Nightlife Setting Found to Propel the Spread of COVID-19

Nightlife caused a significant number of large outbreaks of COVID-19 infection, according to a study from Tokyo, Japan, published in JAMA Network Open. Although households were a primary transmitter of COVID-19 to non-household settings, they did not initiate as many large outbreaks.

“These findings suggest (1) that nightlife settings are associated with an increased likelihood of spreading COVID-19 and (2) that although household and health care settings affect populations with an increased risk of death, they are less likely to generate onward transmission,” the study authors wrote in the article.

Prior research indicates that younger populations have a higher risk for generating large COVID-19 outbreaks (5 or more offspring cases), and were more likely to sustain this transmission. However, the relationship between patterns of onward transmission—or transmission from one setting to another—and the risk of large outbreak was lacking.

Investigators analyzed 44,054 laboratory-confirmed COVID-19 cases prior to vaccine availability between January 23 and December 5, 2020, to understand how different settings in Tokyo enabled the spread of COVID-19. They also studied transmission setting characteristics and how these could be attributed to COVID-19 transmission in the community.

Specifically, the investigators evaluated the relationship between times of infection and transmission settings, number of cases involved at each setting, the factors associated with transmission beyond the original setting, and data from detailed epidemiological investigations. Transmission settings included imported, nightlife, dining, workplace, household, health care, and other.

Adjusting for setting, sex, age, group, symptoms, and epidemic wave—wave 1 was January 14 to May 25, 2020; wave 2 from May 26 to September 30, 2020; wave 3 was October 1 to December 6, 2020—the data showed that the nightlife setting was associated with higher rates of offspring cases and onward transmission compared to those from the health care setting.

Nightlife settings can have “crowded places, inadequate ventilation, on-site eating and drinking with frequent alcohol consumption, and aerosol- and droplet-producing behaviors, such as talking loudly and singing, [which] can set the conditions for large outbreaks,” the study authors wrote in the paper.

Nightlife and health care settings were both more likely to cause large outbreaks compared to dining, workplace, household, or other settings. Nightlife cases were also more likely to spread at the beginnings of waves 1 and 2 compared to the later stages of these waves. However, the risk of transmitting COVID-19 to various non-household settings was similar across age groups.

Onward transmission from households to non-household settings were higher, however. Households were not as likely to have large outbreaks, but many are intergenerational in nature and transmission could pose a higher risk of infection and death on older individuals, according to the study.

The study contains some limitations, the first being an underestimation of nightlife cases and overestimation of unknown cases because of self-reported outcomes. Additionally, cases were based on the most prevalent circulating strain of the time—therefore findings do not account for Omicron variant—and the study was conducted prior to available vaccinations.

“Surveillance and interventions targeting nightlife settings should be prioritized to disrupt COVID-19 transmission chains and prevent them from reaching populations with a high risk of death, especially in the early stage of a resurgence,” the study authors wrote in the article.

Reference

Imamura T, Watanabe A, Serizawa Y, et al. Transmission of COVID-19 in Nightlife, Household, and Health Care Settings in Tokyo, Japan, in 2020. February 24, 2023. JAMA Netw Open. 2023;6(2):e230589. doi:10.1001/jamanetworkopen.2023.0589