
It comes as Japan is recording just 140 cases of the virus each day despite having been badly hit by the more infectious Delta strain three months ago.
Cases peaked at around 23,000 a day in August but, since then, numbers have dropped significantly – on Friday, only 16 new cases were recorded in its capital Tokyo.
One of the theories for the sudden fall in the Delta infection rate is that continued mutation has caused it to effectively fizzle out.
While mutations can make a virus even more potent, the makeup of it changes over time as it replicates and genes undergo “copying errors”, which can lead to “evolutionary dead ends”.
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Researchers led by the National Institute of Genetics, Mishima, Japan, found lots of genetic changes before a sudden stop in the evolution process.
Ituro Inoue, a genetics professor at the institute, told The Japan Times : “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.”
Prof Inoue said the virus would still be spreading if Delta were “alive and well”.
Dr Simon Clarke, Head of Division of Biomedical Sciences and Biomedical Engineering at University of Reading, explained too many mutations could lead to the virus dying out.
He told The Sun: “The virus accumulates too many mutations and therefore stops being able to replicate.
“When you get a virus like that, it just dies out. It’s like a person that never has children, their genetic material stops, end of the road.
“That doesn’t mean that everyone else stops producing children.”
Dr Clarke added: “It is possible for the strain to stop evolving, but only when it stops replicating, which these Japanese scientists think has happened – a virus has evolved to stop replicating.
“You need somehow to break the chains of transmission and some mutations will make the virus unviable – they become evolutionary dead ends.
“However, that will only occur in a very small subset of cases.
“There will still be a lot of coronavirus around that is capable of infecting people and will do just that until we have sufficient immunity or we can break the chains of transmission, which is what happened with SARS because it wasn’t as good at transmission as Covid-19.”