Scientists explain the mysterious disappearance of the Delta variant in Japan – RT World News

Japan’s fifth wave of Covid-19 has virtually disappeared so dramatically that some scientists are wondering why it happened. One team suggests that the highly contagious Delta tribe mutated to extinction on the island nation.

In mid-August, Japan experienced a peak in Covid-19 infections and registered over 23,000 new cases a day. Now the metric is just around 170, with deaths attributed to the disease mostly remaining in single digits this month.

The decline has been attributed by many to high vaccination rates, public acceptance of masks and other factors, but some researchers say the decline was uniquely significant compared to other nations with similar conditions.

Ituro Inoue, a geneticist at the National Institute of Genetics, believes Japan had been successful in witnessing the Delta strain mostly exterminating other variants of the SARS-CoV-2 virus before eradicating itself. He explained his team’s theory to the Japan Times this week.

For some time now, Inoue and his scientific colleagues have been researching mutations of SARS-CoV-2 and how they are affected by the protein nsp14, which is essential for the reproduction of the virus.

RNA viruses, such as the one causing Covid-19, tend to have a very high mutation rate, helping them to adapt quickly to changes in the environment. However, this opens the door for a so-called “fault disaster”, when bad mutations pile up and eventually cause complete extinction of a strain. The protein nsp14 appears to offer a form of error proofreading that helps the virus genome stay below the threshold for “failure disaster.”

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In the case of Japan’s fifth wave of Covid-19, the Delta variant nsp14 failed in this job, Inoue believes, based on the genetic study of samples collected from June to October. Contrary to his team’s expectations, there was a lack of genetic diversity, while many specimens had many genetic changes in place called A394V, which is associated with the error-fixing protein.

“We were literally shocked to see the results,” the researcher told the Japan Times. “The Delta variant in Japan was very transferable and [was] keep other varieties out. But as the mutations piled up, we think it eventually became a defective virus and was unable to make copies of itself. “

The theory may be relevant to the former SARS strain, which was identified in 2003, and explains why it did not cause a pandemic. However, this would be difficult to confirm as the outbreak ended relatively quickly and did not result in the massive collection of genetic data needed to test the hypothesis.

It is not clear why Japan had this lucky turn, but nothing comparable happened in other East Asian countries like South Korea, where the populations are genetically close to Japan. Virus mutations similar to those the researchers have identified have been detected in at least 24 countries, Inoue said. He and his team plan to publish a paper outlining their results by the end of November.

Although the theory of natural extinction is confirmed, it is at best a temporary postponement for the Japanese people. New, more successful strains are likely to find their way into the country over time, although quarantine measures and immigration controls may delay the emergence of new varieties in Japan, Inoue believes.

Meanwhile, Tokyo is preparing for a new wave of Covid-19 this winter and preparing to live with the virus. The government reportedly plans to ease travel restrictions by increasing the number of people it allows to enter the country per day from 3,500 to 5,000.

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