Probable airborne transmission of SARS-CoV-2 in a poorly ventilated restaurant

Abstract

Although airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been recognized, the condition of ventilation for its occurrence is still being debated. We analyzed a coronavirus disease 2019 (COVID-19) outbreak involving three families in a restaurant in Guangzhou, China, assessed the possibility of airborne transmission, and characterized the associated environmental conditions. We collected epidemiological data, obtained a full video recording and seating records from the restaurant, and measured the dispersion of a warm tracer gas as a surrogate for exhaled droplets from the index case. Computer simulations were performed to simulate the spread of fine exhaled droplets. We compared the in-room location of subsequently infected cases and spread of the simulated virus-laden aerosol tracer. The ventilation rate was measured using the tracer gas concentration decay method. This outbreak involved ten infected persons in three families (A, B, C). All ten persons ate lunch at three neighboring tables at the same restaurant on January 24, 2020. None of the restaurant staff or the 68 patrons at the other 15 tables became infected. During this occasion, the measured ventilation rate was 0.9 L/s per person. No close contact or fomite contact was identified, aside from back-to-back sitting in some cases. Analysis of the airflow dynamics indicates that the infection distribution is consistent with a spread pattern representative of long-range transmission of exhaled virus-laden aerosols. Airborne transmission of the SARS-CoV-2 virus is possible in crowded space with a ventilation rate of 1 L/s per person.

CFD Simulation of the Airborne Transmission of COVID-19 Vectors Emitted during Respiratory Mechanisms: Revisiting the Concept of Safe Distance

“… 26 Airflow patterns have been shown to be accountable for airborne transmission of SARS-CoV-2 in independent studies. 6 , 14 , 27 Complexities associated with airflow patterns also challenge the threshold-based approaches for defining safe distance as well as deducing general interpretations. The inefficacy of a fixed safe distance, its dependence on environmental conditions, and the recommendation to increase it beyond 2 m have been discussed in recently published studies.…”

Status: nosocomial transmission and prevention of SARS‐CoV‐2 in a Danish context

“…They conducted two tracer gas experiments to identify the airflow pattern. They concluded that droplet transmission could not alone explain the outbreak, since the distance between the index person and some of the other infected persons was greater the 4.6 m. They suggested that airflow from the air conditioner could have transported the droplets the long distance [53].…”

Analysis of efficacy of intervention strategies for COVID-19 transmission: A case study of Hong Kong

“…Many outbreaks showed that close contact including short-range airborne is the predominant route for SARS-CoV-2 transmission ( Chirizzi et al, 2021 , Zhang et al, 2020b ). Although some outbreaks such as a restaurant in Guangzhou ( Li et al, 2021 ) and a choir in Washington State, USA ( Hamner et al, 2020 ) showed the possibility of long-range airborne route, there is no solid evidence for its predominance. In this study, we assume that the short-range airborne transmission due to close contact predominates.…”