ABSTRACT
In the present study, we report a new sub-lineage of the SARS-CoV-2 Delta variant called AY.29, which has C5239T and T5514C mutations. We investigated the monthly trend of AY.29 in Japan within 37,737 Delta variants downloaded on October 2, 2021. Among the total Japanese Delta variants, the AY.29 sub-lineage accounted for 95.1%. In terms of monthly trends, the sequences became predominant in June, and accounted for 95.4%, 97.6% and 90.5% of the reported sequences in July, August and September, respectively. Furthermore, the number of Delta variants imported from abroad during the Tokyo 2020 Olympics and Paralympics (held in August 2021) was extremely low during the fifth wave in Japan. Therefore, the epidemic of the new Delta variant is attributable to a newly occurring mutation in Japan.
