Despite having a vaccination rate comparable to that of many other countries, Japan saw an unprecedented drop in the number of Covid-19 cases.Japan was in the midst of the fifth and largest Covid-19 wave since the pandemic began in August.
It even recorded over 20,000 cases per day.The Delta variant, due to its high transmissibility, ended up replacing other mutations in Sars-CoV-2 and becoming the predominant strain of the virus in several countries.
However, the number of cases has decreased significantly since then, and today, while several countries with similar vaccination rates are dealing with a new wave of infections, Japan registers just over 100 new infections per day (data from 11/23).Since the country’s last state of emergency ended in early October, trains, cafes, and restaurants have been consistently packed – despite the population’s continued use of social distancing and masks.Photographer: Getty ImagesApproximately 75% of the country’s population has been immunised, according to the photo caption.
The hypothesis of’self-extinction’According to some researchers, the decrease in the number of cases could be explained by Delta’s “self-destruct” movement during its evolutionary development in the Japanese population.
The hypothesis was proposed in light of the growing disparities between the characteristics of the pandemic in Japan, where 75 percent of the population was immunised, and other countries with a comparable level of immunisation.Spain, for example, which has one-third the population of the Asian country and where 80 percent of residents have already been immunised, is still struggling to flatten the infection curve, with nearly 7,000 new cases reported on the 23rd.
“In Japan, the Delta variant was highly contagious and gradually replaced other strains.” However, as the mutations accumulated, we believe the virus became defective, unable to replicate,” said geneticist Ituro Inoue of Japan’s National Institute of Genetics to The Japan Times.”Given that cases have not increased, we believe that the virus was on its way to natural extinction at some point during these mutations,” the scientist added.
Photographer: Getty Imagescaption for a photograph,Restaurants were once again full as the number of cases decreased.natural procedureSince the start of the pandemic, different variants of Sars-CoV-2 have been disappearing.”Viruses that infect animals and humans do this all the time.” “Recall that the Alpha, Beta, and Gamma variants were mostly replaced by Delta variants,” says virologist Julian Tang of the University of Leicester, UK, to BBC Mundo, the BBC’s Spanish language service.
“It’s all about viral fitness” (ability of the virus to replicate in a given environment). Perhaps something about the Japanese people’s immunity has changed the way the virus behaves there. Time will tell if it happens in other countries as well,” Tang concludes.APOBEC3A, a defence enzyme that attacks different viruses – including the coronavirus that causes Covid-19 – has already been found to be more prevalent in Asian populations than in populations in other regions such as Africa and Europe.
This enzyme was studied by researchers from the National Institute of Genetics and Niigata University to see if it could inhibit coronavirus activity.The researchers compared genetic diversity data for Delta and Alpha variants in samples collected in Japan between June and July and discovered that the development of new mutations seemed to stop abruptly, resulting in genetic alterations that prevented the virus from replicating.
“They discovered mutations in the nsp14 protein, which is involved in repairing replication defects.” If this protein has more mutations than usual, it can be inactivated or become inefficient, causing the pathogen to collapse,” explains José Manuel Bautista, professor of biochemistry and molecular biology at Spain’s Complutense University.
While Bautista believes the sharp drop in cases is also due to factors such as mass vaccinations and distancing measures, he admits that the downward trajectory on the contagion curve is impressive.”It is normal for it to decrease gradually because those infected are usually diagnosed days later” (from the start of the infection). “However, the drop in cases (in Japan) is dramatic, indicating that the theory of self-destruction is plausible,” he noted.
Despite the positive outlook, scientists are cautious and avoid making predictions about what might happen in the future. The pandemic is constantly evolving, demonstrating that, despite vaccination and containment efforts, the world is not completely free of new outbreaks.
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