Identifying High-Risk Events for COVID-19 Transmission: Estimating the Risk of Clustering Using Nationwide Data

Viruses. 2023 Feb 6;15(2):456. doi: 10.3390/v15020456.

Abstract

The transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is known to be overdispersed, meaning that only a fraction of infected cases contributes to super-spreading. While cluster interventions are an effective measure for controlling pandemics due to the viruses' overdispersed nature, a quantitative assessment of the risk of clustering has yet to be sufficiently presented. Using systematically collected cluster surveillance data for coronavirus disease 2019 (COVID-19) from June 2020 to June 2021 in Japan, we estimated the activity-dependent risk of clustering in 23 establishment types. The analysis indicated that elderly care facilities, welfare facilities for people with disabilities, and hospitals had the highest risk of clustering, with 4.65 (95% confidence interval [CI]: 4.43-4.87), 2.99 (2.59-3.46), and 2.00 (1.88-2.12) cluster reports per million event users, respectively. Risks in educational settings were higher overall among older age groups, potentially being affected by activities with close and uncontrollable contact during extracurricular hours. In dining settings, drinking and singing increased the risk by 10- to 70-fold compared with regular eating settings. The comprehensive analysis of the COVID-19 cluster records provides an additional scientific basis for the design of customized interventions.

Keywords: contact tracing; disease outbreak; epidemiology; observational study; risk assessment; severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • COVID-19* / epidemiology
  • Cluster Analysis
  • Hospitals
  • Humans
  • Japan / epidemiology
  • SARS-CoV-2

Grants and funding

K.H. received funding from the Japan Society for the Promotion of Science (JSPS) KAKENHI (20K18953) and The Health Care Science Institute (IKEN). H.N. received funding from a Health and Labor Sciences Research Grant (20CA2024, 20HA2007, 21HB1002, and 21HA2016), the Japan Agency for Medical Research and Development (AMED; JP20fk0108140, JP20fk0108535, and JP21fk0108612), the Japan Society for the Promotion of Science (JSPS) KAKENHI (21H03198 and 22K19670), an Environment Research and Technology Development Fund (JPMEERF20S11804) of the Environmental Restoration and Conservation Agency of Japan, Kao Health Science Research, the Daikin GAP fund program of Kyoto University, Collaboration Grant from LEBER, and the Japan Science and Technology Agency (JST) SICORP program (JPMJSC20U3 and JPMJSC2105) and the RISTEX program for Science of Science, Technology and Innovation Policy (JPMJRS22B4). We thank local governments, public health centers, and institutes for surveillance, laboratory testing, epidemiological investigations, and data collection. The funders of the study had no role in the study design, data collection, data analysis, data interpretation, writing of the report, or the decision to submit the paper for publication.