251
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Coleman KK, Tay DJW, Sen Tan K, Ong SWX, Son TT, Koh MH, Chin YQ, Nasir H, Mak TM, Chu JJH, Milton DK, Chow VTK, Tambyah PA, Chen M, Wai TK. Viral Load of SARS-CoV-2 in Respiratory Aerosols Emitted by COVID-19 Patients while Breathing, Talking, and Singing. Clin Infect Dis 2021; 74:1722-1728. [PMID: 34358292 PMCID: PMC8436389 DOI: 10.1093/cid/ciab691] [Citation(s) in RCA: 111] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Indexed: 11/14/2022] Open
Abstract
Background Multiple SARS-CoV-2 superspreading events suggest that aerosols play an important role in driving the COVID-19 pandemic. To better understand how airborne SARS-CoV-2 transmission occurs, we sought to determine viral loads within coarse (>5μm) and fine (≤5μm) respiratory aerosols produced when breathing, talking, and singing. Methods Using a G-II exhaled breath collector, we measured viral RNA in coarse and fine respiratory aerosols emitted by COVID-19 patients during 30 minutes of breathing, 15 minutes of talking, and 15 minutes of singing. Results Thirteen participants (59%) emitted detectable levels of SARS-CoV-2 RNA in respiratory aerosols, including 3 asymptomatic and 1 presymptomatic patient. Viral loads ranged from 63–5,821 N gene copies per expiratory activity per participant, with high person-to-person variation. Patients earlier in illness were more likely to emit detectable RNA. Two participants, sampled on day 3 of illness, accounted for 52% of the total viral load. Overall, 94% of SARS-CoV-2 RNA copies were emitted by talking and singing. Interestingly, 7 participants emitted more virus from talking than singing. Overall, fine aerosols constituted 85% of the viral load detected in our study. Virus cultures were negative. Conclusions Fine aerosols produced by talking and singing contain more SARS-CoV-2 copies than coarse aerosols and may play a significant role in SARS-CoV-2 transmission. Exposure to fine aerosols, especially indoors, should be mitigated. Isolating viable SARS-CoV-2 from respiratory aerosol samples remains challenging, and whether this can be more easily accomplished for emerging SARS-CoV-2 variants is an urgent enquiry necessitating larger-scale studies.
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Affiliation(s)
- Kristen K Coleman
- Programme in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore
| | - Douglas Jie Wen Tay
- Department of the Built Environment, National University of Singapore, Singapore
| | - Kai Sen Tan
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore.,Department of Otolaryngology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore.,Infectious Diseases Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore.,Biosafety Level 3 Core Facility, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
| | - Sean Wei Xiang Ong
- National Centre for Infectious Diseases, Singapore.,Department of Infectious Diseases, Tan Tock Seng Hospital, Singapore
| | - Than The Son
- Programme in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore.,Department of the Built Environment, National University of Singapore, Singapore
| | - Ming Hui Koh
- Department of the Built Environment, National University of Singapore, Singapore
| | - Yi Qing Chin
- National Centre for Infectious Diseases, Singapore
| | - Haziq Nasir
- Division of Infectious Diseases, Department of Medicine, National University Health System, National University of Singapore, Singapore
| | - Tze Minn Mak
- National Centre for Infectious Diseases, Singapore
| | - Justin Jang Hann Chu
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore.,Infectious Diseases Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore.,Biosafety Level 3 Core Facility, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore.,Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore
| | - Donald K Milton
- Maryland Institute for Applied Environmental Health, University of Maryland School of Public Health, USA
| | - Vincent T K Chow
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore.,Infectious Diseases Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
| | - Paul Anantharajah Tambyah
- Infectious Diseases Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore.,Division of Infectious Diseases, Department of Medicine, National University Health System, National University of Singapore, Singapore
| | - Mark Chen
- National Centre for Infectious Diseases, Singapore.,Department of Infectious Diseases, Tan Tock Seng Hospital, Singapore
| | - Tham Kwok Wai
- Department of the Built Environment, National University of Singapore, Singapore
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252
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Budaev S. Safety and Reverence: How Roman Catholic Liturgy Can Respond to the COVID-19 Pandemic. JOURNAL OF RELIGION AND HEALTH 2021; 60:2331-2352. [PMID: 34031781 PMCID: PMC8143074 DOI: 10.1007/s10943-021-01282-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/08/2021] [Indexed: 05/24/2023]
Abstract
The current COVID-19 pandemic is a major challenge for many religious denominations. The Roman Catholic Church strongly depends on physical communal worship and sacraments. Disagreements grow concerning the best balance between safety and piety. To address this issue, I review the major transmission risks for the SARS-CoV-2 virus and list certain measures to enhance the safety of the Roman Catholic Liturgy without compromising its intrinsic beauty and reverent spiritual attitude. This can be achieved through assimilation of several traditional elements into the modern liturgy. I emphasize that religious leadership and decision-making should be transparent and based on inclusiveness, pluralism, best scientific evidence and voluntary cooperation.
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Affiliation(s)
- Sergey Budaev
- Department of Biological Sciences, University of Bergen, Postboks 7803, 5020, Bergen, Norway.
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253
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Hill SC, Mackowski DW, Doughty DC. Shielding of viruses such as SARS-Cov-2 from ultraviolet radiation in particles generated by sneezing or coughing: Numerical simulations of survival fractions. JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 2021; 18:394-408. [PMID: 34161194 DOI: 10.1080/15459624.2021.1939877] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
SARS-CoV-2 and other microbes within aerosol particles can be partially shielded from UV radiation. The particles refract and absorb light, and thereby reduce the UV intensity at various locations within the particle. Previously, we demonstrated shielding in calculations of UV intensities within spherical approximations of SARS-CoV-2 virions within spherical particles approximating dried-to-equilibrium respiratory fluids. The purpose of this paper is to extend that work to survival fractions of virions (i.e., fractions of virions that can infect cells) within spherical particles approximating dried respiratory fluids, and to investigate the implications of these calculations for using UV light for disinfection. The particles may be on a surface or in air. Here, the survival fraction (S) of a set of individual virions illuminated with a UV fluence (F, in J/m2) is assumed described by S(kF) = exp(-kF), where k is the UV inactivation rate constant (m2/J). The average survival fraction (Sp) of the simulated virions in a group of particles is calculated using the energy absorbed by each virion in the particles. The results show that virions within particles of dried respiratory fluids can have larger Sp than do individual virions. For individual virions, and virions within 1-, 5-, and 9-µm particles illuminated (normal incidence) on a surface with 260-nm UV light, the Sp = 0.00005, 0.0155, 0.22, and 0.28, respectively, when kF = 10. The Sp decrease to <10-7, <10-7, 0.077, and 0.15, respectively, for kF = 100. Results also show that illuminating particles with UV beams from widely separated directions can strongly reduce the Sp. These results suggest that the size distributions and optical properties of the dried particles of virion-containing respiratory fluids are likely important to effectively designing and using UV germicidal irradiation systems for microbes in particles. The results suggest the use of reflective surfaces to increase the angles of illumination and decrease the Sp. The results suggest the need for measurements of the Sp of SARS-CoV-2 in particles having compositions and sizes relevant to the modes of disease transmission.
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254
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Bak A, Mugglestone MA, Ratnaraja NV, Wilson JA, Rivett L, Stoneham SM, Bostock J, Moses SE, Price JR, Weinbren M, Loveday HP, Islam J, Wilson APR. SARS-CoV-2 routes of transmission and recommendations for preventing acquisition: joint British Infection Association (BIA), Healthcare Infection Society (HIS), Infection Prevention Society (IPS) and Royal College of Pathologists (RCPath) guidance. J Hosp Infect 2021; 114:79-103. [PMID: 33940093 PMCID: PMC8087584 DOI: 10.1016/j.jhin.2021.04.027] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 04/26/2021] [Accepted: 04/26/2021] [Indexed: 02/06/2023]
Affiliation(s)
- A Bak
- Healthcare Infection Society, UK.
| | | | - N V Ratnaraja
- British Infection Association, UK; University Hospitals Coventry & Warwickshire NHS Trust, UK
| | - J A Wilson
- Infection Prevention Society, UK; Richard Wells Research Centre, University of West London, UK
| | - L Rivett
- Healthcare Infection Society, UK; Cambridge University NHS Hospitals Foundation Trust, UK
| | - S M Stoneham
- Healthcare Infection Society, UK; Brighton and Sussex University Hospitals NHS Trust, UK
| | | | - S E Moses
- British Infection Association, UK; Royal College of Pathologists, UK; East Kent Hospitals University NHS Foundation Trust, UK
| | - J R Price
- Healthcare Infection Society, UK; Imperial College Healthcare NHS Trust, UK
| | - M Weinbren
- Healthcare Infection Society, UK; Sherwood Forest Hospitals NHS Foundation Trust, UK
| | - H P Loveday
- Infection Prevention Society, UK; Richard Wells Research Centre, University of West London, UK
| | - J Islam
- Healthcare Infection Society, UK; Brighton and Sussex University Hospitals NHS Trust, UK
| | - A P R Wilson
- Healthcare Infection Society, UK; University College London Hospitals NHS Foundation Trust, UK
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255
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Sodiq A, Khan MA, Naas M, Amhamed A. Addressing COVID-19 contagion through the HVAC systems by reviewing indoor airborne nature of infectious microbes: Will an innovative air recirculation concept provide a practical solution? ENVIRONMENTAL RESEARCH 2021; 199:111329. [PMID: 34004171 PMCID: PMC8123526 DOI: 10.1016/j.envres.2021.111329] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2021] [Revised: 03/22/2021] [Accepted: 05/11/2021] [Indexed: 05/03/2023]
Abstract
As the world continues to grapple with the reality of coronavirus disease, global research communities are racing to develop practical solutions to adjust to the new challenges. One such challenge is the control of indoor air quality in the COVID-19 era and beyond. Since COVID-19 became a global pandemic, the "super spread" of the virus has continued to amaze policymakers despite measures put in place by public health officials to sensitize the general public on the need for social distancing, personal hygiene, etc. In this work, we have reviewed the literature to demonstrate, by investigating the historical and present circumstances, that indoor spread of infectious diseases may be assisted by the conditions of the HVAC systems. While little consideration has been given to the possibility of indoor airborne transmission of the virus, the available reports have demonstrated that the virus, with average aerodynamic diameter up to 80-120 nm, is viable as aerosol in indoor atmosphere for more than 3 h, and its spread may be assisted by the HVAC systems. Having reviewed the vulnerability of the conventional ventilation systems, we recommend innovative air circulation concept supported by the use of UVGI in combination with nanoporous air filter to combat the spread of SARS-CoV-2 and other harmful microbes in enclosed spaces.
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Affiliation(s)
- Ahmed Sodiq
- Qatar Environment and Energy Institute (QEERI), Qatar.
| | | | - Mahmoud Naas
- Qatar Biomedical Research Institute, Hamad Bin Khalifa University, Doha, Qatar
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256
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Das D, Ramachandran G. Risk analysis of different transport vehicles in India during COVID-19 pandemic. ENVIRONMENTAL RESEARCH 2021; 199:111268. [PMID: 33984308 PMCID: PMC8110332 DOI: 10.1016/j.envres.2021.111268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 04/06/2021] [Accepted: 04/28/2021] [Indexed: 06/12/2023]
Abstract
Due to the airborne nature of viral particles, adequate ventilation has been identified as one suitable mitigation strategy for reducing their transmission. While 'dilution of air by opening the window' has been prescribed by national and international health agencies, unintended detrimental consequences might result in many developing countries with high ambient air pollution. In the present study, PM2.5 exposure concentration and probability of mortality due to PM2.5 in different scenarios were assessed. A COVID airborne infection risk estimator was used to estimate the probability of infection by aerosol transmission in various commuter micro-environments: (a) air conditioned (AC) taxi (b) non-AC taxi (c) bus and (d) autorickshaw. The following were the estimated exposure concentrations in the four types of vehicles during pre-lockdown, during lockdown, and lost-lockdown: AC taxi cars (17.16 μg/m3, 4.52 μg/m3, and 25.09 μg/m3); non-AC taxis: (28.74 μg/m3, 7.56 μg/m3, 42.01 μg/m3); buses (21.79 μg/m3, 5.73 μg/m3, 31.86 μg/m3) autorickshaws (51.30 μg/m3, 3.50 μg/m3, 75 μg/m3). Post-lockdown, the probability of mortality due to PM2.5 was highest for autorickshaws (5.67 × 10-3), followed by non-AC taxis (2.07 × 10-3), buses (1.39 × 10-3), and AC taxis (1.02 × 10-3). This order of risk is inverted for the probability of infection by SARS-COV-2, with the highest for AC taxis (6.10 × 10-2), followed by non-AC taxis (1.71 × 10-2), buses (1.42 × 10-2), and the lowest risk in autorickshaws (1.99 × 10-4). The findings of the present study suggest that vehicles with higher ventilation or air changes per hour (ACH) should be preferred over other modes of transport during COVID-19 pandemic.
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Affiliation(s)
- Darpan Das
- Johns Hopkins University, Bloomberg School of Public Health, Department of Environmental Health and Engineering, 615 N Wolfe St, Baltimore, MD, 21205, USA.
| | - Gurumurthy Ramachandran
- Johns Hopkins University, Bloomberg School of Public Health, Department of Environmental Health and Engineering, 615 N Wolfe St, Baltimore, MD, 21205, USA
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257
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Esteban Florez FL, Thibodeau T, Oni T, Floyd E, Khajotia SS, Cai C. Size-resolved spatial distribution analysis of aerosols with or without the utilization of a novel aerosol containment device in dental settings. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:085102. [PMID: 34471340 PMCID: PMC8404378 DOI: 10.1063/5.0056229] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 07/10/2021] [Indexed: 05/06/2023]
Abstract
The coronavirus disease 2019 pandemic has imposed unprecedented occupational challenges for healthcare professionals. In dentistry, handheld instruments such as air and electric handpieces, ultrasonic scalers, and air/water syringes are capable of generating aerosols, droplets, and splatter, thereby exposing dental professionals to airborne contaminants such as viruses, bacteria, and fungi. The objective of the present study was to determine the spatial distribution of aerosols by size (0.30 to 20.00 μm) and the efficacy of a novel aerosol containment device (ACD) in a large operatory room with 12 dental chairs. Real-time portable laser aerosol spectrometers were used to measure the size-resolved number concentration of aerosols generated by a collision nebulizer. Results reported demonstrate that aerosol number concentrations significantly decreased as a function of distance with or without the utilization of the ACD. The ACD was able to efficiently decrease (up to 8.56-fold) the number and size distribution of particles in a large dental clinic. The novel device demonstrated higher efficiency for particles shown to contain the highest levels of severe acute respiratory syndrome coronavirus 2 in Chinese hospitals, thereby showing great promise to potentially decrease the spreading of nosocomial pathogens in dental settings.
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Affiliation(s)
- Fernando Luis Esteban Florez
- Department of Restorative Sciences, Division of Dental Biomaterials, College of Dentistry, The University of Oklahoma Health Sciences Center, 1201 N. Stonewall Avenue, Oklahoma City, Oklahoma 73117, USA
| | - Tyler Thibodeau
- School of Industrial and Systems Engineering, The University of Oklahoma, 202 W. Boyd Street, Norman, Oklahoma 73019, USA
| | - Toluwanimi Oni
- Department of Occupational and Environmental Health, Hudson College of Public Health, The University of Oklahoma Health Sciences Center, 801 N.E. 13th Street, Oklahoma City, Oklahoma 73126, USA
| | - Evan Floyd
- Department of Occupational and Environmental Health, Hudson College of Public Health, The University of Oklahoma Health Sciences Center, 801 N.E. 13th Street, Oklahoma City, Oklahoma 73126, USA
| | - Sharukh S. Khajotia
- Department of Restorative Sciences, Division of Dental Biomaterials, College of Dentistry, The University of Oklahoma Health Sciences Center, 1201 N. Stonewall Avenue, Oklahoma City, Oklahoma 73117, USA
| | - Changjie Cai
- Department of Occupational and Environmental Health, Hudson College of Public Health, The University of Oklahoma Health Sciences Center, 801 N.E. 13th Street, Oklahoma City, Oklahoma 73126, USA
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258
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Abstract
Human respiratory virus infections lead to a spectrum of respiratory symptoms and disease severity, contributing to substantial morbidity, mortality and economic losses worldwide, as seen in the COVID-19 pandemic. Belonging to diverse families, respiratory viruses differ in how easy they spread (transmissibility) and the mechanism (modes) of transmission. Transmissibility as estimated by the basic reproduction number (R0) or secondary attack rate is heterogeneous for the same virus. Respiratory viruses can be transmitted via four major modes of transmission: direct (physical) contact, indirect contact (fomite), (large) droplets and (fine) aerosols. We know little about the relative contribution of each mode to the transmission of a particular virus in different settings, and how its variation affects transmissibility and transmission dynamics. Discussion on the particle size threshold between droplets and aerosols and the importance of aerosol transmission for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza virus is ongoing. Mechanistic evidence supports the efficacies of non-pharmaceutical interventions with regard to virus reduction; however, more data are needed on their effectiveness in reducing transmission. Understanding the relative contribution of different modes to transmission is crucial to inform the effectiveness of non-pharmaceutical interventions in the population. Intervening against multiple modes of transmission should be more effective than acting on a single mode.
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Affiliation(s)
- Nancy H L Leung
- WHO Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China.
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259
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Liu F, Luo Z, Li Y, Zheng X, Zhang C, Qian H. Revisiting physical distancing threshold in indoor environment using infection-risk-based modeling. ENVIRONMENT INTERNATIONAL 2021; 153:106542. [PMID: 33819720 PMCID: PMC8016632 DOI: 10.1016/j.envint.2021.106542] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 03/20/2021] [Accepted: 03/22/2021] [Indexed: 05/09/2023]
Abstract
Physical distancing has been an important policy to mitigate the spread of the novel coronavirus disease 2019 (COVID-19) in public settings. However, the current 1-2 m physical distancing rule is based on the physics of droplet transport and could not directly translate into infection risk. We therefore revisit the 2-m physical distancing rule by developing an infection-risk-based model for human speaking. The key modeling framework components include viral load, droplets dispersion and evaporation, deposition efficiency, viral dose-response rate and infection risk. The results suggest that the one-size-fits-all 2-m physical distancing rule derived from the pure droplet-physics-based model is not applicable under some realistic indoor settings, and may rather increase transmission probability of diseases. Especially, in thermally stratified environments, the infection risk could exhibit multiple peaks for a long distance beyond 2 m. With Sobol's sensitivity analysis, most variance of the risk is found to be significantly attributable to the variability in temperature gradient, exposure time and breathing height difference. Our study suggests there is no such magic 2 m physical distancing rule for all environments, but it needs to be used alongside other strategies, such as using face cover, reducing exposure time, and controlling the thermal stratification of indoor environment.
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Affiliation(s)
- Fan Liu
- School of Energy and Environment, Southeast University, Nanjing, China; School of the Built Environment, University of Reading, Reading, United Kingdom
| | - Zhiwen Luo
- School of the Built Environment, University of Reading, Reading, United Kingdom.
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong Special Administrative Region
| | - Xiaohong Zheng
- School of Energy and Environment, Southeast University, Nanjing, China; Jiangsu Provincial Key Laboratory of Solar Energy Science and Technology, School of Energy and Environment, Southeast University, Nanjing, China
| | - Chongyang Zhang
- School of Energy and Environment, Southeast University, Nanjing, China; Shanghai Research Institute of Building Sciences (Group) Co., Ltd., Shanghai, China
| | - Hua Qian
- School of Energy and Environment, Southeast University, Nanjing, China.
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260
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Zhang Z, Capecelatro J, Maki K. On the utility of a well-mixed model for predicting disease transmission on an urban bus. AIP ADVANCES 2021; 11:085229. [PMID: 34466279 PMCID: PMC8404159 DOI: 10.1063/5.0061219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 08/04/2021] [Indexed: 05/06/2023]
Abstract
The transport of virus-laden aerosols from a host to a susceptible person is governed by complex turbulent airflow and physics related to breathing, coughing and sneezing, mechanical and passive ventilation, thermal buoyancy effects, surface deposition, masks, and air filtration. In this paper, we study the infection risk via airborne transmission on an urban bus using unsteady Reynolds-averaged Navier-Stokes equations and a passive-scalar model of the virus-laden aerosol concentration. Results from these simulations are directly compared to the widely used well-mixed model and show significant differences in the concentration field and number of inhaled particles. Specifically, in the limit of low mechanical ventilation rates, the well-mixed model will overpredict the concentration far from the infected passenger and substantially underpredict the concentration near the infected passenger. The results reported herein also apply to other enclosed spaces.
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Affiliation(s)
- Zhihang Zhang
- Department of Naval Architecture and Marine
Engineering, University of Michigan, Ann Arbor, Michigan 48109-2145,
USA
| | - Jesse Capecelatro
- Department of Mechanical Engineering, University
of Michigan, Ann Arbor, Michigan 48109-2145, USA
| | - Kevin Maki
- Department of Naval Architecture and Marine
Engineering, University of Michigan, Ann Arbor, Michigan 48109-2145,
USA
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261
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Ooi CC, Suwardi A, Ou Yang ZL, Xu G, Tan CKI, Daniel D, Li H, Ge Z, Leong FY, Marimuthu K, Ng OT, Lim SB, Lim P, Mak WS, Cheong WCD, Loh XJ, Kang CW, Lim KH. Risk assessment of airborne COVID-19 exposure in social settings. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:087118. [PMID: 34552314 PMCID: PMC8450907 DOI: 10.1063/5.0055547] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 08/09/2021] [Indexed: 05/04/2023]
Abstract
The COVID-19 pandemic has led to many countries oscillating between various states of lock-down as they seek to balance keeping the economy and essential services running and minimizing the risk of further transmission. Decisions are made about which activities to keep open across a range of social settings and venues guided only by ad hoc heuristics regarding social distancing and personal hygiene. Hence, we propose the dual use of computational fluid dynamic simulations and surrogate aerosol measurements for location-specific assessment of risk of infection across different real-world settings. We propose a 3-tiered risk assessment scheme to facilitate classification of scenarios into risk levels based on simulations and experiments. Threshold values of <54 and >840 viral copies and <5% and >40% of original aerosol concentration are chosen to stratify low, medium, and high risk. This can help prioritize allowable activities and guide implementation of phased lockdowns or re-opening. Using a public bus in Singapore as a case study, we evaluate the relative risk of infection across scenarios such as different activities and passenger positions and demonstrate the effectiveness of our risk assessment methodology as a simple and easily interpretable framework. For example, this study revealed that the bus's air-conditioning greatly influences dispersion and increases the risk of certain seats and that talking can result in similar relative risk to coughing for passengers around an infected person. Both numerical and experimental approaches show similar relative risk levels with a Spearman's correlation coefficient of 0.74 despite differing observables, demonstrating applicability of this risk assessment methodology to other scenarios.
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Affiliation(s)
- Chin Chun Ooi
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, Singapore 138632
| | - Ady Suwardi
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore 138634
| | - Zhong Liang Ou Yang
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, Singapore 138632
| | - George Xu
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, Singapore 138632
| | - Chee Kiang Ivan Tan
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore 138634
| | - Dan Daniel
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore 138634
| | - Hongying Li
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, Singapore 138632
| | - Zhengwei Ge
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, Singapore 138632
| | - Fong Yew Leong
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, Singapore 138632
| | - Kalisvar Marimuthu
- National Centre for Infectious Diseases, Tan Tock Seng Hospital, 16 Jalan Tan Tock Seng, Singapore 308443
| | - Oon Tek Ng
- National Centre for Infectious Diseases, Tan Tock Seng Hospital, 16 Jalan Tan Tock Seng, Singapore 308443
| | - Shin Bin Lim
- Ministry of Health Singapore, College of Medicine Building, 16 College Road, Singapore 169854
| | - Peter Lim
- Land Transport Authority, 1 Hampshire Road, Singapore 219428
| | - Wai Siong Mak
- Land Transport Authority, 1 Hampshire Road, Singapore 219428
| | - Wun Chet Davy Cheong
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore 138634
| | - Xian Jun Loh
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore 138634
| | - Chang Wei Kang
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, Singapore 138632
| | - Keng Hui Lim
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, Singapore 138632
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262
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Zhang N, Chen X, Jia W, Jin T, Xiao S, Chen W, Hang J, Ou C, Lei H, Qian H, Su B, Li J, Liu D, Zhang W, Xue P, Liu J, Weschler LB, Xie J, Li Y, Kang M. Evidence for lack of transmission by close contact and surface touch in a restaurant outbreak of COVID-19. J Infect 2021; 83:207-216. [PMID: 34062182 PMCID: PMC8164346 DOI: 10.1016/j.jinf.2021.05.030] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 05/23/2021] [Accepted: 05/26/2021] [Indexed: 01/19/2023]
Abstract
BACKGROUND Coronavirus disease 2019 (COVID-19) is primarily a respiratory disease that has become a global pandemic. Close contact plays an important role in infection spread, while fomite may also be a possible transmission route. Research during the COVID-19 pandemic has identified long-range airborne transmission as one of the important transmission routes although lack solid evidence. METHODS We examined video data related to a restaurant associated COVID-19 outbreak in Guangzhou. We observed more than 40,000 surface touches and 13,000 episodes of close contacts in the restaurant during the entire lunch duration. These data allowed us to analyse infection risk via both the fomite and close contact routes. RESULTS There is no significant correlation between the infection risk via both fomite and close contact routes among those who were not family members of the index case. We can thus rule out virus transmission via fomite contact and interpersonal close contact routes in the Guangzhou restaurant outbreak. The absence of a fomite route agrees with the COVID-19 literature. CONCLUSIONS These results provide indirect evidence for the long-range airborne route dominating SARS-CoV-2 transmission in the restaurant. We note that the restaurant was poorly ventilated, allowing for increasing airborne SARS-CoV-2 concentration.
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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
| | - Xuguang Chen
- Guangdong Provincial Center for Disease Control and Prevention, Guangdong province, China
| | - Wei Jia
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong
| | - Tianyi Jin
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Shenglan Xiao
- School of Public Health (Shenzhen), Sun Yat-sen University, Guangzhou, China
| | - Wenzhao Chen
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong
| | - Jian Hang
- School of Atmospheric Sciences, Sun Yat-sen University, Guangzhou, China
| | - Cuiyun Ou
- School of Atmospheric Sciences, Sun Yat-sen University, Guangzhou, China
| | - Hao Lei
- School of Public Health, Zhejiang University, Hangzhou, Zhejiang, China
| | - Hua Qian
- School of Energy and Environment, Southeast University, Nanjing, China
| | - Boni Su
- China Electric Power Planning & Engineering Institute, Beijing, China
| | - Jiansen Li
- Guangdong Provincial Center for Disease Control and Prevention, Guangdong province, China
| | - Dongmei Liu
- Fogang County Center for Disease Control and Prevention, Guangdong, China
| | - Weirong Zhang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Peng Xue
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Jiaping Liu
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | | | - Jingchao Xie
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China.
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong; School of Public Health, The University of Hong Kong, Pokfulam Road, Hong Kong.
| | - Min Kang
- Guangdong Provincial Center for Disease Control and Prevention, Guangdong province, China; School of Public Health, Southern Medical University, Guangzhou, China.
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263
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Chaudhuri S, Saha A, Basu S. An opinion on the multiscale nature of Covid-19 type disease spread. Curr Opin Colloid Interface Sci 2021; 54:101462. [PMID: 33967585 PMCID: PMC8088079 DOI: 10.1016/j.cocis.2021.101462] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Recognizing the multiscale, interdisciplinary nature of the Covid-19 transmission dynamics, we discuss some recent developments concerning an attempt to construct a disease spread model from the flow physics of infectious droplets and aerosols and the frequency of contact between susceptible individuals with the infectious aerosol cloud. Such an approach begins with the exhalation event-specific, respiratory droplet size distribution (both airborne/aerosolized and ballistic droplets), followed by tracking its evolution in the exhaled air to estimate the probability of infection and the rate constants of the disease spread model. The basic formulations and structure of submodels, experiments involved to validate those submodels, are discussed. Finally, in the context of preventive measures, respiratory droplet-face mask interactions are described.
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Affiliation(s)
- Swetaprovo Chaudhuri
- Institute for Aerospace Studies, University of Toronto, Toronto, ON M3H 5T6, Canada
| | - Abhishek Saha
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA 92093, USA
| | - Saptarshi Basu
- Department of Mechanical Engineering, Indian Institute of Science, Bengaluru, KA 560012, India
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264
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Aerosol emission in professional singing of classical music. Sci Rep 2021; 11:14861. [PMID: 34290265 PMCID: PMC8295351 DOI: 10.1038/s41598-021-93281-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 06/23/2021] [Indexed: 02/08/2023] Open
Abstract
In this study, emission rates of aerosols emitted by professional singers were measured with a laser particle counter under cleanroom conditions. The emission rates during singing varied between 753 and 6093 particles/sec with a median of 1537 particles/sec. Emission rates for singing were compared with data for breathing and speaking. Significantly higher emission rates were found for singing. The emission enhancements between singing and speaking were between 4.0 and 99.5 with a median of 17.4, largely due to higher sound pressure levels when singing. Further, significant effects of vocal loudness were found, whereas there were no significant differences between the investigated voice classifications. The present study supports the efforts to improve the risk management in cases of possible aerogenic virus transmission, especially for choir singing.
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265
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Maestre JP, Jarma D, Yu JRF, Siegel JA, Horner SD, Kinney KA. Distribution of SARS-CoV-2 RNA signal in a home with COVID-19 positive occupants. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 778:146201. [PMID: 34030356 PMCID: PMC7942153 DOI: 10.1016/j.scitotenv.2021.146201] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 02/24/2021] [Accepted: 02/25/2021] [Indexed: 05/05/2023]
Abstract
Although many COVID-19 patients isolate and recover at home, the dispersal of SARS-CoV-2 onto surfaces and dust within the home environment remains poorly understood. To investigate the distribution and persistence of SARS-CoV-2 in a home with COVID-19 positive occupants, samples were collected from a household with two confirmed COVID-19 cases (one adult and one child). Home surface swab and dust samples were collected two months after symptom onset (and one month after symptom resolution) in the household. The strength of the SARS-CoV-2 molecular signal in fomites varied as a function of sample location, surface material and cleaning practices. Notably, the SARS-CoV-2 RNA signal was detected at several locations throughout the household although cleaning appears to have attenuated the signal on many surfaces. Of the 24 surfaces sampled, 46% were SARS-CoV-2 positive at the time of sampling. The SARS-CoV-2 concentrations in dust recovered from floor and HVAC filter samples ranged from 104 to 105 N2 gene copies/g dust. While detection of viral RNA does not imply infectivity, this study confirms that the SARS-CoV-2 RNA signal can be detected at several locations within a COVID-19 isolation home and can persist after symptoms have resolved. In addition, the concentration of SARS-CoV-2 (normalized per unit mass of dust) recovered in home HVAC filters may prove useful for estimating SARS-CoV-2 airborne levels in homes. In this work, using the quantitative filter forensics methodology, we estimated an average integrated airborne SARS-CoV-2 concentration of 69 ± 43 copies/m3. This approach can be used to help building scientists and engineers develop best practices in homes with COVID-19 positive occupants.
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Affiliation(s)
- Juan P Maestre
- Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, Austin, TX, USA
| | - David Jarma
- Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Jia-Rong F Yu
- Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Jeffrey A Siegel
- Department of Civil and Mineral Engineering, University of Toronto, Toronto, Ontario, Canada; Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
| | - Sharon D Horner
- School of Nursing, The University of Texas at Austin, TX, USA
| | - Kerry A Kinney
- Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, Austin, TX, USA.
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266
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Blumberg S, Lu P, Hoover CM, Lloyd-Smith JO, Kwan AT, Sears D, Bertozzi SM, Worden L. Mitigating outbreaks in congregate settings by decreasing the size of the susceptible population. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2021:2021.07.05.21260043. [PMID: 34268514 PMCID: PMC8282103 DOI: 10.1101/2021.07.05.21260043] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
While many transmission models have been developed for community spread of respiratory pathogens, less attention has been given to modeling the interdependence of disease introduction and spread seen in congregate settings, such as prisons or nursing homes. As demonstrated by the explosive outbreaks of COVID-19 seen in congregate settings, the need for effective outbreak prevention and mitigation strategies for these settings is critical. Here we consider how interventions that decrease the size of the susceptible populations, such as vaccination or depopulation, impact the expected number of infections due to outbreaks. Introduction of disease into the resident population from the community is modeled as a branching process, while spread between residents is modeled via a compartmental model. Control is modeled as a proportional decrease in both the number of susceptible residents and the reproduction number. We find that vaccination or depopulation can have a greater than linear effect on anticipated infections. For example, assuming a reproduction number of 3.0 for density-dependent COVID-19 transmission, we find that reducing the size of the susceptible population by 20% reduced overall disease burden by 47%. We highlight the California state prison system as an example for how these findings provide a quantitative framework for implementing infection control in congregate settings. Additional applications of our modeling framework include optimizing the distribution of residents into independent residential units, and comparison of preemptive versus reactive vaccination strategies.
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Affiliation(s)
- Seth Blumberg
- University of California San Francisco, Francis I. Proctor Foundation, San Francisco, California, USA
- CDC MInD Healthcare Program
- University of California San Francisco, Department of Medicine, San Francisco, California, USA
| | - Phoebe Lu
- University of California San Francisco, Francis I. Proctor Foundation, San Francisco, California, USA
- CDC MInD Healthcare Program
| | - Christopher M. Hoover
- University of California San Francisco, Francis I. Proctor Foundation, San Francisco, California, USA
- CDC MInD Healthcare Program
| | - James O. Lloyd-Smith
- University of California Los Angeles, Department of Ecology and Evolutionary Biology, Los Angeles, California, USA
| | - Ada T. Kwan
- University of California San Francisco, Department of Medicine, San Francisco, California, USA
| | - David Sears
- University of California San Francisco, Department of Medicine, San Francisco, California, USA
| | - Stefano M. Bertozzi
- University of California, Berkeley, California, USA
- University of Washington, Seattle, Washington, USA
- National Institute of Public Health, Mexico, Cuernavaca, Mexico
| | - Lee Worden
- University of California San Francisco, Francis I. Proctor Foundation, San Francisco, California, USA
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267
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Ho CK. Modeling airborne pathogen transport and transmission risks of SARS-CoV-2. APPLIED MATHEMATICAL MODELLING 2021; 95:297-319. [PMID: 33642664 PMCID: PMC7902220 DOI: 10.1016/j.apm.2021.02.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 02/01/2021] [Accepted: 02/14/2021] [Indexed: 05/06/2023]
Abstract
An integrated modeling approach has been developed to better understand the relative impacts of different expiratory and environmental factors on airborne pathogen transport and transmission, motivated by the recent COVID-19 pandemic. Computational fluid dynamics (CFD) modeling was used to simulate spatial-temporal aerosol concentrations and quantified risks of exposure as a function of separation distance, exposure duration, environmental conditions (e.g., airflow/ventilation), and face coverings. The CFD results were combined with infectivity models to determine probability of infection, which is a function of the spatial-temporal aerosol concentrations, viral load, infectivity rate, viral viability, lung-deposition probability, and inhalation rate. Uncertainty distributions were determined for these parameters from the literature. Probabilistic analyses were performed to determine cumulative distributions of infection probabilities and to determine the most important parameters impacting transmission. This modeling approach has relevance to both pathogen and pollutant dispersion from expelled aerosol plumes.
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Affiliation(s)
- Clifford K Ho
- Sandia National Laboratories, P.O. Box 5800, MS-1127, Albuquerque, NM 87185, USA
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268
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Xu P, Jia W, Qian H, Xiao S, Miao T, Yen HL, Tan H, Kang M, Cowling BJ, Li Y. Lack of cross-transmission of SARS-CoV-2 between passenger's cabins on the Diamond Princess cruise ship. BUILDING AND ENVIRONMENT 2021; 198:107839. [PMID: 33875902 PMCID: PMC8046742 DOI: 10.1016/j.buildenv.2021.107839] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 02/28/2021] [Accepted: 03/22/2021] [Indexed: 05/07/2023]
Abstract
An outbreak of COVID-19 occurred on the Diamond Princess cruise ship in January and February 2020 in Japan. We analysed information on the cases of infection to infer whether airborne transmission of SARS-CoV-2, the causative agent of COVID-19, had occurred between cabins. We infer from our analysis that most infections in passengers started on 28 January and were completed by 6 February, except in those who shared a cabin with another infected passenger. The distribution of the infected cabins was random, and no spatial cluster of the infected can be identified. We infer that the ship's central air-conditioning system for passenger's cabins did not play a role in SARS-CoV-2 transmission, i.e. airborne transmission did not occur between cabins during the outbreak, suggesting that the sufficient ventilation was provided. We also infer that the ship's cabin drainage system did not play a role. Most transmission appears to have occurred in the public areas of the cruise ship, likely due to crowding and insufficient ventilation in some of these areas.
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Affiliation(s)
- Pengcheng Xu
- Institute of Applied Mathematics, Academy of Mathematics and Systems Sciences, Chinese Academy of Sciences, Beijing, China
| | - Wei Jia
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 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
| | - Te Miao
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
| | - Hui-Ling Yen
- School of Public Health, The University of Hong Kong, Hong Kong, China
| | - Hongwei Tan
- School of Mechanical and Energy Engineering, Tongji University, Shanghai, China
| | - Min Kang
- Guangdong Provincial Center for Disease Control and Prevention, Guangzhou, 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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269
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Li Y. Hypothesis: SARS-CoV-2 transmission is predominated by the short-range airborne route and exacerbated by poor ventilation. INDOOR AIR 2021; 31:921-925. [PMID: 34002888 PMCID: PMC8242709 DOI: 10.1111/ina.12837] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 03/13/2021] [Accepted: 03/24/2021] [Indexed: 05/07/2023]
Affiliation(s)
- Yuguo Li
- Department of Mechanical EngineeringThe University of Hong KongHong KongChina
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270
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Schramm MWJ, Sheikh AJ, Chave-Cox R, McQuaid J, Whitty RCW, Ilyinskaya E. Surgically generated aerosol and mitigation strategies: combined use of irrigation, respirators and suction massively reduces particulate matter aerosol. Acta Neurochir (Wien) 2021; 163:1819-1827. [PMID: 34031774 PMCID: PMC8143442 DOI: 10.1007/s00701-021-04874-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 05/09/2021] [Indexed: 11/14/2022]
Abstract
Background Aerosol is a health risk to theatre staff. This laboratory study quantifies the reduction in particulate matter aerosol concentrations produced by electrocautery and drilling when using mitigation strategies such as irrigation, respirator filtration and suction in a lab environment to prepare for future work under live OR conditions. Methods We combined one aerosol-generating procedure (monopolar cutting or coagulating diathermy or high-speed diamond- or steel-tipped drilling of cadaveric porcine tissue) with one or multiple mitigation strategies (instrument irrigation, plume suction and filtration using an FFP3 respirator filter) and using an optical particle counter to measure particulate matter aerosol size and concentrations. Results Significant aerosol concentrations were observed during all aerosol-generating procedures with concentrations exceeding 3 × 106 particles per 100 ml. Considerable reductions in concentrations were observed with mitigation. In drilling, suction, FFP3 filtration and wash alone respectively reduced aerosol by 19.3–31.6%, 65.1–70.8% and 97.2 to > 99.9%. The greatest reduction (97.38 to > 99.9%) was observed when combining irrigation and filtration. Coagulating diathermy reduced concentrations by 88.0–96.6% relative to cutting, but produced larger particles. Suction alone, and suction with filtration reduced aerosol concentration by 41.0–49.6% and 88.9–97.4% respectively. No tested mitigation strategies returned aerosol concentrations to baseline. Conclusion Aerosol concentrations are significantly reduced through the combined use of filtration, suction and irrigation. Further research is required to characterise aerosol concentrations in the live OR and to find acceptable exposure limits, and in their absence, to find methods to further reduce exposure to theatre staff.
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271
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Vouriot CVM, Burridge HC, Noakes CJ, Linden PF. Seasonal variation in airborne infection risk in schools due to changes in ventilation inferred from monitored carbon dioxide. INDOOR AIR 2021; 31:1154-1163. [PMID: 33682974 DOI: 10.1177/1420326x211043564] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 02/23/2021] [Accepted: 02/24/2021] [Indexed: 05/27/2023]
Abstract
The year 2020 has seen the world gripped by the effects of the COVID-19 pandemic. It is not the first time, nor will it be last, that our increasingly globalized world has been significantly affected by the emergence of a new disease. In much of the Northern Hemisphere, the academic year begins in September, and for many countries, September 2020 marked the return to full schooling after some period of enforced closure due to COVID-19. In this paper, we focus on the airborne spread of disease and investigate the likelihood of transmission in school environments. It is crucial to understand the risk airborne infection from COVID-19 might pose to pupils, teachers, and their wider social groups. We use monitored CO2 data from 45 classrooms in 11 different schools from within the UK to estimate the likelihood of infection occurring within classrooms regularly attended by the same staff and pupils. We determine estimates of the number of secondary infections arising via the airborne route over pre/asymptomatic periods on a rolling basis. Results show that, assuming relatively quiet desk-based work, the number of secondary infections is likely to remain reassuringly below unity; however, it can vary widely between classrooms of the same school even when the same ventilation system is present. Crucially, the data highlight significant variation with the seasons with January being nearly twice as risky as July. We show that such seasonal variations in risk due to changes in ventilation rates are robust and our results hold for wide variations in disease parameterizations, suggesting our results may be applied to a number of different airborne diseases.
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Affiliation(s)
- Carolanne V M Vouriot
- Department of Civil and Environmental Engineering, Imperial College London, London, UK
| | - Henry C Burridge
- Department of Civil and Environmental Engineering, Imperial College London, London, UK
| | - Catherine J Noakes
- School of Civil Engineering, Woodhouse Lane, University of Leeds, Leeds, UK
| | - Paul F Linden
- Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Cambridge, UK
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272
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Vouriot CVM, Burridge HC, Noakes CJ, Linden PF. Seasonal variation in airborne infection risk in schools due to changes in ventilation inferred from monitored carbon dioxide. INDOOR AIR 2021; 31:1154-1163. [PMID: 33682974 PMCID: PMC8251097 DOI: 10.1111/ina.12818] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 02/23/2021] [Accepted: 02/24/2021] [Indexed: 05/05/2023]
Abstract
The year 2020 has seen the world gripped by the effects of the COVID-19 pandemic. It is not the first time, nor will it be last, that our increasingly globalized world has been significantly affected by the emergence of a new disease. In much of the Northern Hemisphere, the academic year begins in September, and for many countries, September 2020 marked the return to full schooling after some period of enforced closure due to COVID-19. In this paper, we focus on the airborne spread of disease and investigate the likelihood of transmission in school environments. It is crucial to understand the risk airborne infection from COVID-19 might pose to pupils, teachers, and their wider social groups. We use monitored CO2 data from 45 classrooms in 11 different schools from within the UK to estimate the likelihood of infection occurring within classrooms regularly attended by the same staff and pupils. We determine estimates of the number of secondary infections arising via the airborne route over pre/asymptomatic periods on a rolling basis. Results show that, assuming relatively quiet desk-based work, the number of secondary infections is likely to remain reassuringly below unity; however, it can vary widely between classrooms of the same school even when the same ventilation system is present. Crucially, the data highlight significant variation with the seasons with January being nearly twice as risky as July. We show that such seasonal variations in risk due to changes in ventilation rates are robust and our results hold for wide variations in disease parameterizations, suggesting our results may be applied to a number of different airborne diseases.
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Affiliation(s)
| | - Henry C. Burridge
- Department of Civil and Environmental EngineeringImperial College LondonLondonUK
| | | | - Paul F. Linden
- Department of Applied Mathematics and Theoretical PhysicsCentre for Mathematical SciencesUniversity of CambridgeCambridgeUK
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273
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Wilson AM, Jones RM, Lugo Lerma V, Abney SE, King MF, Weir MH, Sexton JD, Noakes CJ, Reynolds KA. Respirators, face masks, and their risk reductions via multiple transmission routes for first responders within an ambulance. JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 2021; 18:345-360. [PMID: 34129448 DOI: 10.1080/15459624.2021.1926468] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
First responders may have high SARS-CoV-2 infection risks due to working with potentially infected patients in enclosed spaces. The study objective was to estimate infection risks per transport for first responders and quantify how first responder use of N95 respirators and patient use of cloth masks can reduce these risks. A model was developed for two Scenarios: an ambulance transport with a patient actively emitting a virus in small aerosols that could lead to airborne transmission (Scenario 1) and a subsequent transport with the same respirator or mask use conditions, an uninfected patient; and remaining airborne SARS-CoV-2 and contaminated surfaces due to aerosol deposition from the previous transport (Scenario 2). A compartmental Monte Carlo simulation model was used to estimate the dispersion and deposition of SARS-CoV-2 and subsequent infection risks for first responders, accounting for variability and uncertainty in input parameters (i.e., transport duration, transfer efficiencies, SARS-CoV-2 emission rates from infected patients, etc.). Infection risk distributions and changes in concentration on hands and surfaces over time were estimated across sub-Scenarios of first responder respirator use and patient cloth mask use. For Scenario 1, predicted mean infection risks were reduced by 69%, 48%, and 85% from a baseline risk (no respirators or face masks used) of 2.9 × 10-2 ± 3.4 × 10-2 when simulated first responders wore respirators, the patient wore a cloth mask, and when first responders and the patient wore respirators or a cloth mask, respectively. For Scenario 2, infection risk reductions for these same Scenarios were 69%, 50%, and 85%, respectively (baseline risk of 7.2 × 10-3 ± 1.0 × 10-2). While aerosol transmission routes contributed more to viral dose in Scenario 1, our simulations demonstrate the ability of face masks worn by patients to additionally reduce surface transmission by reducing viral deposition on surfaces. Based on these simulations, we recommend the patient wear a face mask and first responders wear respirators, when possible, and disinfection should prioritize high use equipment.
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Affiliation(s)
- Amanda M Wilson
- Rocky Mountain Center for Occupational and Environmental Health, University of Utah, Salt Lake City, Utah
- Department of Family and Preventive Medicine, School of Medicine, University of Utah, Salt Lake City, Utah
| | - Rachael M Jones
- Rocky Mountain Center for Occupational and Environmental Health, University of Utah, Salt Lake City, Utah
- Department of Family and Preventive Medicine, School of Medicine, University of Utah, Salt Lake City, Utah
| | - Veronica Lugo Lerma
- Department of Community, Environment, and Policy, Mel and Enid Zuckerman College of Public Health, University of Arizona, Tucson, Arizona
| | - Sarah E Abney
- Department of Community, Environment, and Policy, Mel and Enid Zuckerman College of Public Health, University of Arizona, Tucson, Arizona
- Department of Environmental Science, College of Agriculture and Life Sciences, University of Arizona, Tucson, Arizona
| | | | - Mark H Weir
- Divison of Environmental Health Sciences, College of Public Health, The Ohio State University, Columbus, Ohio
| | - Jonathan D Sexton
- Department of Community, Environment, and Policy, Mel and Enid Zuckerman College of Public Health, University of Arizona, Tucson, Arizona
| | | | - Kelly A Reynolds
- Department of Community, Environment, and Policy, Mel and Enid Zuckerman College of Public Health, University of Arizona, Tucson, Arizona
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274
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Ram K, Thakur RC, Singh DK, Kawamura K, Shimouchi A, Sekine Y, Nishimura H, Singh SK, Pavuluri CM, Singh RS, Tripathi SN. Why airborne transmission hasn't been conclusive in case of COVID-19? An atmospheric science perspective. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 773:145525. [PMID: 33940729 PMCID: PMC7984961 DOI: 10.1016/j.scitotenv.2021.145525] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 01/15/2021] [Accepted: 01/26/2021] [Indexed: 05/06/2023]
Abstract
Airborne transmission is one of the routes for the spread of COVID-19 which is caused by inhalation of smaller droplets1 containing SARS-CoV-2 (i.e., either virus-laden particulate matter: PM and/or droplet nuclei) in an indoor environment. Notably, a significant fraction of the small droplets, along with respiratory droplets, is produced by both symptomatic and asymptomatic individuals during expiratory events such as breathing, sneezing, coughing and speaking. When these small droplets are exposed to the ambient environment, they may interact with PM and may remain suspended in the atmosphere even for several hours. Therefore, it is important to know the fate of these droplets and processes (e.g., physical and chemical) in the atmosphere to better understand airborne transmission. Therefore, we reviewed existing literature focussed on the transmission of SARS-CoV-2 in the spread of COVID-19 and present an environmental perspective on why airborne transmission hasn't been very conclusive so far. In addition, we discuss various environmental factors (e.g., temperature, humidity, etc.) and sampling difficulties, which affect the conclusions of the studies focussed on airborne transmission. One of the reasons for reduced emphasis on airborne transmission could be that the smaller droplets have less number of viruses as compared to larger droplets. Further, smaller droplets can evaporate faster, exposing SARS-CoV-2 within the small droplets to the environment, whose viability may further reduce. For example, these small droplets containing SARS-CoV-2 might also physically combine with or attach to pre-existing PM so that their behaviour and fate may be governed by PM composition. Thus, the measurement of their infectivity and viability is highly uncertain due to a lack of robust sampling system to separately collect virions in the atmosphere. We believe that the present review will help to minimize the gap in our understanding of the current pandemic and develop a robust epidemiological method for mortality assessment.
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Affiliation(s)
- Kirpa Ram
- Institute of Environment and Sustainable Development, Banaras Hindu University, Varanasi 221005, India.
| | - Roseline C Thakur
- Institute for Atmospheric and Earth System Research (INAR)/Physics, Faculty of Science, University of Helsinki, 00014 Helsinki, Finland.
| | - Dharmendra Kumar Singh
- French National Centre for Scientific Research (CNRS)/IRCE Lyon, 2 avenue Albert Einstein, Villeurbanne 69100, France.
| | - Kimitaka Kawamura
- Chubu Institute for Advanced Studies, Chubu University, Kasugai 487-8501, Japan.
| | - Akito Shimouchi
- School of Life and Health Sciences, Chubu University, Kasugai 487-8501, Japan.
| | - Yoshika Sekine
- Department of Chemistry, Tokai University, Hiratsuka, Kanagawa 25901292, Japan.
| | - Hidekazu Nishimura
- Virus Research Center, Clinical Research Division, Sendai Medical Center, Sendai, Japan.
| | - Sunit K Singh
- Laboratory of Molecular Virology & Immunology, Molecular Biology Unit, Faculty of Medicine, Institute of Medical Sciences (IMS), Banaras Hindu University (BHU), Varanasi 221005, India.
| | - Chandra Mouli Pavuluri
- Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China.
| | - R S Singh
- Department of Chemical Engineering, IIT (BHU), Varanasi 221005, Uttar Pradesh, India.
| | - S N Tripathi
- Department of Civil Engineering, Centre for Environmental Science and Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India.
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275
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Corrêa TQ, Blanco KC, Vollet-Filho JD, Morais VS, Trevelin WR, Pratavieira S, Bagnato VS. Efficiency of an air circulation decontamination device for micro-organisms using ultraviolet radiation. J Hosp Infect 2021; 115:32-43. [PMID: 34126104 DOI: 10.1016/j.jhin.2021.06.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 05/31/2021] [Accepted: 06/03/2021] [Indexed: 12/23/2022]
Abstract
BACKGROUND The concern with environmental security to avoid contamination of individuals was intensified with the crisis established by SARS-CoV-2. The COVID-19 pandemic has shown the necessity to create systems and devices capable of clearing the air in an environment of micro-organisms more efficiently. The development of systems that allow the removal of micro-droplets mainly originating from breathing or talking from the air was the motivation of this study. AIM This article describes a portable and easy-to-operate system that helps to eliminate the droplets or aerosols present in the environment by circulating air through an ultraviolet-C (UV-C) reactor. METHODS An air circulation device was developed, and a proof-of-principle study was performed using the device against bacteria in simulated and natural environments. The microbiological analysis was carried out by the simple sedimentation technique. In order to compare the experimental results and the expected results for other micro-organisms, the reduction rate values for bacteria and viruses were calculated and compared with the experimental results based on technical parameters (clean air delivery rate (CADR) and air changes per hour (ACH)). FINDINGS Results showed that the micro-organisms were eliminated with high efficiency by the air circulation decontamination device, with reductions of 99.9% in the proof-of-principle study, and 84-97% in the hospital environments study, contributing to reducing contamination of individuals in environments considered to present risk. CONCLUSION This study resulted in a low-cost and relatively simple device, which was shown to be effective and safe, and could be replicated, especially in low-income countries, respecting the standards for air disinfection using UV-C technologies.
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Affiliation(s)
- T Q Corrêa
- São Carlos Institute of Physics, University of São Paulo, São Carlos, São Paulo, Brazil.
| | - K C Blanco
- São Carlos Institute of Physics, University of São Paulo, São Carlos, São Paulo, Brazil
| | - J D Vollet-Filho
- São Carlos Institute of Physics, University of São Paulo, São Carlos, São Paulo, Brazil
| | - V S Morais
- São Carlos Institute of Physics, University of São Paulo, São Carlos, São Paulo, Brazil
| | | | - S Pratavieira
- São Carlos Institute of Physics, University of São Paulo, São Carlos, São Paulo, Brazil
| | - V S Bagnato
- São Carlos Institute of Physics, University of São Paulo, São Carlos, São Paulo, Brazil; Texas A&M University, College Station, TX, USA
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276
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Hyde Z, Berger D, Miller A. Australia must act to prevent airborne transmission of SARS-CoV-2. Med J Aust 2021; 215:7-9.e1. [PMID: 34131921 PMCID: PMC8447137 DOI: 10.5694/mja2.51131] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 04/20/2021] [Accepted: 04/20/2021] [Indexed: 12/19/2022]
Affiliation(s)
- Zoë Hyde
- WA Centre for Health and Ageing, University of Western Australia, Perth, WA
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277
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Pease LF, Wang N, Salsbury TI, Underhill RM, Flaherty JE, Vlachokostas A, Kulkarni G, James DP. Investigation of potential aerosol transmission and infectivity of SARS-CoV-2 through central ventilation systems. BUILDING AND ENVIRONMENT 2021; 197:107633. [PMID: 33531734 PMCID: PMC7844370 DOI: 10.1016/j.buildenv.2021.107633] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 12/23/2020] [Accepted: 01/15/2021] [Indexed: 05/18/2023]
Abstract
The COVID-19 pandemic has raised concern of viral spread within buildings. Although near-field transmission and infectious spread within individual rooms are well studied, the impact of aerosolized spread of SARS-CoV-2 via air handling systems within multiroom buildings remains unexplored. This study evaluates the concentrations and probabilities of infection for both building interior and exterior exposure sources using a well-mixed model in a multiroom building served by a central air handling system (without packaged terminal air conditioning). In particular, we compare the influence of filtration, air change rates, and the fraction of outdoor air. When the air supplied to the rooms comprises both outdoor air and recirculated air, we find filtration lowers the concentration and probability of infection the most in connected rooms. We find that increasing the air change rate removes virus from the source room faster but also increases the rate of exposure in connected rooms. Therefore, slower air change rates reduce infectivity in connected rooms at shorter durations. We further find that increasing the fraction of virus-free outdoor air is helpful, unless outdoor air is infective in which case pathogen exposure inside persists for hours after a short-term release. Increasing the outdoor air to 33% or the filter to MERV-13 decreases the infectivity in the connected rooms by 19% or 93% respectively, relative to a MERV-8 filter with 9% outdoor air based on 100 quanta/h of 5 μm droplets, a breathing rate of 0.48 m3/h, and the building dimensions and air handling system considered.
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Affiliation(s)
- Leonard F Pease
- 902 Battelle Boulevard, P.O. Box 999, MSIN K9-89, Pacific Northwest National Laboratory (PNNL), Richland, WA, 99352, USA
| | - Na Wang
- 902 Battelle Boulevard, P.O. Box 999, MSIN K9-89, Pacific Northwest National Laboratory (PNNL), Richland, WA, 99352, USA
| | - Timothy I Salsbury
- 902 Battelle Boulevard, P.O. Box 999, MSIN K9-89, Pacific Northwest National Laboratory (PNNL), Richland, WA, 99352, USA
| | - Ronald M Underhill
- 902 Battelle Boulevard, P.O. Box 999, MSIN K9-89, Pacific Northwest National Laboratory (PNNL), Richland, WA, 99352, USA
| | - Julia E Flaherty
- 902 Battelle Boulevard, P.O. Box 999, MSIN K9-89, Pacific Northwest National Laboratory (PNNL), Richland, WA, 99352, USA
| | - Alex Vlachokostas
- 902 Battelle Boulevard, P.O. Box 999, MSIN K9-89, Pacific Northwest National Laboratory (PNNL), Richland, WA, 99352, USA
| | - Gourihar Kulkarni
- 902 Battelle Boulevard, P.O. Box 999, MSIN K9-89, Pacific Northwest National Laboratory (PNNL), Richland, WA, 99352, USA
| | - Daniel P James
- 902 Battelle Boulevard, P.O. Box 999, MSIN K9-89, Pacific Northwest National Laboratory (PNNL), Richland, WA, 99352, USA
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278
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Drossinos Y, Weber TP, Stilianakis NI. Droplets and aerosols: An artificial dichotomy in respiratory virus transmission. Health Sci Rep 2021; 4:e275. [PMID: 33977157 PMCID: PMC8103093 DOI: 10.1002/hsr2.275] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 02/08/2021] [Accepted: 03/16/2021] [Indexed: 12/13/2022] Open
Abstract
In the medical literature, three mutually non-exclusive modes of pathogen transmission associated with respiratory droplets are usually identified: contact, droplet, and airborne (or aerosol) transmission. The demarcation between droplet and airborne transmission is often based on a cut-off droplet diameter, most commonly 5 μm. We argue here that the infectivity of a droplet, and consequently the transmissivity of the virus, as a function of droplet size is a continuum, depending on numerous factors (gravitational settling rate, transport, and dispersion in a turbulent air jet, viral load and viral shedding, virus inactivation) that cannot be adequately characterized by a single droplet diameter. We propose instead that droplet and aerosol transmission should be replaced by a unique airborne transmission mode, to be distinguished from contact transmission.
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Affiliation(s)
- Yannis Drossinos
- Joint Research CentreEuropean Commission, Joint Research Centre (JRC)IspraItaly
| | - Thomas P. Weber
- Joint Research CentreEuropean Commission, Directorate General for Health and Food SafetyBrusselsBelgium
| | - Nikolaos I. Stilianakis
- Joint Research CentreEuropean Commission, Joint Research Centre (JRC)IspraItaly
- Department of Biometry and EpidemiologyUniversity of Erlangen‐NurembergErlangenGermany
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279
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Li Y, Qian H, Hang J, Chen X, Cheng P, Ling H, Wang S, Liang P, Li J, Xiao S, Wei J, Liu L, Cowling BJ, Kang M. Probable airborne transmission of SARS-CoV-2 in a poorly ventilated restaurant. BUILDING AND ENVIRONMENT 2021; 196:107788. [PMID: 33746341 PMCID: PMC7954773 DOI: 10.1016/j.buildenv.2021.107788] [Citation(s) in RCA: 224] [Impact Index Per Article: 74.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 03/05/2021] [Accepted: 03/06/2021] [Indexed: 05/02/2023]
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.
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Affiliation(s)
- 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
| | - Hua Qian
- School of Energy and Environment, Southeast University, Nanjing, China
| | - Jian Hang
- School of Atmospheric Sciences, Sun Yat-sen University and Key Laboratory of Tropical Atmosphere-Ocean System, Ministry of Education, Zhuhai, China
| | - Xuguang Chen
- Guangdong Provincial Center for Disease Control and Prevention, Guangzhou, China
| | - Pan Cheng
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
| | - Hong Ling
- School of Atmospheric Sciences, Sun Yat-sen University and Key Laboratory of Tropical Atmosphere-Ocean System, Ministry of Education, Zhuhai, China
| | - Shengqi Wang
- School of Energy and Environment, Southeast University, Nanjing, China
| | - Peng Liang
- Guangdong Field Epidemiology Training Program, Ganzi Tibetan Autonomous Prefecture Center for Disease Control and Prevention, Sichuan, China
| | - Jiansen Li
- Guangdong Provincial Center for Disease Control and Prevention, Guangzhou, China
| | - Shenglan Xiao
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
- School of Public Health, Sun Yat-sen University, Shenzhen, China
| | - Jianjian Wei
- Institute of Refrigeration and Cryogenics and Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Zhejiang University, Hangzhou, China
| | - Li Liu
- School of Architecture, Tsinghua University, Beijing, China
| | | | - Min Kang
- Guangdong Provincial Center for Disease Control and Prevention, Guangzhou, China
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280
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Villanueva F, Notario A, Cabañas B, Martín P, Salgado S, Gabriel MF. Assessment of CO 2 and aerosol (PM 2.5, PM 10, UFP) concentrations during the reopening of schools in the COVID-19 pandemic: The case of a metropolitan area in Central-Southern Spain. ENVIRONMENTAL RESEARCH 2021; 197:111092. [PMID: 33785326 PMCID: PMC8003457 DOI: 10.1016/j.envres.2021.111092] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 02/25/2021] [Accepted: 03/24/2021] [Indexed: 05/05/2023]
Abstract
Public health authorities have been paramount in guaranteeing that adequate fresh air ventilation is promoted in classrooms to avoid SARS-CoV-2 transmission in educational environments. In this work it was aimed to assess ventilation conditions (carbon dioxide, CO2) and suspended particulate matter (PM2.5, PM10 and UFP) levels in 19 classrooms - including preschool, primary and secondary education - located in the metropolitan area of Ciudad Real, Central-Southern Spain, during the school's reopening (from September 30th until October 27th, 2020) after about 7 months of lockdown due to COVID-19 pandemic. The classrooms that presented the worst indoor environmental conditions, according to the highest peak of concentration obtained, were particularly explored to identify the possible influencing factors and respective opportunities for improvement. Briefly, findings suggested that although ventilation promoted through opening windows and doors according to official recommendations is guaranteeing adequate ventilation conditions in most of the studied classrooms, thus minimizing the risk of SARS-CoV-2 airborne transmission, a total of 5 (26%) surveyed classrooms were found to exceed the recommended CO2 concentration limit value (700 ppm). In general, preschool rooms were the educational environments that registered better ventilation conditions, while secondary classrooms exhibited the highest peak and average CO2 concentrations. In turn, for PM2.5, PM10 and UFP, the concentrations assessed in preschools were, on average about 2-fold greater than the levels obtained in both primary and secondary classrooms. In fact, the indoor PM2.5 and PM10 concentrations substantially exceeded the recommended limits of 8hr-exposure, established by WHO, in 63% and 32% of the surveyed classrooms, respectively. Overall, it is expected that the findings presented in this study will assist the establishment of evidence-based measures (namely based on ensuring proper ventilation rates and air filtration) to mitigate preventable environmental harm in public school buildings, mainly at local and national levels.
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Affiliation(s)
- Florentina Villanueva
- Universidad de Castilla La Mancha, Instituto de Investigación en Combustión y Contaminación Atmosférica, Camino de Moledores s/n, 13071, Ciudad Real, Spain; Parque Científico y Tecnológico de Castilla La Mancha, Paseo de la Innovación 1, 02006, Albacete, Spain
| | - Alberto Notario
- Universidad de Castilla La Mancha, Instituto de Investigación en Combustión y Contaminación Atmosférica, Camino de Moledores s/n, 13071, Ciudad Real, Spain; Universidad de Castilla La Mancha, Departamento de Química Física, Facultad de Ciencias y Tecnologías Químicas, Avenida Camilo José Cela s/n, 13071, Ciudad Real, Spain
| | - Beatriz Cabañas
- Universidad de Castilla La Mancha, Instituto de Investigación en Combustión y Contaminación Atmosférica, Camino de Moledores s/n, 13071, Ciudad Real, Spain; Universidad de Castilla La Mancha, Departamento de Química Física, Facultad de Ciencias y Tecnologías Químicas, Avenida Camilo José Cela s/n, 13071, Ciudad Real, Spain
| | - Pilar Martín
- Universidad de Castilla La Mancha, Instituto de Investigación en Combustión y Contaminación Atmosférica, Camino de Moledores s/n, 13071, Ciudad Real, Spain; Universidad de Castilla La Mancha, Departamento de Química Física, Facultad de Ciencias y Tecnologías Químicas, Avenida Camilo José Cela s/n, 13071, Ciudad Real, Spain
| | - Sagrario Salgado
- Universidad de Castilla La Mancha, Instituto de Investigación en Combustión y Contaminación Atmosférica, Camino de Moledores s/n, 13071, Ciudad Real, Spain; Universidad de Castilla La Mancha, Departamento de Química Física, Facultad de Ciencias y Tecnologías Químicas, Avenida Camilo José Cela s/n, 13071, Ciudad Real, Spain
| | - Marta Fonseca Gabriel
- INEGI, Institute of Science and Innovation in Mechanical and Industrial Engineering, Campus da FEUP, Rua Dr. Roberto Frias 400, 4200-465, Porto, Portugal.
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281
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Cook JD, Grant EHC, Coleman JTH, Sleeman JM, Runge MC. Risks posed by SARS-CoV-2 to North American bats during winter fieldwork. CONSERVATION SCIENCE AND PRACTICE 2021; 3:e410. [PMID: 34230913 PMCID: PMC8250205 DOI: 10.1111/csp2.410] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 03/09/2021] [Accepted: 03/11/2021] [Indexed: 12/15/2022] Open
Abstract
The virus that causes COVID-19 likely evolved in a mammalian host, possibly Old-World bats, before adapting to humans, raising the question of whether reverse zoonotic transmission to bats is possible. Wildlife management agencies in North America are concerned that the activities they authorize could lead to transmission of SARS-CoV-2 to bats from humans. A rapid risk assessment conducted in April 2020 suggested that there was a small but significant possibility that SARS-CoV-2 could be transmitted from humans to bats during summer fieldwork, absent precautions. Subsequent challenge studies in a laboratory setting have shed new information on these risks, as has more detailed information on human epidemiology and transmission. This inquiry focuses on the risk to bats from winter fieldwork, specifically surveys of winter roosts and handling of bats to test for white-nose syndrome or other research needs. We use an aerosol transmission model, with parameter estimates both from the literature and from formal expert judgment, to estimate the risk to three species of North American bats, as a function of several factors. We find that risks of transmission are lower than in the previous assessment and are notably affected by chamber volume and local prevalence of COVID-19. Use of facemasks with high filtration efficiency or a negative COVID-19 test before field surveys can reduce zoonotic risk by 65 to 88%.
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Affiliation(s)
- Jonathan D. Cook
- U.S. Geological SurveyPatuxent Wildlife Research CenterLaurelMarylandUSA
| | - Evan H. C. Grant
- U.S. Geological SurveyPatuxent Wildlife Research CenterTurner's FallsMassachusettsUSA
| | | | | | - Michael C. Runge
- U.S. Geological SurveyPatuxent Wildlife Research CenterLaurelMarylandUSA
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282
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Li Y, Qian H, Hang J, Chen X, Cheng P, Ling H, Wang S, Liang P, Li J, Xiao S, Wei J, Liu L, Cowling BJ, Kang M. Probable airborne transmission of SARS-CoV-2 in a poorly ventilated restaurant. BUILDING AND ENVIRONMENT 2021; 196:107788. [PMID: 33746341 DOI: 10.1101/2020.04.16.20067728] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 03/05/2021] [Accepted: 03/06/2021] [Indexed: 05/22/2023]
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.
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Affiliation(s)
- 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
| | - Hua Qian
- School of Energy and Environment, Southeast University, Nanjing, China
| | - Jian Hang
- School of Atmospheric Sciences, Sun Yat-sen University and Key Laboratory of Tropical Atmosphere-Ocean System, Ministry of Education, Zhuhai, China
| | - Xuguang Chen
- Guangdong Provincial Center for Disease Control and Prevention, Guangzhou, China
| | - Pan Cheng
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
| | - Hong Ling
- School of Atmospheric Sciences, Sun Yat-sen University and Key Laboratory of Tropical Atmosphere-Ocean System, Ministry of Education, Zhuhai, China
| | - Shengqi Wang
- School of Energy and Environment, Southeast University, Nanjing, China
| | - Peng Liang
- Guangdong Field Epidemiology Training Program, Ganzi Tibetan Autonomous Prefecture Center for Disease Control and Prevention, Sichuan, China
| | - Jiansen Li
- Guangdong Provincial Center for Disease Control and Prevention, Guangzhou, China
| | - Shenglan Xiao
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
- School of Public Health, Sun Yat-sen University, Shenzhen, China
| | - Jianjian Wei
- Institute of Refrigeration and Cryogenics and Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Zhejiang University, Hangzhou, China
| | - Li Liu
- School of Architecture, Tsinghua University, Beijing, China
| | | | - Min Kang
- Guangdong Provincial Center for Disease Control and Prevention, Guangzhou, China
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283
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Ji B, Zhao Y, Esteve-Núñez A, Liu R, Yang Y, Nzihou A, Tai Y, Wei T, Shen C, Yang Y, Ren B, Wang X, Wang Y. Where do we stand to oversee the coronaviruses in aqueous and aerosol environment? Characteristics of transmission and possible curb strategies. CHEMICAL ENGINEERING JOURNAL (LAUSANNE, SWITZERLAND : 1996) 2021; 413:127522. [PMID: 33132743 PMCID: PMC7590645 DOI: 10.1016/j.cej.2020.127522] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Revised: 10/20/2020] [Accepted: 10/23/2020] [Indexed: 05/08/2023]
Abstract
By 17 October 2020, the severe acute respiratory syndrome coronavirus (SARS-CoV-2) has caused confirmed infection of more than 39,000,000 people in 217 countries and territories globally and still continues to grow. As environmental professionals, understanding how SARS-CoV-2 can be transmitted via water and air environment is a concern. We have to be ready for focusing our attention to the prompt diagnosis and potential infection control procedures of the virus in integrated water and air system. This paper reviews the state-of-the-art information from available sources of published papers, newsletters and large number of scientific websites aimed to provide a comprehensive profile on the transmission characteristics of the coronaviruses in water, sludge, and air environment, especially the water and wastewater treatment systems. The review also focused on proposing the possible curb strategies to monitor and eventually cut off the coronaviruses under the authors' knowledge and understanding.
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Affiliation(s)
- Bin Ji
- Department of Municipal and Environmental Engineering, Faculty of Water Resources and Hydroelectric Engineering, Xi'an University of Technology, Xi'an 710048, PR China
- State Key Laboratory of Eco-Hydraulics in Northwest Arid Region, Xi'an University of Technology, Xi'an 710048, PR China
| | - Yaqian Zhao
- Department of Municipal and Environmental Engineering, Faculty of Water Resources and Hydroelectric Engineering, Xi'an University of Technology, Xi'an 710048, PR China
- State Key Laboratory of Eco-Hydraulics in Northwest Arid Region, Xi'an University of Technology, Xi'an 710048, PR China
- Dooge Centre for Water Resources Research, School of Civil Engineering, University College Dublin, Belfield, Dublin 4, Ireland
| | | | - Ranbin Liu
- Sino-Dutch R&D Centre for Future Wastewater Treatment Technologies/Beijing Advanced Innovation Center of Future Urban Design, Beijing University of Civil Engineering & Architecture, Beijing 100044, PR China
| | - Yang Yang
- Institute of Hydrobiology, Jinan University, Guangzhou 510632, PR China
- Engineering Research Center of Tropical and Subtropical Aquatic Ecological Engineering, Ministry of Education, Guangzhou, PR China
| | - Ange Nzihou
- Université de Toulouse, IMT Mines Albi, RAPSODEE CNRS, UMR-5302, Jarlard, Albi 81013 Cedex 09, France
| | - Yiping Tai
- Institute of Hydrobiology, Jinan University, Guangzhou 510632, PR China
- Engineering Research Center of Tropical and Subtropical Aquatic Ecological Engineering, Ministry of Education, Guangzhou, PR China
| | - Ting Wei
- Department of Municipal and Environmental Engineering, Faculty of Water Resources and Hydroelectric Engineering, Xi'an University of Technology, Xi'an 710048, PR China
- Chemical Engineering Department, University of Alcalá, Madrid, Spain
| | - Cheng Shen
- Dooge Centre for Water Resources Research, School of Civil Engineering, University College Dublin, Belfield, Dublin 4, Ireland
- School of Environment and Natural Resources, Zhejiang University Sci. & Technol./Zhejiang Prov, Key Lab. of Recycling & Ecotreatment Waste, Hangzhou 310023, Zhejiang, PR China
| | - Yan Yang
- Dooge Centre for Water Resources Research, School of Civil Engineering, University College Dublin, Belfield, Dublin 4, Ireland
| | - Baimimng Ren
- Dooge Centre for Water Resources Research, School of Civil Engineering, University College Dublin, Belfield, Dublin 4, Ireland
- Université de Toulouse, IMT Mines Albi, RAPSODEE CNRS, UMR-5302, Jarlard, Albi 81013 Cedex 09, France
- School of Water and Environment, Chang'an University, Xi'an 710061, PR China
| | - Xingxing Wang
- Xi'an Hospital of Traditional Chinese Medicine, Xi 'an 710021, PR China
| | - Ya'e Wang
- School of Environmental and Municipal Engineering, Lanzhou Jiaotong University, Lanzhou 730070, PR China
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284
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Khan TR, Parker DS, Withers C. Mitigation of Airborne Contaminant Spread through Simple Interventions in an Occupied Single-Family Home. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:5880. [PMID: 34070834 PMCID: PMC8197807 DOI: 10.3390/ijerph18115880] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 05/27/2021] [Accepted: 05/27/2021] [Indexed: 12/23/2022]
Abstract
Historically, reducing aerosol-based transmission of respired viruses in indoor environments has been of importance for controlling influenza viruses and common-cold rhinoviruses. The present public health emergency associated with SARS-CoV-2 makes this topic critically important. Yet to be tested is the potential effectiveness of simple interventions that create an isolation zone (IZ) for a suspected/confirmed sick or sensitive person requiring quarantine. The intent in existing homes is to find a practical means to mitigate exposure to airborne contaminants. In creating an IZ in an occupied single-family home in the study, four simple strategies were tested. The test configurations were: (1) IZ windows closed with IZ bathroom exhaust ventilation fan off, (2) IZ windows closed with IZ exhaust fan on, (3) IZ window open with IZ exhaust fan off, and (4) IZ window open with IZ exhaust fan on. Incense-generated fine particulate matter (PM2.5) was used as a marker for virus transmission. The measured transfer of PM2.5 from the IZ into the main zone (MZ) of the house enabled us to determine the relative effectiveness of four containment strategies. Collectively, the data from pressure differential (across zones) and PM2.5 measurements suggested that the best containment strategy was achieved through continuously operating the bathroom exhaust fan while keeping the windows closed in the IZ (configuration 2). Interventions using open windows were found to be less reliable, due to variability in wind speed and direction, resulting in an unpredictable and sometimes detrimental pressure differential in the IZ with reference to MZ. Our findings strongly suggest a simple IZ exhaust ventilation strategy has the potential for mitigating the risk from the airborne spread of contaminants, such as SARS-CoV-2.
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Affiliation(s)
- Tanvir R. Khan
- FSEC Energy Research Center, University of Central Florida, Cocoa, FL 32922, USA; (D.S.P.); (C.W.)
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285
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Zhou L, Ayeh SK, Chidambaram V, Karakousis PC. Modes of transmission of SARS-CoV-2 and evidence for preventive behavioral interventions. BMC Infect Dis 2021; 21:496. [PMID: 34049515 PMCID: PMC8160404 DOI: 10.1186/s12879-021-06222-4] [Citation(s) in RCA: 76] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 05/21/2021] [Indexed: 01/12/2023] Open
Abstract
COVID-19 is a novel disease caused by SARS-CoV-2. During the global vaccination rollout, it is vital to thoroughly understand the modes of transmission of the virus in order to prevent further spread of variants and ultimately to end the pandemic. The current literature suggests that SARS-CoV-2 is transmitted among the human population primarily through respiratory droplets and, to a lesser extent, via aerosols. Transmission appears to be affected by temperature, humidity, precipitation, air currents, pH, and radiation in the ambient environment. Finally, the use of masks or facial coverings, social distancing, and hand washing are effective public health strategies in reducing the risk of exposure and transmission. Additional research is needed to further characterize the relative benefits of specific nonpharmaceutical interventions.
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Affiliation(s)
- Lucas Zhou
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Samuel K Ayeh
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Vignesh Chidambaram
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Petros C Karakousis
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Koch Cancer Research Building, 1550 Orleans St., Room 110, Baltimore, MD, 21287, USA.
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286
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Aerosols should not be defined by distance travelled. J Hosp Infect 2021; 115:131-132. [PMID: 34048848 PMCID: PMC8149158 DOI: 10.1016/j.jhin.2021.05.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Accepted: 05/16/2021] [Indexed: 01/21/2023]
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287
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Greenhalgh T, Ozbilgin M, Contandriopoulos D. Orthodoxy, illusio, and playing the scientific game: a Bourdieusian analysis of infection control science in the COVID-19 pandemic. Wellcome Open Res 2021; 6:126. [DOI: 10.12688/wellcomeopenres.16855.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/12/2021] [Indexed: 11/20/2022] Open
Abstract
Background: Scientific and policy bodies’ failure to acknowledge and act on the evidence base for airborne transmission of SARS-CoV-2 in a timely way is both a mystery and a scandal. In this study, we applied theories from Bourdieu to address the question, “How was a partial and partisan scientific account of SARS-CoV-2 transmission constructed and maintained, leading to widespread imposition of infection control policies which de-emphasised airborne transmission?”. Methods: From one international case study (the World Health Organisation) and four national ones (UK, Canada, USA and Japan), we selected a purposive sample of publicly available texts including scientific evidence summaries, guidelines, policy documents, public announcements, and social media postings. To analyse these, we applied Bourdieusian concepts of field, doxa, scientific capital, illusio, and game-playing. We explored in particular the links between scientific capital, vested interests, and policy influence. Results: Three fields—political, state (policy and regulatory), and scientific—were particularly relevant to our analysis. Political and policy actors at international, national, and regional level aligned—predominantly though not invariably—with medical scientific orthodoxy which promoted the droplet theory of transmission and considered aerosol transmission unproven or of doubtful relevance. This dominant scientific sub-field centred around the clinical discipline of infectious disease control, in which leading actors were hospital clinicians aligned with the evidence-based medicine movement. Aerosol scientists—typically, chemists, and engineers—representing the heterodoxy were systematically excluded from key decision-making networks and committees. Dominant discourses defined these scientists’ ideas and methodologies as weak, their empirical findings as untrustworthy or insignificant, and their contributions to debate as unhelpful. Conclusion: The hegemonic grip of medical infection control discourse remains strong. Exit from the pandemic depends on science and policy finding a way to renegotiate what Bourdieu called the ‘rules of the scientific game’—what counts as evidence, quality, and rigour.
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288
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Hofer S, Hofstätter N, Duschl A, Himly M. SARS-CoV-2-Laden Respiratory Aerosol Deposition in the Lung Alveolar-Interstitial Region Is a Potential Risk Factor for Severe Disease: A Modeling Study. J Pers Med 2021; 11:431. [PMID: 34069409 PMCID: PMC8159114 DOI: 10.3390/jpm11050431] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 05/10/2021] [Accepted: 05/17/2021] [Indexed: 12/23/2022] Open
Abstract
COVID-19, predominantly a mild disease, is associated with more severe clinical manifestation upon pulmonary involvement. Virion-laden aerosols and droplets target different anatomical sites for deposition. Compared to droplets, aerosols more readily advance into the peripheral lung. We performed in silico modeling to confirm the secondary pulmonary lobules as the primary site of disease initiation. By taking different anatomical aerosol origins into consideration and reflecting aerosols from exhalation maneuvers breathing and vocalization, the physicochemical properties of generated respiratory aerosol particles were defined upon conversion to droplet nuclei by evaporation at ambient air. To provide detailed, spatially-resolved information on particle deposition in the thoracic region of the lung, a top-down refinement approach was employed. Our study presents evidence for hot spots of aerosol deposition in lung generations beyond the terminal bronchiole, with a maximum in the secondary pulmonary lobules and a high preference to the lower lobes of both lungs. In vivo, initial chest CT anomalies, the ground glass opacities, resulting from partial alveolar filling and interstitial thickening in the secondary pulmonary lobules, are likewise localized in these lung generations, with the highest frequency in both lower lobes and in the early stage of disease. Hence, our results suggest a disease initiation right there upon inhalation of virion-laden respiratory aerosols, linking the aerosol transmission route to pathogenesis associated with higher disease burden and identifying aerosol transmission as a new independent risk factor for developing a pulmonary phase with a severe outcome.
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Affiliation(s)
| | | | | | - Martin Himly
- Department of Biosciences, Paris Lodron University of Salzburg (PLUS), 5020 Salzburg, Austria; (S.H.); (N.H.); (A.D.)
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289
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Sobolik JS, Sajewski ET, Jaykus LA, Cooper DK, Lopman BA, Kraay ANM, Ryan PB, Leon JS. Controlling risk of SARS-CoV-2 infection in essential workers of enclosed food manufacturing facilities. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2021:2021.05.14.21257244. [PMID: 34031667 PMCID: PMC8142669 DOI: 10.1101/2021.05.14.21257244] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The SARS-CoV-2 global pandemic poses significant health risks to workers who are essential to maintaining the food supply chain. Using a quantitative risk assessment model, this study characterized the impact of risk reduction strategies for controlling SARS-CoV-2 transmission (droplet, aerosol, fomite-mediated) among front-line workers in a representative enclosed food manufacturing facility. We simulated: 1) individual and cumulative SARS-CoV-2 infection risks from close contact (droplet and aerosols at 1-3m), aerosol, and fomite-mediated exposures to a susceptible worker following exposure to an infected worker during an 8h-shift; and 2) the relative reduction in SARS-CoV-2 infection risk attributed to infection control interventions (physical distancing, mask use, ventilation, surface disinfection, hand hygiene). Without mitigation measures, the SARS-CoV-2 infection risk was largest for close contact (droplet and aerosol) at 1m (0.96, 95%CI: 0.67-1.0). In comparison, risk associated with fomite (0.26, 95%CI: 0.10-0.56) or aerosol exposure alone (0.05, 95%CI: 0.01-0.13) at 1m distance was substantially lower (73-95%). At 1m, droplet transmission predominated over aerosol and fomite-mediated transmission, however, this changed by 3m, with aerosols comprising the majority of the exposure dose. Increasing physical distancing reduced risk by 84% (1 to 2m) and 91% (1 to 3m). Universal mask use reduced infection risk by 52-88%, depending on mask type. Increasing ventilation (from 0.1 to 2-8 air changes/hour) resulted in risk reductions of 14-54% (1m) and 55-85% (2m). Combining these strategies, together with handwashing and surface disinfection, resulted in <1% infection risk. Current industry SARS-CoV-2 risk reduction strategies, particularly when bundled, provide significant protection to essential food workers. SIGNIFICANCE STATEMENT Using mathematical modeling, we find that workers in enclosed food manufacturing facilities are at higher risk of SARS-CoV-2 infection from close contact transmission (exposure to large droplets and small aerosol particles) than fomite transmission. Thus, strategies protecting workers should prioritize close contact transmission pathways, such as physical distancing, universal mask use, and room air changes, with surface disinfection (reducing fomite transmission) and handwashing of secondary importance. Our work supports current international (EU-OSHA), domestic (FDA, OSHA), and food industry-standard guidance for managing COVID-19 transmission in essential workers in the food manufacturing sector. Although our model was designed for an indoor food manufacturing setting, it can be readily adapted to other indoor environments and infectious respiratory pathogens.
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Affiliation(s)
- Julia S. Sobolik
- Rollins School of Public Health, Emory University, Atlanta, GA USA
| | | | - Lee-Ann Jaykus
- Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Raleigh, NC, 27695
| | - D. Kane Cooper
- Rollins School of Public Health, Emory University, Atlanta, GA USA
| | - Ben A. Lopman
- Rollins School of Public Health, Emory University, Atlanta, GA USA
| | - Alicia NM. Kraay
- Rollins School of Public Health, Emory University, Atlanta, GA USA
| | - P. Barry Ryan
- Rollins School of Public Health, Emory University, Atlanta, GA USA
| | - Juan S. Leon
- Rollins School of Public Health, Emory University, Atlanta, GA USA
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290
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Peng Z, Jimenez JL. Exhaled CO 2 as a COVID-19 Infection Risk Proxy for Different Indoor Environments and Activities. ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS 2021; 8:392-397. [PMID: 37566374 PMCID: PMC8043197 DOI: 10.1021/acs.estlett.1c00183] [Citation(s) in RCA: 97] [Impact Index Per Article: 32.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 04/01/2021] [Accepted: 04/02/2021] [Indexed: 05/21/2023]
Abstract
CO2 is co-exhaled with aerosols containing SARS-CoV-2 by COVID-19-infected people and can be used as a proxy of SARS-CoV-2 concentrations indoors. Indoor CO2 measurements by low-cost sensors hold promise for mass monitoring of indoor aerosol transmission risk for COVID-19 and other respiratory diseases. We derive analytical expressions of CO2-based risk proxies and apply them to various typical indoor environments. The relative infection risk in a given environment scales with excess CO2 level, and thus, keeping CO2 as low as feasible in a space allows optimization of the protection provided by ventilation. We show that the CO2 level corresponding to a given absolute infection risk varies by >2 orders of magnitude for different environments and activities. Although large uncertainties, mainly from virus exhalation rates, are still associated with infection risk estimates, our study provides more specific and practical recommendations for low-cost CO2-based indoor infection risk monitoring.
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Affiliation(s)
- Zhe Peng
- Cooperative Institute for Research in Environmental Sciences and Department
of Chemistry, University of Colorado, Boulder, Colorado 80309,
United States
| | - Jose L. Jimenez
- Cooperative Institute for Research in Environmental Sciences and Department
of Chemistry, University of Colorado, Boulder, Colorado 80309,
United States
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291
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Robie ER, Abdelgadir A, Binder RA, Gray GC. Live SARS-CoV-2 is difficult to detect in patient aerosols. Influenza Other Respir Viruses 2021; 15:554-557. [PMID: 33939268 PMCID: PMC8189214 DOI: 10.1111/irv.12860] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/28/2021] [Indexed: 01/12/2023] Open
Affiliation(s)
- Emily R Robie
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, NC, USA.,Duke Global Health Institute, Duke University, Durham, NC, USA
| | - Anfal Abdelgadir
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, NC, USA.,Duke Global Health Institute, Duke University, Durham, NC, USA
| | - Raquel A Binder
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, NC, USA.,Duke Global Health Institute, Duke University, Durham, NC, USA
| | - Gregory C Gray
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, NC, USA.,Duke Global Health Institute, Duke University, Durham, NC, USA.,Global Health Research Center, Duke Kunshan University, Kunshan, China.,Program in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, Singapore
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292
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Nardell EA. Air Disinfection for Airborne Infection Control with a Focus on COVID-19: Why Germicidal UV is Essential †. Photochem Photobiol 2021; 97:493-497. [PMID: 33759191 PMCID: PMC8251047 DOI: 10.1111/php.13421] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 03/16/2021] [Indexed: 01/03/2023]
Abstract
Aerosol transmission is now widely accepted as the principal way that COVID-19 is spread, as has the importance of ventilation-natural and mechanical. But in other than healthcare facilities, mechanical ventilation is designed for comfort, not airborne infection control, and cannot achieve the 6 to 12 room air changes per hour recommended for airborne infection control. More efficient air filters have been recommended in ventilation ducts despite a lack of convincing evidence that SARS-CoV-2 virus spreads through ventilation systems. Most transmission appears to occur in rooms where both an infectious source COVID-19 case and other susceptible occupants share the same air. Only two established room-based technologies are available to supplement mechanical ventilation: portable room air cleaners and upper room germicidal UV air disinfection. Portable room air cleaners can be effective, but performance is limited by their clean air delivery rate relative to room volume. SARS-CoV-2 is highly susceptible to GUV, an 80-year-old technology that has been shown to safely, quietly, effectively and economically produce the equivalent of 10 to 20 or more air changes per hour under real life conditions. For these reasons, upper room GUV is the essential engineering intervention for reducing COVID-19 spread.
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Affiliation(s)
- Edward A. Nardell
- Division of Global Health EquityBrigham & Women’s HospitalHarvard Medical SchoolBostonMAUSA
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293
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Haas CN. Action Levels for SARS-CoV-2 in Air: Preliminary Approach. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2021; 41:705-709. [PMID: 33818802 PMCID: PMC8251121 DOI: 10.1111/risa.13728] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Quantitative microbial risk assessment has been used to develop criteria for exposure to many microorganisms. In this article, the dose-response curve for Coronavirus 229E is used to develop preliminary risk-based exposure criteria for SARS-CoV-2 via the respiratory portals of entry.
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Affiliation(s)
- Charles N. Haas
- Department of Civil, Architectural and Environmental EngineeringDrexel UniversityPhiladelphiaPAUSA
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294
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He R, Liu W, Elson J, Vogt R, Maranville C, Hong J. Airborne transmission of COVID-19 and mitigation using box fan air cleaners in a poorly ventilated classroom. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:057107. [PMID: 34040337 PMCID: PMC8142835 DOI: 10.1063/5.0050058] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 04/02/2021] [Indexed: 05/04/2023]
Abstract
Many indoor places, including aged classrooms and offices, prisons, homeless shelters, etc., are poorly ventilated but resource-limited to afford expensive ventilation upgrades or commercial air purification systems, raising concerns on the safety of opening activities in these places in the era of the COVID-19 pandemic. To address this challenge, using computational fluid dynamics, we conducted a systematic investigation of airborne transmission in a classroom equipped with a single horizontal unit ventilator (HUV) and evaluate the performance of a low-cost box fan air cleaner for risk mitigation. Our study shows that placing box fan air cleaners in the classroom results in a substantial reduction of airborne transmission risk across the entire space. The air cleaner can achieve optimal performance when placed near the asymptomatic patient. However, without knowing the location of the patient, the performance of the cleaner is optimal near the HUV with the air flowing downwards. In addition, we find that it is more efficient in reducing aerosol concentration and spread in the classroom by adding air cleaners in comparison with raising the flow rate of HUV alone. The number and placement of air cleaners need to be adjusted to maintain their efficacy for larger classrooms and to account for the thermal gradient associated with a human thermal plume and hot ventilation air during cold seasons. Overall, our study shows that box fan air cleaners can serve as an effective low-cost alternative for mitigating airborne transmission risks in poorly ventilated spaces.
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Affiliation(s)
| | - Wanjiao Liu
- Research and Advanced Engineering, Ford Motor Company, 2101 Village Road, Dearborn, Michigan 48121, USA
| | - John Elson
- Research and Advanced Engineering, Ford Motor Company, 2101 Village Road, Dearborn, Michigan 48121, USA
| | - Rainer Vogt
- Ford-Werke GmbH, Research & Innovation Center, 52072 Aachen, Germany
| | - Clay Maranville
- Research and Advanced Engineering, Ford Motor Company, 2101 Village Road, Dearborn, Michigan 48121, USA
| | - Jiarong Hong
- Author to whom correspondence should be addressed:
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295
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Farthing TS, Lanzas C. When can we stop wearing masks? Agent-based modeling to identify when vaccine coverage makes nonpharmaceutical interventions for reducing SARS-CoV-2 infections redundant in indoor gatherings. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2021:2021.04.19.21255737. [PMID: 33948613 PMCID: PMC8095232 DOI: 10.1101/2021.04.19.21255737] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
As vaccination efforts to combat the COVID-19 pandemic are ramping up worldwide, there are rising concerns that individuals will begin to eschew nonpharmaceutical interventions for preventing SARS-CoV-2 transmission and attempt to return to pre-pandemic normalcy before vaccine coverage levels effectively mitigate transmission risk. In the U.S.A., some governing bodies have already weakened or repealed guidelines for nonpharmaceutical intervention use, despite a recent spike in national COVID-19 cases and majority population of unvaccinated individuals. Recent modeling suggests that repealing nonpharmaceutical intervention guidelines too early into vaccine rollouts will lead to localized increases in COVID-19 cases, but the magnitude of nonpharmaceutical intervention effects on individual-level SARS-CoV-2 infection risk in fully- and partially-vaccinated populations is unclear. We use a previously-published agent-based model to simulate SARS-CoV-2 transmission in indoor gatherings of varying durations, population densities, and vaccination coverage levels. By simulating nonpharmaceutical interventions in some gatherings but not others, we were able to quantify the difference in SARS-CoV-2 infection risk when nonpharmaceutical interventions were used, relative to scenarios with no nonpharmaceutical interventions. We found that nonpharmaceutical interventions will often reduce secondary attack rates, especially during brief interactions, and therefore there is no definitive vaccination coverage level that makes nonpharmaceutical interventions completely redundant. However, the reduction effect on absolute SARS-CoV-2 infection risk conferred by nonpharmaceutical interventions is likely proportional to COVID-19 prevalence. Therefore, if COVID-19 prevalence decreases in the future, nonpharmaceutical interventions will likely still confer protective effects but potential benefits may be small enough to remain within "effectively negligible" risk thresholds.
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Affiliation(s)
| | - Cristina Lanzas
- North Carolina State University, Raleigh, North Carolina, USA
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296
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Bazant MZ, Bush JWM. A guideline to limit indoor airborne transmission of COVID-19. Proc Natl Acad Sci U S A 2021; 118:e2018995118. [PMID: 33858987 PMCID: PMC8092463 DOI: 10.1073/pnas.2018995118] [Citation(s) in RCA: 188] [Impact Index Per Article: 62.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 03/03/2021] [Indexed: 12/15/2022] Open
Abstract
The current revival of the American economy is being predicated on social distancing, specifically the Six-Foot Rule, a guideline that offers little protection from pathogen-bearing aerosol droplets sufficiently small to be continuously mixed through an indoor space. The importance of airborne transmission of COVID-19 is now widely recognized. While tools for risk assessment have recently been developed, no safety guideline has been proposed to protect against it. We here build on models of airborne disease transmission in order to derive an indoor safety guideline that would impose an upper bound on the "cumulative exposure time," the product of the number of occupants and their time in an enclosed space. We demonstrate how this bound depends on the rates of ventilation and air filtration, dimensions of the room, breathing rate, respiratory activity and face mask use of its occupants, and infectiousness of the respiratory aerosols. By synthesizing available data from the best-characterized indoor spreading events with respiratory drop size distributions, we estimate an infectious dose on the order of 10 aerosol-borne virions. The new virus (severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]) is thus inferred to be an order of magnitude more infectious than its forerunner (SARS-CoV), consistent with the pandemic status achieved by COVID-19. Case studies are presented for classrooms and nursing homes, and a spreadsheet and online app are provided to facilitate use of our guideline. Implications for contact tracing and quarantining are considered, and appropriate caveats enumerated. Particular consideration is given to respiratory jets, which may substantially elevate risk when face masks are not worn.
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Affiliation(s)
- Martin Z Bazant
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139;
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - John W M Bush
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139
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297
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Bazant MZ, Bush JWM. A guideline to limit indoor airborne transmission of COVID-19. Proc Natl Acad Sci U S A 2021; 118:2018995118. [PMID: 33858987 DOI: 10.1101/2020.08.26.20182824v3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/24/2023] Open
Abstract
The current revival of the American economy is being predicated on social distancing, specifically the Six-Foot Rule, a guideline that offers little protection from pathogen-bearing aerosol droplets sufficiently small to be continuously mixed through an indoor space. The importance of airborne transmission of COVID-19 is now widely recognized. While tools for risk assessment have recently been developed, no safety guideline has been proposed to protect against it. We here build on models of airborne disease transmission in order to derive an indoor safety guideline that would impose an upper bound on the "cumulative exposure time," the product of the number of occupants and their time in an enclosed space. We demonstrate how this bound depends on the rates of ventilation and air filtration, dimensions of the room, breathing rate, respiratory activity and face mask use of its occupants, and infectiousness of the respiratory aerosols. By synthesizing available data from the best-characterized indoor spreading events with respiratory drop size distributions, we estimate an infectious dose on the order of 10 aerosol-borne virions. The new virus (severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]) is thus inferred to be an order of magnitude more infectious than its forerunner (SARS-CoV), consistent with the pandemic status achieved by COVID-19. Case studies are presented for classrooms and nursing homes, and a spreadsheet and online app are provided to facilitate use of our guideline. Implications for contact tracing and quarantining are considered, and appropriate caveats enumerated. Particular consideration is given to respiratory jets, which may substantially elevate risk when face masks are not worn.
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Affiliation(s)
- Martin Z Bazant
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139;
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - John W M Bush
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139
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298
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Kifle ZD, Ayele AG, Enyew EF. Drug Repurposing Approach, Potential Drugs, and Novel Drug Targets for COVID-19 Treatment. JOURNAL OF ENVIRONMENTAL AND PUBLIC HEALTH 2021; 2021:6631721. [PMID: 33953756 PMCID: PMC8063850 DOI: 10.1155/2021/6631721] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 02/23/2021] [Accepted: 04/17/2021] [Indexed: 12/16/2022]
Abstract
Novel coronavirus first appeared in Wuhan, China, in December 2019, and it speedily expanded globally. Some medications which are used to treat other diseases seem to be effective in treating COVID-19 even without explicit support. The existing drugs that are summarized in this review primarily focused on therapeutic agents that possessed activity against other RNA viruses such as MERS-CoV and SARS-CoV. Drug repurposing or repositioning is a promising field in drug discovery that identifies new therapeutic opportunities for existing drugs such as corticosteroids, RNA-dependent RNA polymerase inhibitors, interferons, protease inhibitors, ivermectin, melatonin, teicoplanin, and some others. A search for new drug/drug targets is underway. Thus, blocking coronavirus structural protein, targeting viral enzyme, dipeptidyl peptidase 4, and membrane fusion blocker (angiotensin-converting enzyme 2 and CD147 inhibitor) are major sites based on molecular targets for the management of COVID-19 infection. The possible impact of biologics for the management of COVID19 is promising and includes a wide variety of options such as cytokines, nucleic acid-based therapies targeting virus gene expression, bioengineered and vectored antibodies, and various types of vaccines. This review demonstrates that the available data are not sufficient to suggest any treatment for the eradication of COVID-19 to be used at the clinical level. This article aims to review the roles of existing drugs and drug targets for COVID-19 treatment.
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Affiliation(s)
- Zemene Demelash Kifle
- Department of Pharmacology, School of Pharmacy, College of Medicine and Health Science, University of Gondar, Gondar, Ethiopia
| | - Akeberegn Gorems Ayele
- Department of Pharmacology and Clinical Pharmacy, School of Pharmacy, College of Health Science, Addis Ababa University, Addis Ababa, Ethiopia
| | - Engidaw Fentahun Enyew
- Department of Human Anatomy, School of Medicine, College of Medicine and Health Sciences, Gondar, Ethiopia
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Goldberg EM, Bingaman CS, Perera S, Ranney ML. MyCOVIDRisk app: development and utilisation of a COVID-19 risk assessment and mitigation application. BMJ INNOVATIONS 2021; 7:363-367. [PMID: 37556244 PMCID: PMC8011423 DOI: 10.1136/bmjinnov-2021-000672] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 03/01/2021] [Accepted: 03/06/2021] [Indexed: 01/06/2023]
Affiliation(s)
- Elizabeth M Goldberg
- Department of Emergency
Medicine, Warren Alpert Medical School of Brown
University, Providence,
Rhode Island, USA
- Brown-Lifespan Center
for Digital Health, Brown University, Providence, Rhode
Island, USA
| | - Charlotte S Bingaman
- Brown-Lifespan Center
for Digital Health, Brown University, Providence, Rhode
Island, USA
| | - Sudheesha Perera
- Department of Emergency
Medicine, Warren Alpert Medical School of Brown
University, Providence,
Rhode Island, USA
| | - Megan L Ranney
- Department of Emergency
Medicine, Warren Alpert Medical School of Brown
University, Providence,
Rhode Island, USA
- Brown-Lifespan Center
for Digital Health, Brown University, Providence, Rhode
Island, USA
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300
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Nordsiek F, Bodenschatz E, Bagheri G. Risk assessment for airborne disease transmission by poly-pathogen aerosols. PLoS One 2021; 16:e0248004. [PMID: 33831003 PMCID: PMC8031403 DOI: 10.1371/journal.pone.0248004] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 02/17/2021] [Indexed: 02/03/2023] Open
Abstract
In the case of airborne diseases, pathogen copies are transmitted by droplets of respiratory tract fluid that are exhaled by the infectious that stay suspended in the air for some time and, after partial or full drying, inhaled as aerosols by the susceptible. The risk of infection in indoor environments is typically modelled using the Wells-Riley model or a Wells-Riley-like formulation, usually assuming the pathogen dose follows a Poisson distribution (mono-pathogen assumption). Aerosols that hold more than one pathogen copy, i.e. poly-pathogen aerosols, break this assumption even if the aerosol dose itself follows a Poisson distribution. For the largest aerosols where the number of pathogen in each aerosol can sometimes be several hundred or several thousand, the effect is non-negligible, especially in diseases where the risk of infection per pathogen is high. Here we report on a generalization of the Wells-Riley model and dose-response models for poly-pathogen aerosols by separately modeling each number of pathogen copies per aerosol, while the aerosol dose itself follows a Poisson distribution. This results in a model for computational risk assessment suitable for mono-/poly-pathogen aerosols. We show that the mono-pathogen assumption significantly overestimates the risk of infection for high pathogen concentrations in the respiratory tract fluid. The model also includes the aerosol removal due to filtering by the individuals which becomes significant for poorly ventilated environments with a high density of individuals, and systematically includes the effects of facemasks in the infectious aerosol source and sink terms and dose calculations.
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Affiliation(s)
- Freja Nordsiek
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Göttingen, Niedersachsen, Germany
| | - Eberhard Bodenschatz
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Göttingen, Niedersachsen, Germany
- Institute for Dynamics of Complex Systems, University of Göttingen, Göttingen, Niedersachsen, Germany
- Laboratory of Atomic and Solid State Physics and Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York, United States of America
| | - Gholamhossein Bagheri
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Göttingen, Niedersachsen, Germany
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