The fifth wave of Covid-19 in Japan has almost disappeared so fast that some scientists are confused about the reason for its occurrence. A team believes that the highly contagious Delta strain mutated and became extinct in this island country.
In mid-August, Japan experienced the peak of Covid-19 infection, recording more than 23,000 new cases every day. Now, the indicator is only around 170, and most of the deaths attributed to the disease this month remain in the single digits.
Many people attribute this decline to high vaccination rates, public acceptance of masks and other factors, but some researchers say that this decline is unique compared to other countries with similar conditions.
Ituro Inoue, a geneticist at the National Institute of Genetics, believes that Japan is fortunate to have witnessed the eradication of the Delta strain after the eradication of other variants of the SARS-CoV-2 virus.he explain His team’s theory was reported to The Japan Times this week.
For some time, Inoue and his scientists have been studying the 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, like the viruses that cause Covid-19, tend Has a very high mutation rate, which helps them quickly adapt to changes in the environment.However, this is the so-called “Wrong disaster” When bad mutations pile up and eventually lead to the complete extinction of the strain.The protein nsp14 seems to provide a form of error proofreading that can help keep the viral genome below the threshold “Wrong disaster.”
Inoue believes that in the fifth wave of Covid-19 in Japan, the nsp14 of the Delta variant failed to complete this work, which is based on genetic research on specimens collected from June to October. Contrary to his team’s expectations, there is a lack of genetic diversity, and many samples have many genetic changes in the site named A394V, which are related to error repair proteins.
“Seeing these findings, we were really shocked,” The researcher told the Japan Times. “The Delta variant in Japan is highly contagious and [was] Keep other variants. But with the accumulation of mutations, we believe that it will eventually become a defective virus, and it cannot replicate itself. “
This theory may be related to the previous SARS strain discovered in 2003, explaining why it did not cause a pandemic. But this is difficult to confirm, because the epidemic ended relatively quickly and did not result in a large collection of genetic data to test hypotheses.
It is not clear why such a fortunate turn occurred in Japan, but similar situations have not occurred in other East Asian countries (such as South Korea), where the population is genetically close to Japan. Inoue said that virus mutations similar to those marked by scientists have been found in at least 24 countries. He and his team plan to publish a paper by the end of November detailing their findings.
Even if the theory of natural extinction is confirmed, it is at best a temporary probation for the Japanese. Inoue believes that although quarantine measures and immigration controls may delay the emergence of new varieties in Japan, new and more successful strains may eventually enter the country.
At the same time, Tokyo is preparing for the new wave of Covid-19 this winter and is preparing to coexist with the virus. According to reports, the government plans to relax travel restrictions by increasing the number of people allowed to enter the country every day from 3,500 to 5,000.
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