Transmission of COVID-19 in Nightlife, Household, and Health Care Settings in Tokyo, Japan, in 2020

Abstract

ImportanceThere have been few studies on the heterogeneous interconnection of COVID-19 outbreaks occurring in different social settings using robust, surveillance epidemiological data.ObjectivesTo describe the characteristics of COVID-19 transmission within different social settings and to evaluate settings associated with onward transmission to other settings.Design, Setting, and ParticipantsThis is a case series study of laboratory-confirmed COVID-19 cases in Tokyo between January 23 and December 5, 2020, when vaccination was not yet implemented. Using epidemiological investigation data collected by public health centers, epidemiological links were identified and classified into 7 transmission settings: imported, nightlife, dining, workplace, household, health care, and other.Main Outcomes and MeasuresThe number of cases per setting and the likelihood of generating onward transmissions were compared between different transmission settings.ResultsOf the 44 054 confirmed COVID-19 cases in this study, 25 241 (57.3%) were among male patients, and the median (IQR) age of patients was 36 (26-52) years. Transmission settings were identified in 13 122 cases, including 6768 household, 2733 health care, and 1174 nightlife cases. More than 6600 transmission settings were detected, and nightlife (72 of 380 [18.9%]; P < .001) and health care (119 [36.2%]; P < .001) settings were more likely to involve 5 or more cases than dining, workplace, household, and other settings. Nightlife cases appeared in the earlier phase of the epidemic, while household and health care cases appeared later. After adjustment for transmission setting, sex, age group, presence of symptoms, and wave, household and health care cases were less likely to generate onward transmission compared with nightlife cases (household: adjusted odds ratio, 0.03; 95% CI, 0.02-0.05; health care: adjusted odds ratio, 0.57; 95% CI, 0.41-0.79). Household settings were associated with intergenerational transmission, while nonhousehold settings mainly comprised transmission between the same age group. Among 30 932 cases without identified transmission settings, cases with a history of visiting nightlife establishments were more likely to generate onward transmission to nonhousehold settings (adjusted odds ratio, 5.30 [95% CI, 4.64-6.05]; P < .001) than those without such history.Conclusions and RelevanceIn this case series study, COVID-19 cases identified in nightlife settings were associated with a higher likelihood of spreading COVID-19 than household and health care cases. Surveillance and interventions targeting nightlife settings should be prioritized to disrupt COVID-19 transmission, especially in the early stage of an epidemic.

Fukuchi-Manabe Score for Infection Control Measures During the Very Early COVID-19 Pandemic Period When Access to Reverse Transcription-Polymerase Chain Reaction Testing Was Poor in Japan: A Single-Center Observational Prospective Cohort Study

“…No nosocomial infection among healthcare providers was observed at our institution. In contrast, nosocomial infections were frequently observed during the same period in Japan [ 29 ]. We used not only this scoring method but also other infection control measures, such as education for staff and self-quarantine.…”

Population Behavior Changes Underlying Phasic Shifts of SARS-CoV-2 Exposure Settings Across 3 Omicron Epidemic Waves in Hong Kong: Prospective Cohort Study

“…With extensive facility closures at tier 1, the halting of community activities had likely further compelled SARS-CoV-2 transmissions within the residence [ 25 ]. Such an epidemiological transition was mirrored in the outbreak dynamics, in which the precipitous rise mimicked the multiple infections established in fully susceptible households, whereas the exponential decline resulted from the limited onward transmission preempted by isolation [ 10 ]. In hindsight, discouraging multihousehold gatherings could be an effective means to confine the epidemic spread when new infections surge in the community [ 26 ].…”

“…Thus, the nature of social contacts in different settings could also play an important role in affecting the level of virus exposure and infection risk. Based on contact-tracing data, the transmission dynamics of SARS-CoV-2 can also be observed to be largely variable among clusters of infection emerging from different environments [ 8 - 10 ]. Yet, evidence formally appraising the association between exposure and outbreaks in a broader community context remains scarce.…”

Revisiting Japan's early COVID‐19 countermeasures

“…Specifically, in a study in which some of the authors were members of the Japanese government's Subcommittee on Novel Coronavirus Disease Control, Imamura et al have reported that prioritizing surveillance and intervention in nightlife settings was effective in preventing the spread of COVID‐19, particularly in the early stages of the outbreak. 2 This conclusion was based on the surveillance of infection rates in Tokyo from January 23 to December 5, 2020, when vaccinations had not yet been administered. 2 However, during this investigation period, PCR testing was limited to those with severe symptoms, inevitably overlooking asymptomatic individuals or those with mild symptoms.…”

“… 2 This conclusion was based on the surveillance of infection rates in Tokyo from January 23 to December 5, 2020, when vaccinations had not yet been administered. 2 However, during this investigation period, PCR testing was limited to those with severe symptoms, inevitably overlooking asymptomatic individuals or those with mild symptoms. Consequently, relying on the reported data from Japan during this period may result in an underestimation of the number of infections.…”