A cluster of tertiary transmissions of 2019 novel coronavirus (SARS-CoV-2) in the community from infectors with common cold symptoms

Background/Aims: As the global impact of the novel coronavirus disease 2019 (COVID-19) has been severe, many countries have intensified containment activities to eliminate virus transmission, through early detection and isolation strategies. To establish a proper quarantine strategy, it is essential to understand how easily the virus can spread in the communities. Methods: In this study, we collected detailed information on the circumstances in which human-to-human transmission occurred in the tertiary transmission cases of COVID-19 in the community. Results: On January 26, 2020, an imported case of COVID-19 was confirmed, and by February 10, 2020, one secondary transmission and three tertiary transmissions were identified. Secondary transmission occurred on the first day of illness of the infector, and his symptoms were suggestive of a common cold. The transmission occurred during a 90-minute long meal together in a restaurant. The people were sitting within one meter of each other, and had no direct contact. The tertiary transmission also occurred on the first-day illness of the other infector, and his only symptom was slight chills. The transmission occurred at a church during 2-hour-long worship, and two rows separated them. Conclusions: Our findings suggest that mildly symptomatic patients with COVID-19 could transmit the virus from the first day of illness through daily activities in the community. Early detection and isolation of patients with COVID-19 may be challenging.