"AY.29 Delta Variant Protects Us"… Japanese Professor Proposes Hypothesis for 'Sharp Decline in Cases'

A street in Shinjuku, Tokyo, Japan.
Photo by Yonhap News

[Asia Economy Reporter Na Ye-eun] A new hypothesis has been raised regarding the noticeable sharp decline in Japan's new COVID-19 cases, suggesting that a specific mutation has been added to a major virus strain in Japan.

According to major foreign media reports on the 9th (local time), Japan's daily number of confirmed cases is currently less than one per million people, with only 136 cases reported on the 8th based on NHK statistics, and no deaths reported on the 5th.

In contrast, South Korea, which has a similar vaccination rate, has seen cases rise to the 7,000 range, and countries like Singapore and Australia are still experiencing an increase in cases.

Professor Ituro Inoue of the National Institute of Genomics in Japan suggested the possibility that a specific mutation added to the dominant virus strain in Japan may have reduced its infectivity. He predicted, "The AY.29 type virus, a subtype of the Delta variant, is currently dominant in Japan, and this mutation may have caused another mutation that lowers infectivity."

Professor Ituro said, "I think AY.29 is protecting us from other mutations," but added that this is only a hypothesis and he is not 100% certain.

Professor Paul Griffin of the University of Queensland in Australia said that the sharp decline in Japan's cases is due to a combination of factors such as weather, population density, and epidemic response strategies. He advised, "We need to try to learn lessons from other countries, but since there are many variables, we should not assume that every country will have the same experience."

Foreign media also reported that even considering vaccines and mask-wearing, some view Japan's rapid decrease in cases as a matter of "timing."

Meanwhile, Japanese health authorities are imposing entry restrictions to prevent additional influxes of the Omicron variant. Booster shot vaccinations began last week, and after experiencing the worst "fifth wave" in August, hospital capacity has been increased by more than 30%.

This content was produced with the assistance of AI translation services.