2021年12月至2022年1月，日本大阪，在新冠病毒奥密克戎毒株传播早期加强病例发现和自我隔离措施。
Enhanced case finding and self-isolation measures in the early phase of SARS-CoV-2 Omicron transmission, Osaka, Japan, December 2021-January 2022.
作者信息
Kobayashi Miho, Kakimoto Kensaku, Yahata Yuichiro, Kobayashi Yusuke, Nagai Hitomi, Tanikake Chisato, Fukumura Kazumi, Date Keiko, Murata Hiromi, Kitagawa Sae, Yoshida Yuki, Kamoda Yui, Akazaki Miho, Tanabe Masaaki, Shirai Chika, Shimada Tomoe, Kamigaki Taro, Sekizuka Tsuyoshi, Kuroda Makoto, Sunagawa Tomimasa
机构信息
Field Epidemiology Training Program, National Institute of Infectious Diseases, Tokyo, Japan.
Gunma Prefectural Institute of Public Health and Environmental Sciences, Gunma, Japan.
出版信息
Western Pac Surveill Response J. 2025 Apr 14;16(2):1-10. doi: 10.5365/wpsar.2025.16.2.1129. eCollection 2025 Apr-Jun.
OBJECTIVE
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant B.1.1.529 (Omicron) was first detected in Japan in November 2021. In Osaka, public health centres subsequently increased active case finding and encouraged self-isolation. This study investigated the effectiveness of these countermeasures.
METHODS
Cases targeted for analysis were persons who had neither recently travelled abroad nor had contact with foreign tourists but tested positive for SARS-CoV-2 between 24 November 2021 and 4 January 2022 and were suspected or confirmed to have the Omicron variant. We performed a descriptive analysis and calculated the reproduction number () for each generation using the branching process method. Genomic sequencing data were analysed to plot a haplotype network.
RESULTS
A total of 251 cases were analysed. The median age was 30 years, and 46% (115/251) were in their 20s or younger. The first Omicron case in Osaka was detected on 21 December 2021. Local public health centres conducted health monitoring and contact tracing. We analysed , using information from six clusters, including 42 pairs with a clear relationship between the case and the infected contact (infector-infectee pairs); the clusters had 19, 21 and 2 cases in each subsequent generation. The basic ( = 0) was estimated to be 3.2, and subsequent generations ( = 1, 2) of decreased to 1.1 and 0.1, respectively. The haplotype network showed that these cases constituted a monophyletic group with others detected around Osaka, indicating that these case-related clusters had been contained and were not involved in the nationwide Omicron waves.
DISCUSSION
Active case finding and self-isolation were found to be effective in limiting the spread of an emerging novel variant.
目的
严重急性呼吸综合征冠状病毒2（SARS-CoV-2）变种B.1.1.529（奥密克戎）于2021年11月在日本首次被检测到。在大阪，公共卫生中心随后加强了主动病例发现并鼓励自我隔离。本研究调查了这些应对措施的有效性。
方法
分析的病例为既非近期出国旅行也未接触外国游客，但在2021年11月24日至2022年1月4日期间SARS-CoV-2检测呈阳性且疑似或确诊感染奥密克戎变种的人员。我们进行了描述性分析，并使用分支过程方法计算每一代的再生数（(R)）。对基因组测序数据进行分析以绘制单倍型网络。
结果
共分析了251例病例。中位年龄为30岁，46%（115/251）为20岁及以下。大阪的首例奥密克戎病例于2021年12月21日被检测到。当地公共卫生中心进行了健康监测和接触者追踪。我们利用来自六个聚集性疫情的信息分析了(R)，其中包括42对病例与受感染接触者（感染者-被感染者对）之间关系明确的情况；这些聚集性疫情在随后各代分别有19例、21例和2例。基本再生数（(R_0)）估计为3.2，随后几代（(R_1)、(R_2)）分别降至1.1和0.1。单倍型网络显示，这些病例与大阪周边地区检测到的其他病例构成一个单系群，表明这些与病例相关的聚集性疫情已得到控制，未参与全国范围的奥密克戎疫情传播。
讨论
主动病例发现和自我隔离被发现对于限制新出现的变异毒株的传播是有效的。
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