COVID-19 case-clusters and transmission chains in the communities in Japan

Furuse, Yuki; Tsuchiya, Naho; Miyahara, Reiko; Yasuda, Ikkoh; Sando, Eiichiro; Ko, Yura K.; Imamura, Takeaki; Morimoto, Konosuke; Imamura, Tadatsugu; Shobugawa, Yugo; Nagata, Shohei; Tokumoto, A.; Jindai, Kazuaki; Suzuki, Motoi; Oshitani, Hitoshi

doi:10.1016/j.jinf.2021.08.016

Cited by 14 publications

(14 citation statements)

References 8 publications

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“…There were more transmissions to the elderly from younger age groups as well as elderly-to-elderly transmission in the later phases of each wave. This is consistent with a previous study that reported community cluster outbreaks among the elderly in Japan (Furuse et al, 2021). Since the most severe cases occur in the elderly (Driscoll et al, 2021), interventions focusing on preventing infection in older age groups are essential to minimize the impact of COVID-19.…”

Section: Discussionsupporting

confidence: 92%

Secondary transmission of SARS-CoV-2 during the first two waves in Japan: Demographic characteristics and overdispersion

Furuse

Ninomiya

et al. 2022

International Journal of Infectious Diseases

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Section: Discussionsupporting

confidence: 92%

Secondary transmission of SARS-CoV-2 during the first two waves in Japan: Demographic characteristics and overdispersion

Furuse

Ninomiya

et al. 2022

International Journal of Infectious Diseases

Self Cite

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“…Indeed, we were unable to fully assess the heterogeneity of transmission dynamics in specific regions associated with alternative indicators of each NPI because the present study covers the whole of Japan rather than each prefecture. Indeed, the epidemiological effects of NPIs on the transmission dynamics of seasonal influenza may have different probability distributions, as it is necessary to consider the increase in local clusters of COVID-19 in remote prefectures of Japan [ 76 , 77 , 78 , 79 ]. Additionally, compared to severe measures, such as city closures (i.e., lockdown), implemented in other countries, the legal enforcement of the state of emergency declaration in Japan is moderate, and the government relies on people’s voluntary action and the resulting peer pressure to reduce contact at the community level [ 80 ].…”

Section: Discussionmentioning

confidence: 99%

Was the Reduction in Seasonal Influenza Transmission during 2020 Attributable to Non-Pharmaceutical Interventions to Contain Coronavirus Disease 2019 (COVID-19) in Japan?

Wagatsuma

Koolhof

Saito

2022

Viruses

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We quantified the effects of adherence to various non-pharmaceutical interventions (NPIs) on the seasonal influenza epidemic dynamics in Japan during 2020. The total monthly number of seasonal influenza cases per sentinel site (seasonal influenza activity) reported to the National Epidemiological Surveillance of Infectious Diseases and alternative NPI indicators (retail sales of hand hygiene products and number of airline passenger arrivals) from 2014–2020 were collected. The average number of monthly seasonal influenza cases in 2020 had decreased by approximately 66.0% (p < 0.001) compared to those in the preceding six years. An increase in retail sales of hand hygiene products of ¥1 billion over a 3-month period led to a 15.5% (95% confidence interval [CI]: 10.9–20.0%; p < 0.001) reduction in seasonal influenza activity. An increase in the average of one million domestic and international airline passenger arrivals had a significant association with seasonal influenza activity by 11.6% at lag 0–2 months (95% CI: 6.70–16.5%; p < 0.001) and 30.9% at lag 0–2 months (95% CI: 20.9–40.9%; p < 0.001). NPI adherence was associated with decreased seasonal influenza activity during the COVID-19 pandemic in Japan, which has crucial implications for planning public health interventions to minimize the health consequences of adverse seasonal influenza epidemics.

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“…In the first and second waves, retrospective contact-tracing investigations revealed the source patients and clusters of more than 60% of confirmed cases. After a certain period, especially with the rapid growth of daily cases, the outbreaks in hospitals, healthcare facilities, and schools, posed significant challenges to large-scale case investigation and contract tracing [ 39 ] with inadequate human resources. The number of reported cases without an identified epidemiological link and unrecognized community transmission chains increased [ 40 ].…”

Section: Discussionmentioning

confidence: 99%

Exploring spatiotemporal patterns of COVID-19 infection in Nagasaki Prefecture in Japan using prospective space-time scan statistics from April 2020 to April 2022

Cai

et al. 2022

Arch Public Health

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Background Up to April 2022, there were six waves of infection of coronavirus disease 2019 (COVID-19) in Japan. As the outbreaks continue to grow, it is critical to detect COVID-19’s clusters to allocate health resources and improve decision-making substantially. This study aimed to identify active clusters of COVID-19 in Nagasaki Prefecture and form the spatiotemporal pattern of high-risk areas in different infection periods. Methods We used the prospective space-time scan statistic to detect emerging COVID-19 clusters and examine the relative risk in five consecutive periods from April 1, 2020 to April 7, 2022, in Nagasaki Prefecture. Results The densely inhabited districts (DIDs) in Nagasaki City have remained the most affected areas since December 2020. Most of the confirmed cases in the early period of each wave had a history of travelling to other prefectures. Community-level transmissions are suggested by the quick expansion of spatial clusters from urban areas to rural areas and remote islands. Moreover, outbreaks in welfare facilities and schools may lead to an emerging cluster in Nagasaki Prefecture’s rural areas. Conclusions This study gives an overall analysis of the transmission dynamics of the COVID-19 pandemic in Nagasaki Prefecture, based on the number of machi-level daily cases. Furthermore, the findings in different waves can serve as references for subsequent pandemic prevention and control. This method helps the health authorities track and investigate outbreaks of COVID-19 that are specific to these environments, especially in rural areas where healthcare resources are scarce.

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COVID-19 case-clusters and transmission chains in the communities in Japan

Cited by 14 publications

References 8 publications

Secondary transmission of SARS-CoV-2 during the first two waves in Japan: Demographic characteristics and overdispersion

Secondary transmission of SARS-CoV-2 during the first two waves in Japan: Demographic characteristics and overdispersion

Was the Reduction in Seasonal Influenza Transmission during 2020 Attributable to Non-Pharmaceutical Interventions to Contain Coronavirus Disease 2019 (COVID-19) in Japan?

Exploring spatiotemporal patterns of COVID-19 infection in Nagasaki Prefecture in Japan using prospective space-time scan statistics from April 2020 to April 2022

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