key: cord-0903652-ic1kyn3z authors: Shimura, Takako; Kosaki, Kenjiro title: Global spread of a Japan-originated Delta lineage of SARS-CoV-2 after the Tokyo Olympics is most likely unrelated to the Olympics date: 2022-02-08 journal: J Travel Med DOI: 10.1093/jtm/taac017 sha: aac0f038de5dcf26284c9b0b9c0ab54c34739737 doc_id: 903652 cord_uid: ic1kyn3z Participants of the 2021 Summer Olympics in Tokyo were required to adhere to strict health protocols, and there were no major local outbreaks within the separation bubbles. However, based on viral genomic data, we report that the Japan-specific Delta variants did spread out globally during or after the Olympics. U N C O R R E C T E D M A N U S C R I P T 2 Participants of the 2021 Summer Olympics in Tokyo were required to adhere to strict health protocols, and there were no major local outbreaks within the separation bubbles. However, based on viral genomic data, we report that the Japan-specific Delta variants did spread out globally during or after the Olympics. Under a state of public health emergency and international concern about the COVID-19 pandemic, the Olympic Games were held in Tokyo and other Japanese cities We conducted a phylodynamic analysis of SARS-CoV-2 genome sequences deposited in the international SARS-CoV-2 genome database, GISAID. 1 Sequences obtained from Japan and elsewhere were compared (Supplementary Table) ; we used the Nextstrain pipeline suite for sequence alignments, phylogenetic inferences, temporal dating of ancestral nodes, discrete trait geographic reconstructions, as well as inference However, our finding that the Japan-originated strain AY.29 was transmitted outbound multiple times has significant implications for forthcoming international mass gatherings, including the Beijing Winter Olympics. 5 As WHO states 6 , the epidemiological context, including the prevalence of variants of concern and their transmissibility (e.g., the Omicron variant), as well as the contact tracing and testing capacity 7 , need to be considered. Moreover, "fragile and vulnerable" countries may require extra support to avoid importing viral strains through international mass gatherings. This work was supported by the Japan Agency for Medical Research and Development provided under grant numbers [JP20fk0108536]. Takako Shimura conceived the study, analyzed and interpreted data, and wrote the manuscript of the study. Kenjiro Kosaki conceived the idea of the study and drafted it. International Olympic committee, international paralympic committee. Tokyo 2020 Playbooks. Available at: https://olympics.com/ioc/tokyo-2020-playbooks. (28 January 2022, date last accessed). Global initiative on sharing all influenza datafrom vision to reality Nextstrain: real-time tracking of pathogen evolution Multiple introductions of SARS-CoV-2 214 lineages from mainland Japan preceded the third wave of the COVID-19 epidemic in Hokkaido A dynamic nomenclature proposal for SARS-CoV-2 lineages to assist genomic epidemiology Mass gatherings medicine: public health issues arising from mass gathering religious and sporting events Key planning recommendations for mass gatherings in the context of COVID-19. © World Health Organization 2021 We downloaded the full nucleotide sequences of the SARS-CoV-2 genomes from the GISAID database (https://www.gisaid.org/). Sequence data were obtained from GISAID and tables listing all accession numbers of the sequences and contributors are available as supplementary information.