Three months after the delta variable caused daily infections to be recorded in Japan, the graph of new corona cases has decreased.
Infection began to increase in mid-July. Then the curve declined rapidly, from more than 25,000 cases at worst by the end of August, to about 2,000 cases a month later.
Almost two months ago, the state of emergency was lifted in the country. Since November 1, they’ve had about 200 cases of infection per day, or fewer. On November 7, the country recorded its first day in more than a year without a coronavirus-related death.
The researchers point to several reasons, including high vaccination rates and measures such as social distancing and use of sanitary napkins, which are now deeply rooted in Japanese society, he writes. Japan Times.
However, there may be a startling theory regarding the genetic changes that occur with the virus during reproduction.
The fifth and largest wave of infections in Japan was driven by the delta variable. According to Ituro Inoue, a professor at the Japan Institute of Genetics, the country’s delta variant may have accumulated a lot of mutations in the virus’ error-correcting protein, called nsp14.
Simply explain; This may have resulted in the virus struggling to fix bugs in time, which could lead to “self-destruction”.
Studies have shown that more people in Asia than in Europe and Africa have a “defense enzyme” called APOBEC3A, which attacks RNA viruses — such as SARS-CoV-2 viruses, the Japan Times writes. So researchers at the Institute of Genetics and Niigata University wanted to know whether APOBEC3A affects the nsp14 protein and whether it can suppress the activity of the coronavirus.
– We were literally shocked by the results. The delta variant in Japan was highly convertible and kept the other variants out. But as mutations accumulate, we think it eventually became a defective virus that failed to make copies of itself. “Given that cases have not increased, we believe that at some point during such mutations, they went straight to natural extinction,” Inoue told the Japan Times.
The possibility that the SARS-CoV-2 variants circulating in Japan will mutate in a direction that limits the ability of the virus to spread is certainly present, Assistant Director of Health Espen Rostroup Nakstad told Dagbladet.
– In this case, this will be confirmed by sequencing the genome of the virus in the future as the spread pattern of the different delta variants in the country can be followed more accurately.
He also points out that Japan’s relatively high vaccine coverage, and strict local infection control measures and high compliance with them, may explain why the R-number is below one in Japan, while it is higher than one in most of Europe.
– Both cases may contribute to the reduction in infection in Japan. In this case, there are important questions that I think we will soon have better answers to.
Nakstad points out that there are many reasons why SARS-CoV-2 spreads at different speeds and affects differently on different continents.
– In some Asian countries, the spread of the virus is also affected by a high level of action over time with very good compliance with infection control boards, for example in Japan. Therefore, there are many reasons why the epidemic has different footprints in different parts of the world.
Nakstad also says that it is difficult to compare numbers for the prevalence of different virus variants, because PCR testing and virus genome sequencing are performed on a small scale in many developing countries.
Of course, other conditions of the virus and the human immune response can play a role.
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