Delta variant may have mutated into extinction in Japan, researchers suggest

In July, Japan was hit by its largest wave of COVID-19 to date. Driven by the introduction of the more contagious Delta variant, the cases rose to a record of almost 26,000 daily cases, more than four times the wave before it. Then as quickly as the cases went up, they went down again, and within two months of the peak, the cases are now around 140 per day. Scientists are aware that the rapid rise is due to the Delta variant, but they fail to understand how the cases fell again while other nations continued to fight the virus.

Now researchers at Japan’s National Institute of Genetics have suggested that the Delta variant may have fallen victim to its own success – the rapidly mutating strain may have mutated to extinction in Japan. According to Japan times, Ituro Inoue and colleagues believe that the virus has received a mutation in its error-correcting protein, causing genetic errors to accumulate in such a way that they can no longer replicate.

While it might not be the first time a virus has “self-destructed” under the weight of its own rapid evolution, it is a poorly documented phenomenon and a happy escape for the nation.

“We were literally shocked to see the results,” Inoue told the Japan Times in an interview.

“The delta variant in Japan was highly transferable and kept other variants out. But as the mutations piled up, we believe it eventually turned into a buggy virus and was unable to make copies of itself. When you consider that cases have not increased, we think that at some point during such mutations they were heading straight for natural extinction. ”

The idea arose when researchers looked at 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 off from the original variety. Instead, they discovered that the Delta variant actually only had two main groups before it seemed to stop abruptly. The delta variant, at least in Japan, was no longer mutated and diverged into sublines.

Upon closer inspection, the researchers examined the viral protein nsp14. This protein has already been shown to be a proofreading enzyme in RNA viruses – that is, every time the virus’s genetic code replicates, nsp14 scans the newly created genetic material to make sure that no errors have occurred. Mutations in proofreading enzymes mean disaster for organisms that don’t replicate often, that is, a virus (which enters the cell, replicates into thousands of virions, and roughly bursts out of the host cell.) 10 hours) a faulty enzyme would be a catastrophe.

They found several genetic changes at a site within nsp14 called A394V. These mutations appear to contribute to a crippled virus that cannot replicate, which could explain how the Delta variant simply disappeared from Japan within a few months.

The theory is certainly interesting, but it doesn’t fully explain why the crippled virus would displace the dominant strain. There are other explanations, of course – Japan has one of the highest Vaccination rates and people are extremely disciplined when wearing masks, which means outbreaks in populated areas are likely to be stopped quickly. However, it certainly points to a possible reason for the decline in cases and even suggests a possible therapeutic against RNA viruses.