Epidemiology of coronavirus disease 2019 in Yamagata Prefecture, Japan, January–May 2020: The importance of retrospective contact tracing

Junji Seto; Yoko Aoki; Kenichi Komabayashi; Yoko Ikeda; Mika Sampei; Naomi Ogawa; Yumiko Uchiumi; Shunji Fujii; Masami Chiba; Emiko Suzuki; Tatsuya Takahashi; Keiko Yamada; Yoshiko Otani; Yoshihiro Ashino; Kyoko Araki; Takeo Kato; Hitoshi Ishikawa; Tatsuya Ikeda; Hideaki Abe; Tadayuki Ahiko; Katsumi Mizuta

doi:10.7883/yoken.JJID.2020.1073

This article has now been updated. Please use the final version.

Epidemiology of coronavirus disease 2019 in Yamagata Prefecture, Japan, January–May 2020: The importance of retrospective contact tracing

Junji Seto, Yoko Aoki, Kenichi Komabayashi, Yoko Ikeda, Mika Sampei, Naomi Ogawa, Yumiko Uchiumi, Shunji Fujii, Masami Chiba, Emiko Suzuki, Tatsuya Takahashi, Keiko Yamada, Yoshiko Otani, Yoshihiro Ashino, Kyoko Araki, Takeo Kato, Hitoshi Ishikawa, Tatsuya Ikeda, Hideaki Abe, Tadayuki Ahiko, Katsumi Mizuta

Author information

Junji Seto
Yamagata Prefectural Institute of Public Health, Japan
Yoko Aoki
Yamagata Prefectural Institute of Public Health, Japan
Kenichi Komabayashi
Yamagata Prefectural Institute of Public Health, Japan
Yoko Ikeda
Yamagata Prefectural Institute of Public Health, Japan
Mika Sampei
Yamagata Prefectural Institute of Public Health, Japan
Naomi Ogawa
Yamagata Prefectural Institute of Public Health, Japan
Yumiko Uchiumi
Murayama Public Health Center, Japan
Shunji Fujii
Murayama Public Health Center, Japan
Masami Chiba
Mogami Public Health Center, Japan
Emiko Suzuki
Mogami Public Health Center, Japan
Tatsuya Takahashi
Okitama Public Health Center, Japan
Keiko Yamada
Okitama Public Health Center, Japan
Yoshiko Otani
Shonai Public Health Center, Japan
Yoshihiro Ashino
Shonai Public Health Center, Japan
Kyoko Araki
Yamagata City Institute of Public Health, Japan
Takeo Kato
Yamagata City Institute of Public Health, Japan
Hitoshi Ishikawa
Shonai Public Health Center, Japan
Department of Physical Therapy, Yamagata Prefectural University of Health Sciences, Japan
Tatsuya Ikeda
Yamagata Prefectural Institute of Public Health, Japan
Yamagata Prefecture Division of Health and Welfare Planning, Japan
Hideaki Abe
Yamagata Prefecture Division of Health and Welfare Planning, Japan
Tadayuki Ahiko
Yamagata Prefectural Institute of Public Health, Japan
Yamagata Prefecture Division of Health and Welfare Planning, Japan
Katsumi Mizuta
Yamagata Prefectural Institute of Public Health, Japan

Keywords: close contact, cluster-based approach, infection source, SARS-CoV-2, testing

JOURNAL FREE ACCESS Advance online publication

Article ID: JJID.2020.1073

DOI https://doi.org/10.7883/yoken.JJID.2020.1073

The final version of this article is now available: Vol. 74 (2021), No. 6 pp. 522-529

Details

Abstract

Public health interventions have served an important role in controlling coronavirus disease 2019 (COVID-19), a rapidly spreading infectious disease. To contribute to future COVID-19 countermeasures, we aimed at verifying the results of countermeasures achieved by public health centers (PHCs) against the first wave of COVID-19 in Yamagata Prefecture, Japan. During January–May 2020, 1,253 patients suspected of SARS-CoV-2 infection were invited for testing. Simultaneously, based on retrospective contact tracings, PHCs investigated the infection sources and transmission routes of laboratory-confirmed COVID-19 cases and tested 928 contacts. Consequently, 69 cases were confirmed during March 31 – May 4, 58 (84.1%; 95% confidence interval 75.5–92.7) of whom were found from contacts. The spread of infection was triggered by cases harboring epidemiological links outside of Yamagata. Then, the number of cases increased rapidly. However, PHCs identified epidemiological links in 61 (88.4%; 95% confidence interval 80.8–96.0) of the 69 cases and transmission chains up to the fifth generation. Finally, the spread of infection ended after approximately one month. Our results indicate that the identification of infection sources and active case finding from contacts based on retrospective contact tracing was likely to be an effective strategy to end the first wave of COVID-19 in Yamagata.

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