Estimating effectiveness and its mechanism of case isolation

2021 Fiscal Year Final Research Report

• Project/Area Number: 17H04701
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Life / Health / Medical informatics
• Research Institution: Kyoto University (2020-2021); Hokkaido University (2017-2019)
• Principal Investigator: Nishiura Hiroshi 京都大学, 医学研究科, 教授 (70432987)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: 感染症情報 / 疫学 / 数理モデル / 危機管理 / 保健情報

Outline of Final Research Achievements

Nonpharmaceutical interventions including case isolation is widely applicable to various infectious diseases to which vaccine and treatment are under development. However, the protective effect of case isolation has not been quantitatively clarified. The present study employed a mathematical approach to quantifying the secondary transmission phenomena as a function fo time since infection in the primary case. Formulating novel models and analyzing empirical epidemiological data, we have explicitly estimated the effectiveness of case isolation. During the project, a pandemic of novel coronavirus disease (COVID-19) started and relevant studies on COVID-19 were also conducted. We have shown that the serial interval of COVID-19 was as short as 5 days, which was close to the value of the incubation period.

Free Research Field

感染症疫学

Academic Significance and Societal Importance of the Research Achievements

隔離効果の推定手法を定式化し、2014年のナイジェリアにおけるエボラ出血熱流行データから隔離が2次感染を約46％減少させたことを実証した。また、新型コロナウイルス感染症では発症間隔と潜伏期間の値がほぼ同じ程度であり、同感染症の2次感染の多く（実際には50％程度）が発病前に起こっていることを示した。本情報は、新型コロナウイルス感染症の流行対策においては単なる早期診断と隔離だけでは流行を制御することはかなり難しいことを意味するものであった。本研究によって接触者追跡に基づく対策が無益なものにならないように遡り調査が実施され、同論文は2022年6月1日時点までに合計1066回の引用を受けた。