Familial Clusters of Coronavirus Disease in 10 Prefectures, Japan, February−May 2020

Abstract

A s of May 31, 2020, Japan had reported >16,800 confirmed coronavirus disease (COVID-19) cases and 890 related deaths. The cluster-based approach is one of the pillars of control measures in Japan (1). Sixty-one clusters were documented in healthcare facilities, restaurants, workplaces, and music venues during January-April 2020 (2). However, the transmission within households, one of the highest-risk settings, has not been fully investigated.