Table 1. Possible sources of exposure based on behavioral histories from 14 days to 1 day before the onset.
| Activity type | Activity | n |
|---|---|---|
| Known high risk | ||
| Indoor dining | 21 | |
| Eating out with friends | 3 | |
| Ramen shop | 3 | |
| Soba shop | 2 | |
| Izakaya with friends | 2 | |
| Chinese restaurant | 2 | |
| Chinese restaurant | 1 | |
| Izakaya with friends | 1 | |
| A birthday party at a pub with close contact with about 30 people | 1 | |
| Japanese restaurant | 1 | |
| Company cafeteria | 1 | |
| Eating out with friends | 1 | |
| Eating out alone | 1 | |
| Eating out alone | 1 | |
| Order a home delivery service and have a meal with 4 people | 1 | |
| Indoor music events | 1 | |
| Attend a piano concert with vocalists | 1 | |
| Gyms | 2 | |
| Use of fitness club | 1 | |
| Instructor | 1 | |
| Others | ||
| Shopping | 34 | |
| Shopping at supermarkets | 8 | |
| Convenience store | 8 | |
| Shopping at supermarkets | 5 | |
| Convenience store | 3 | |
| Shopping at department stores | 2 | |
| Florist | 2 | |
| Convenience store | 1 | |
| Convenience store | 1 | |
| Shopping at department stores | 1 | |
| Real estate agent | 1 | |
| Pharmacy | 1 | |
| Bicycle shop | 1 | |
| Workplace/work-related | 22 | |
| Meetings and interviews at the workplace | 10 | |
| 1-2-hour conversation with colleague after work - colleague tested positive | 3 | |
| Meetings and interviews at the workplace | 2 | |
| Teaching karaoke | 1 | |
| One-on-one lessons as an instructor | 1 | |
| Office work at a facility for the disabled | 1 | |
| Cleaning the bullet train | 1 | |
| Transportation of users of the facility | 1 | |
| Serving customers at cafe | 1 | |
| Brushing teeth in the bathroom at work | 1 | |
| Public transportation and transportation-related | 31 | |
| Bicycling | 8 | |
| Commute by train | 5 | |
| Bicycling | 4 | |
| Commute by foot | 4 | |
| Commute by train | 3 | |
| Commute by foot | 2 | |
| Commute to work | 2 | |
| Commute by train | 1 | |
| Commute by foot | 1 | |
| Commute by cab | 1 | |
| Medical institution | 14 | |
| Clinic | 5 | |
| Vaccination site | 3 | |
| Hospital | 2 | |
| Hospital | 1 | |
| Clinic | 1 | |
| Dentist | 1 | |
| Dentist | 1 | |
| Leisure | 6 | |
| A walk | 3 | |
| Golf with family and friends | 2 | |
| A walk in the red-light district | 1 | |
| Others | 11 | |
| Use of delivery service | 2 | |
| Bank | 2 | |
| Bank | 1 | |
| Meeting with a friend who tested positive | 1 | |
| Hotel (cleaning staff's work was messy) | 1 | |
| Barbershop | 1 | |
| Barbershop | 1 | |
| Visit of the glass replacement company | 1 | |
| Visit to relative's house | 1 |
Places where the mask was removed are underlined. Activities that took place 4 to 7 days before the onset are in bold.