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Ou C, Hu S, Luo K, Yang H, Hang J, Cheng P, Hai Z, Xiao S, Qian H, Xiao S, Jing X, Xie Z, Ling H, Liu L, Gao L, Deng Q, Cowling BJ, Li Y. Insufficient ventilation led to a probable long-range airborne transmission of SARS-CoV-2 on two buses. Build Environ 2022; 207:108414. [PMID: 34629689 PMCID: PMC8487323 DOI: 10.1016/j.buildenv.2021.108414] [Citation(s) in RCA: 41] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 09/28/2021] [Accepted: 09/29/2021] [Indexed: 05/02/2023]
Abstract
Uncertainty remains on the threshold of ventilation rate in airborne transmission of SARS-CoV-2. We analyzed a COVID-19 outbreak in January 2020 in Hunan Province, China, involving an infected 24-year-old man, Mr. X, taking two subsequent buses, B1 and B2, in the same afternoon. We investigated the possibility of airborne transmission and the ventilation conditions for its occurrence. The ventilation rates on the buses were measured using a tracer-concentration decay method with the original driver on the original route. We measured and calculated the spread of the exhaled virus-laden droplet tracer from the suspected index case. Ten additional passengers were found to be infected, with seven of them (including one asymptomatic) on B1 and two on B2 when Mr. X was present, and one passenger infected on the subsequent B1 trip. B1 and B2 had time-averaged ventilation rates of approximately 1.7 and 3.2 L/s per person, respectively. The difference in ventilation rates and exposure time could explain why B1 had a higher attack rate than B2. Airborne transmission due to poor ventilation below 3.2 L/s played a role in this two-bus outbreak of COVID-19.
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Affiliation(s)
- Cuiyun Ou
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
| | - Shixiong Hu
- Hunan Provincial Center for Disease Control and Prevention, Changsha, China
| | - Kaiwei Luo
- Hunan Provincial Center for Disease Control and Prevention, Changsha, China
| | - Hongyu Yang
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
| | - Jian Hang
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
| | - Pan Cheng
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
| | - Zheng Hai
- Shaodong County Center for Disease Control and Prevention, Shaodong, China
| | - Shanliang Xiao
- Shaoyang City Center for Disease Control and Prevention, Shaoyang, China
| | - Hua Qian
- School of Energy and Environment, Southeast University, Nanjing, China
| | - Shenglan Xiao
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
| | - Xinping Jing
- Shaodong County Center for Disease Control and Prevention, Shaodong, China
| | - Zhengshen Xie
- Shaodong County Center for Disease Control and Prevention, Shaodong, China
| | - Hong Ling
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
| | - Li Liu
- School of Architecture, Tsinghua University, Beijing, China
| | - Lidong Gao
- Hunan Provincial Center for Disease Control and Prevention, Changsha, China
| | - Qihong Deng
- XiangYa School of Public Health, Central South University, Changsha, China
| | | | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
- School of Public Health, The University of Hong Kong, Hong Kong, China
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