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Zhang N, Yang X, Su B, Dou Z. Analysis of SARS-CoV-2 transmission in a university classroom based on real human close contact behaviors. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 917:170346. [PMID: 38281642 DOI: 10.1016/j.scitotenv.2024.170346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 12/29/2023] [Accepted: 01/19/2024] [Indexed: 01/30/2024]
Abstract
Due to high-population density, frequent close contact, possible poor ventilation, university classrooms are vulnerable for transmission of respiratory infectious diseases. Close contact and long-range airborne are possibly main routes for SARS-CoV-2 transmission. In this study, taking a university classroom in Beijing for example, close contact behaviors of students were collected through a depth-detection device, which could detect depth to each pixel of the image, based on semi-supervised learning. Finally, >23 h of video data were obtained. Using Computational Fluid Dynamics, the relationship between viral exposure and close contact behaviors (e.g. interpersonal distance, relative facial orientations, and relative positions) was established. A multi-route transmission model (short-range airborne, mucous deposition, and long-range airborne) of infectious diseases considering real close contact behaviors was developed. In the case of Omicron, the risk of infection in university classrooms and the efficacy of different interventions were assessed based on dose-response model. The average interpersonal distance in university classrooms is 0.9 m (95 % CI, 0.5 m-1.4 m), with the highest proportion of face-to-back contact at 87.0 %. The risk of infection of susceptible students per 45-min lesson was 1 %. The relative contributions of short-range airborne and long-range airborne transmission were 40.5 % and 59.5 %, respectively, and the mucous deposition was basically negligible. When all students are wearing N95 respirators, the infection risk could be reduced by 96 %, the relative contribution of long-range airborne transmission increases to 95.6 %. When the fresh air per capita in the classroom is 24 m3/h/person, the virus exposure could be decreased by 81.1 % compared to the real situation with 1.02 m3/h/person. In a classroom with an occupancy rate of 50 %, after optimized arrangement of student distribution, the infection risk could be decreased by 62 %.
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Affiliation(s)
- Nan Zhang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Xueze Yang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Boni Su
- China Electric Power Planning & Engineering Institute, Beijing, China
| | - Zhiyang Dou
- Department of Computer Science, The University of Hong Kong, Hong Kong, China.
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Zhang N, Liu L, Dou Z, Liu X, Yang X, Miao D, Guo Y, Gu S, Li Y, Qian H, Wei J. Close contact behaviors of university and school students in 10 indoor environments. JOURNAL OF HAZARDOUS MATERIALS 2023; 458:132069. [PMID: 37463561 DOI: 10.1016/j.jhazmat.2023.132069] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 05/24/2023] [Accepted: 07/13/2023] [Indexed: 07/20/2023]
Abstract
Close contact routes, including short-range airborne and large-droplet routes, play an important role in the transmission of SARS-CoV-2 in indoor environments. However, the exposure risk of such routes is difficult to quantify due to the lack of data on the close contact behavior of individuals. In this study, a digital wearable device, based on semi-supervised learning, was developed to automatically record human close contact behavior. We collected 337,056 s of indoor close contact of school and university students from 194.5 h of depth video recordings in 10 types of indoor environments. The correlation between aerosol exposure and close contact behaviors was then evaluated. Individuals in restaurants had the highest close contact ratio (64%), as well as the highest probability of face-to-face pattern (78%) during close contact. Accordingly, university students showed greater exposure potential in dormitories than school students in homes, however, a lower exposure was observed in classrooms and postgraduate student offices in comparison with school students in classrooms. In addition, restaurants had the highest aerosol exposure volume for both short-range inhalation and direct deposition on the facial mucosa. Thus, the classroom was established as the primary indoor environment where school students are exposed to aerosols.
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Affiliation(s)
- Nan Zhang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Li Liu
- School of Architecture, Tsinghua University, Beijing, China
| | - Zhiyang Dou
- Department of Computer Science, The University of Hong Kong, Hong Kong, China
| | - Xiyue Liu
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Xueze Yang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Doudou Miao
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Yong Guo
- Department of Building Science, Tsinghua University, Beijing, China
| | - Silan Gu
- Thee First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
| | - Hua Qian
- School of Energy and Environment, Southeast University, Nanjing, China
| | - Jianjian Wei
- Institute of Refrigeration and Cryogenics, Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Zhejiang University, Hangzhou, China.
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Guo Y, Dou Z, Zhang N, Liu X, Su B, Li Y, Zhang Y. Student close contact behavior and COVID-19 transmission in China's classrooms. PNAS NEXUS 2023; 2:pgad142. [PMID: 37228510 PMCID: PMC10205473 DOI: 10.1093/pnasnexus/pgad142] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 04/10/2023] [Accepted: 04/14/2023] [Indexed: 05/27/2023]
Abstract
Classrooms are high-risk indoor environments, so analysis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission in classrooms is important for determining optimal interventions. Due to the absence of human behavior data, it is challenging to accurately determine virus exposure in classrooms. A wearable device for close contact behavior detection was developed, and we recorded >250,000 data points of close contact behaviors of students from grades 1 to 12. Combined with a survey on students' behaviors, we analyzed virus transmission in classrooms. Close contact rates for students were 37 ± 11% during classes and 48 ± 13% during breaks. Students in lower grades had higher close contact rates and virus transmission potential. The long-range airborne transmission route is dominant, accounting for 90 ± 3.6% and 75 ± 7.7% with and without mask wearing, respectively. During breaks, the short-range airborne route became more important, contributing 48 ± 3.1% in grades 1 to 9 (without wearing masks). Ventilation alone cannot always meet the demands of COVID-19 control; 30 m3/h/person is suggested as the threshold outdoor air ventilation rate in a classroom. This study provides scientific support for COVID-19 prevention and control in classrooms, and our proposed human behavior detection and analysis methods offer a powerful tool to understand virus transmission characteristics and can be employed in various indoor environments.
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Affiliation(s)
- Yong Guo
- Department of Building Science, Tsinghua University, Beijing 100084, China
- Beijing Key Laboratory of Indoor Air Quality Evaluation and Control, Beijing 100084, China
| | - Zhiyang Dou
- Department of Computer Science, The University of Hong Kong, Beijing 999077, China
| | - Nan Zhang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing 100124, China
| | - Xiyue Liu
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing 100124, China
| | - Boni Su
- Clean Energy Research Institute, China Electric Power Planning and Engineering Institute, Beijing 100120, China
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR 999077, China
| | - Yinping Zhang
- Department of Building Science, Tsinghua University, Beijing 100084, China
- Beijing Key Laboratory of Indoor Air Quality Evaluation and Control, Beijing 100084, China
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Addressing Complexity in the Pandemic Context: How Systems Thinking Can Facilitate Understanding of Design Aspects for Preventive Technologies. INFORMATICS 2023. [DOI: 10.3390/informatics10010007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The COVID-19 pandemic constitutes a wicked problem that is defined by rapidly evolving and dynamic conditions, where the physical world changes (e.g., pathogens mutate) and, in parallel, our understanding and knowledge rapidly progress. Various preventive measures have been developed or proposed to manage the situation, including digital preventive technologies to support contact tracing or physical distancing. The complexity of the pandemic and the rapidly evolving nature of the situation pose challenges for the design of effective preventive technologies. The aim of this conceptual paper is to apply a systems thinking model, DSRP (distinctions, systems, relations, perspectives) to explain the underlying assumptions, patterns, and connections of the pandemic domain, as well as to identify potential leverage points for design of preventive technologies. Two different design approaches, contact tracing and nudging for distance, are compared, focusing on how their design and preventive logic are related to system complexity. The analysis explains why a contact tracing technology involves more complexity, which can challenge both implementation and user understanding. A system utilizing nudges can operate using a more distinct system boundary, which can benefit understanding and implementation. However, frequent nudges might pose challenges for user experience. This further implies that these technologies have different contextual requirements and are useful at different levels in society. The main contribution of this work is to show how systems thinking can organize our understanding and guide the design of preventive technologies in the context of epidemics and pandemics.
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Wang JX, Wu Z, Wang H, Zhong M, Mao Y, Li Y, Wang M, Yao S. Ventilation reconstruction in bathrooms for restraining hazardous plume: Mitigate COVID-19 and beyond. JOURNAL OF HAZARDOUS MATERIALS 2022; 439:129697. [PMID: 36104926 PMCID: PMC9335364 DOI: 10.1016/j.jhazmat.2022.129697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 07/11/2022] [Accepted: 07/27/2022] [Indexed: 05/20/2023]
Abstract
Converging evidence reports that the probability of vertical transmission patterns via shared drainage systems, may be responsible for the huge contactless community outbreak in high-rise buildings. Publications indicate that a faulty bathroom exhaust fan system is ineffective in removing lifted hazardous virus-laden aerosols from the toilet bowl space. Common strategies (boosting ventilation capability and applying disinfection tablets) seem unsustainable and remain to date untested. Using combined simulation and experimental approaches, we compared three ventilation schemes in a family bathroom including the traditional ceiling fan, floor fan, and side-wall fan. We found that the traditional ceiling fan was barely functional whereby aerosol particles were not being adequately removed. Conversely, a side-wall fan could function efficiently and an enhanced ventilation capability can have increased performance whereby nearly 80.9% of the lifted aerosol particles were removed. There exists a common, and easily-overlooked mistake in the layout of the bathroom, exposing occupants to a contactless vertical pathogen aerosol transmission route. Corrections and dissemination are thus imperative for the reconstruction of these types of family bathrooms. Our findings provide evidence for the bathroom and smart ventilation system upgrade, promoting indoor public health and human hygiene.
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Affiliation(s)
- Ji-Xiang Wang
- College of Electrical, Energy and Power Engineering, Yangzhou University, Yangzhou 225009, PR China; Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China.
| | - Zhe Wu
- College of Electrical, Energy and Power Engineering, Yangzhou University, Yangzhou 225009, PR China
| | - Hongmei Wang
- College of Electrical, Energy and Power Engineering, Yangzhou University, Yangzhou 225009, PR China
| | - Mingliang Zhong
- Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, PR China
| | - Yufeng Mao
- Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, PR China
| | - Yunyun Li
- School of Energy and Environment, Southeast University, Nanjing 210096, PR China
| | - Mengxiao Wang
- Department of Traditional Chinese Medicine, Tianjin Medical University General Hospital, Tianjin 300052, PR China
| | - Shuhuai Yao
- Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China; Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China.
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