key: cord-0775618-o4j8rw9k
authors: Eguchi, Akifumi; Yoneoka, Daisuke; Shi, Shoi; Tanoue, Yuta; Kawashima, Takayuki; Nomura, Shuhei; Matsuura, Kentaro; Makiyama, Koji; Ejima, Keisuke; Gilmour, Stuart; Nishiura, Hiroshi; Miyata, Hiroaki
title: Trend change of transmission route of COVID-19-related symptoms in Japan
date: 2020-08-28
journal: Public Health
DOI: 10.1016/j.puhe.2020.08.020
sha: bc6a59a68bcbfa98521af768123cbc1b8c2c6fb0
doc_id: 775618
cord_uid: o4j8rw9k

Objectives The Japanese prime minister declared a state of emergency on April 7 to combat the outbreak of coronavirus disease 2019 (COVID-19). This declaration was unique in the sense that it was essentially driven by the voluntary restraint of the residents. We examined the change of infection route by investigating contact experiences with COVID-19-positive cases. Study design This study is a population-level questionnaire-based study using a social networking service (SNS). Methods To assess the impact of the declaration, this study used population-level questionnaire data collected from an SNS with 121,375 respondents (between March 27 and May 5) to assess the change in transmission routes over the study period, which was measured by investigating the association between COVID-19-related symptoms and (self-reported) contact with COVID-19-infected individuals. Results The results of this study show that the declaration prevented infections in the workplace, but increased domestic infections as people stayed at home. However, after April 24, workplace infections started to increase again, driven by the increase in community-acquired infections. Conclusions While careful interpretation is necessary because our data is self-reported from voluntary SNS users, these findings indicate the impact of the declaration on the change in transmission routes of COVID-19 over time in Japan.

The World Health Organization (WHO) officially declared the outbreak of coronavirus disease 2019 32 to be a pandemic on March 11, 2020. Since the first deaths were reported in early 3,595,662 cases and 247,652 deaths reported worldwide [2, 3] . In response, the Japanese prime 35 minister, Shinzo Abe, declared a state of emergency in 7 of the 47 prefectures on the evening of 36 April 7 [4] , and this was extended to become nationwide on April 16 [5] due to a gradual increase 37 in polymerase chain reaction (PCR)-positive COVID-19 cases with an untraceable pathway of 38 infection. The declaration had limited legally enforceable measures, which is different from the so-39 called 'lockdowns' (e.g. city blockades with penalties) that have been in place in the US, the UK, 40 France, Germany, Italy and India, and it is essentially driven by the voluntary restraint of the 41 residents in Japan [4] . In this sense, Japan has a unique Japanese-style lockdown policy based on 42 the voluntary efforts of residents to weaken the spread of the infection, with no penalties for going 43 out or commercial activities.

In infectious disease control, capturing the real-time epidemiological situation is a key factor to 46 control the spread of the infection. To address this issue, COOPERA (COvid-19: Operation for Personalized Empowerment to Render smart prevention And care seeking), a new health care 48 monitoring system, has recently been launched in a collaboration with the Kanagawa prefectural 49 government and LINE Corporation as a way to monitor the spread of COVID-19 and associated 50 societal factors [6] . LINE provides Japan's largest mobile messenger application with 83 million 51 monthly active users (covering 65% of Japan's total population). COOPERA asks participants about 52 their individual information, including medical and psychiatric conditions, and contact experiences 53 with other individuals. In response to the given information, COOPERA provides personalised 54 assistance, such as telephone consultation for participants who report serious symptoms [7] . Data 55 collected by COOPERA have been used to monitor the real-time situation of COVID-19 and its 56 usefulness for medical decision making has already been shown [8] [9] [10] .

In this study, we focus on the change of association between COVID-19-related symptoms and 59 (self-reported) contact experience with COVID-19-positive cases over time, including before and 60 after the state of emergency. In particular, we investigate the time trend of (1) domestic infections 61 (i.e., within-household infection) and (2) community-acquired infections with an unknown route of 62 transmission. In addition, by examining the impact of the voluntary Japanese-style lockdown policy, 63 this study provides a useful insight not only for Japan but also for other countries that are 64 preparing to relax their lockdowns in the near future.

age, gender, occupation, medical history, preventive actions and postcode, and (2) health 68 conditions, including current and past month's symptoms (presence or absence of fever, strong 69 feeling of weariness or shortness of breath) and duration of these symptoms. In particular, we 70 focused on fever in this study. Participants with any COVID-19-related symptoms were asked 71 additional questions about their contact experiences with COVID-19-infected individuals, and, if 72 yes, they were asked about their relationships with these individuals (e.g. if they were colleagues, 73 classmates or family members). Participants with any COVID-19-related symptoms were followed-74 up daily and those without any symptoms were followed-up once every 4 days. Figure S1 in the supplementary material). Therefore, it 144 should be noted that the proportion may not be stable on some days due to a small number of 145 respondents. Third, the difference in available information about the symptoms of family members 146 and those of colleagues and classmates might be a source of bias (e.g. information on family 147 members was easy to obtain, but that of classmates and colleagues was relatively difficult). Other 148 limitations are discussed extensively elsewhere [10, 14] .

In conclusion, given that Japan has a unique and weak lockdown policy with limited legally 151 enforceable measures, the results of this study provide a useful insight for preparing for second or 

The New York Times. China Reports First Death From New Virus

World Health Organization. Coronavirus disease (COVID-19) Pandemic

Johns Hopkins Coronavirus Resource Center. Coronavirus COVID-19 Global Cases by the 203 Center for Systems Science and Engineering

Cabinet Secretariat. Press Conference by the Prime Minister Regarding the Declaration of a 206 State of Emergency

Kanagawa prefecture. Personal support for COVID-19 using LINE

The relationship between fever rate and telework implementation as 216 a social distancing measure against the COVID-19 pandemic in Japan

Mental health of family, friends, and co-workers of COVID-19 patients in 218

Early SNS-based screening system for the COVID-19 in Japan: a 220 population-level observational study

We would like to thank Tokyo, Kanagawa, Saitama prefectures and other prefectures for installing 169 the COOPERA system and providing us with data, LINE Corporation for developing and maintaining 170 the system, and Amazon Web Services, Inc. for providing the data storage space. We are also