COVID-19 Outbreak and Epidemiological Research in Japan - Part 2-

Abstract

After the Public Health Emergency of International Concern (PHEIC) was announced by WHO on 30 January, the number of daily cases in Japan continued to increase and reached over 150 on 24 February. On 25 February, The Cluster Management Task Force (CMTF) was established under the Novel Coronavirus Expert Meeting of the Ministry of Health, Labor and Welfare. Their mission was to 1) identify contacted persons by interviewing infected patients, 2) find infection cluster events, 3) identify risk factors causing cluster events, 4) announcing these factors to reduce cluster events. Professor Hiroshi Nishiura, an expert of theoretical epidemiology in Japan, took the lead in CMTF and provided evidence of strong heterogeneity of the number of secondary infections from a person infected with SARS-CoV2. This evidence supported the strategy of CMTF; suppressing epidemic by reducing the number of cluster events but not by drastic countermeasures such as city lockdown. In addition, CMTF found out that the three primary factors are the risk of causing cluster events. The three factors are closed spaces, crowded places, and close-contact settings, and thereafter, called “Three Cs” and announced as a slogan to change people’s activity.