Wagatsuma Keita, Phyu Wint Wint, Osada Hidekazu, Tang Julian W, Saito Reiko
Division of International Health (Public Health) , Graduate School of Medical and Dental Sciences, Niigata University, Japan.
Infectious Diseases Research Center of Niigata University in Myanmar, Graduate School of Medical and Dental Sciences, Niigata University, Japan.
Jpn J Infect Dis. 2021 Mar 24;74(2):157-160. doi: 10.7883/yoken.JJID.2020.471. Epub 2020 Aug 31.
Since the coronavirus disease 2019 (COVID-19) emerged in Wuhan, China, in December 2019, it has rapidly spread worldwide, and the number of cases is also increasing in Japan. The number of COVID-19 cases in Japan in the early stages was not uniform, and cases were largely concentrated in several prefectures. There was a strong, positive correlation between the distribution of COVID-19 cases and the number of foreign travelers as well as Chinese travelers, at prefectural level, with coefficients of 0.68 (P < 0.0001) and 0.60 (P < 0.0001), respectively. Moreover, phylogenetic tree analysis revealed that all the registered SARS-CoV-2 detected from January 23 to February 29, 2020, belonged to Chinese lineage, while those detected in March 2020 belonged to American and European lineages. Only 14 (20.3%) were infected outside Japan; however, the majority of the cases (79.7%) were infected domestically. In conclusion, a higher number of COVID-19 cases were identified in prefectures with more Chinese travelers, supporting the importance of enforcing policies that restrict the entry of overseas travelers to control COVID-19 spread. These findings highlight the risk of secondary transmission in the community caused by apparent or silently imported cases.
自2019年12月中国武汉出现新型冠状病毒肺炎（COVID-19）以来，它已在全球迅速传播，日本的病例数也在增加。日本早期的COVID-19病例数并不均匀，病例主要集中在几个县。在县级层面，COVID-19病例分布与外国旅行者以及中国旅行者数量之间存在很强的正相关，系数分别为0.68（P < 0.0001）和0.60（P < 0.0001）。此外，系统发育树分析显示，2020年1月23日至2月29日检测到的所有登记的严重急性呼吸综合征冠状病毒2（SARS-CoV-2）均属于中国谱系，而2020年3月检测到的属于美国和欧洲谱系。仅14例（20.3%）在日本境外感染；然而，大多数病例（79.7%）是在国内感染的。总之，中国旅行者较多的县确诊的COVID-19病例数较多，这支持了实施限制海外旅行者入境政策以控制COVID-19传播的重要性。这些发现凸显了明显或隐性输入病例在社区中引起二次传播的风险。
