Research Results

Research Study on the Risk of Infection with COVID-19 at So-called Nightlife Businesses in Shinjuku Ward(Interim Report)

Infectious Agents Surveillance Report (IASR)
Published on December 28, 2020
See below for excerpts and details (in Japanese)

Subjects and Method

This research has been conducted since July 2020, and its subjects were host clubs in Kabukicho, Shinjuku Ward, Tokyo which had offered to cooperate and their employees who were aged 20 or older. Site visit at clubs, interviews with their representatives, questionnaires to their employees, and PCR tests using saliva and serology tests (using Elecsys® Anti-SARS-CoV-2 by Roche Diagnostics) for SARS-CoV-2. Questionnaires and PCR and antibody tests are conducted approximately every month (ongoing as of October 20).

In addition, interviews with the representatives of host club groups and the executives of hostess clubs were held to assess the situation regarding infection prevention measures and awareness of infection prevention measures in Kabukicho (including businesses other than host clubs). The investigative results were described and whether known risk factors were present.

In order to assess the risk of infection right before a positive case was found, the behaviors of individual employees described in the questionnaires shown in the main text were how they behaved after May until a positive case was detected in respective clubs (late June to Mid-July in all clubs).

Case Definition

A SARS-CoV-2 infected individual (hereinafter referred to as an infected individual) was defined as an individual who had been found positive in the past PCR test, and an individual who was found positive with a saliva PCR test or antibody test in this research [samples equal to or greater than the value specified by the manufacturer (coi ≥ 1) were deemed antibody positive]. In addition, a symptomatic individual was defined as an individual who experienced a fever, cough, sore throat, difficulty breathing, malaise, loss of taste or smell, headache, or diarrhea, but was not diagnosed with other infectious diseases.


As of October 20, 68 persons from 4 establishments participated in this research (21 from Club A, 5 from Club B, 21 from Club C, and 21 from Club D). The results from three clubs are based on first three surveys, and results from one club is based on first two surveys. It was identified that all of the establishments had Infected Individuals among their employees before the research began. The numbers of Infected Individuals were 31 (46%) in total [9 (43%) at Club A, 2 (40%) at Club B, 9 (43%) at Club C, and 11 (52%) at Club D]. In addition, there were 7 individuals (10%) who were found for the first time through this research that they had been infected (all of them were found to be positive by antibody testing). Out of the 31 infected individuals, 26 (84%) were symptomatic.

The questionnaires to the employees found that the median age was 26 (between 20-47), and 46 individuals (68%) were living in Shinjuku Ward, 28 (41%) in company-rented housing (e.g., dormitories), and 32 (47%) with roommates. With regard to the situation on infection prevention measures in the club, 42 people (62%) were wearing masks for 75% or more of the time while serving customers, 50 (74%) were taking their temperature and checking their symptoms before going to work, and 39 (57%) replied that less than 50% of their customers wore masks. With regard to their behaviors outside of the clubs, 51 people (75%) were wearing masks for 75% or more of the time, 34 (50%) came to work accompanied by a customer or went to an afterhours date (employees and customers go out for food, drinks, etc. after business hours together) at least once a week, one (1%) went to other nightlife businesses at least once a week, and 11 (16%) went to crowded places other than their own clubs at least once a week. With regard to the degree of intoxication, out of 47, 39, and 27 people who would drink during work (around 19:00-2:00), during afterhours (around 2:00-5:00), and in the morning (around 5:00-10:00) respectively, 10 (21%), 13 (33%), and 8 (30%) would get heavily drunk or impaired.

Through interviews with the representatives of the four clubs, three of them were found to have begun strengthening their prevention measures against infection in early May, when the request to refrain from business operation was lifted, and were taking actions. These included having their employees wear masks in the clubs; thoroughly taking temperatures when arriving at work and suspending employees from work if they had any symptoms; thoroughly sanitizing customers' hands and taking temperatures when entering the premises; limiting the number of customers allowed to stay at a time; frequently cleaning (disinfecting) the environment; refraining from drinking by passing around cups, champagne calls, and events; and ventilating the premises as much as possible. On the other hand, there were also opinions that pointed out low mask-wearing rates among customers, a decline in awareness of infection prevention caused by intoxication during late night hours, afterhours, etc., and so on. The site visits found improper use and management of disinfectants, and structures that made it difficult to ventilate establishments (with no windows or with windows that cannot be opened, etc., because the Act on Control and Improvement of Amusement Business, Etc. specifies that the structure of the businesses must be such that the inside of the guest room is not easily visible from the outside).


The so-called "nightlife businesses" are prone to the "three Cs": closed spaces, crowded places, and close-contact settings. At the four clubs which participated in this research, the infection rates among the employees as at the time of research were high between 40-52%. Also, 10% of infections were newly discovered via antibody test during the study (all of them had symptoms in the past). These results indicates that many employees, including those who had gone undetected, had been infected.

While all of the participating clubs in this research have had multiple cases of infected individuals, most of them had implemented general measures to prevent infections as much as possible from before infections among employees were detected. These included wearing masks (one establishment implemented this after an infected individual was found); sanitizing hands when entering the club; disinfecting shared items and facilities; checking temperature and symptoms of customers when entering the premises; and health monitoring of the employees. The employees were also following the clubs’ policy on infection prevention measures. However, it was also discovered that they were not keeping health check records, using inappropriate disinfectants (they were using hypochlorous acid solution which is subject to many restrictions in terms of how to manage and use it unlike alcohol that's recommended), having difficulty ventilating the premises, and having customers practice infection prevention measures. In addition, it's considered that there were infection risks associated with a possible decline in awareness of measures against infection caused by intoxication during late night hours and afterhours, social background such as group living settings, and behaviors of the employees outside work. One limitation is that we were unable to conduct interviews on customers or test them for present or past infections.

Based on the efforts of other businesses in Kabukicho for infection prevention that we found out through interviews, the clubs that participated in this research were considered to be so-called “good clubs”, which were taking measures against the spread of infection relatively eagerly. The Kabukicho area as well as Shinjuku Ward are working hard to improve prevention measures through various innovative approaches, and working toward enhancing infection prevention measures in the area as a whole ( In addition to these, our study indicated that informing customers regarding infection prevention measures and asking for their cooperation, and ensuring that employees practice infection prevention measures, both in and outside the work setting are important to prevent the spread of the virus.