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Edwards AJ, King MF, Noakes CJ, Peckham D, López-García M. The Wells-Riley model revisited: Randomness, heterogeneity, and transient behaviours. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2024; 44:2125-2147. [PMID: 38501447 DOI: 10.1111/risa.14295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Revised: 02/26/2024] [Accepted: 02/29/2024] [Indexed: 03/20/2024]
Abstract
The Wells-Riley model has been widely used to estimate airborne infection risk, typically from a deterministic point of view (i.e., focusing on the average number of infections) or in terms of a per capita probability of infection. Some of its main limitations relate to considering well-mixed air, steady-state concentration of pathogen in the air, a particular amount of time for the indoor interaction, and that all individuals are homogeneous and behave equally. Here, we revisit the Wells-Riley model, providing a mathematical formalism for its stochastic version, where the number of infected individuals follows a Binomial distribution. Then, we extend the Wells-Riley methodology to consider transient behaviours, randomness, and population heterogeneity. In particular, we provide analytical solutions for the number of infections and the per capita probability of infection when: (i) susceptible individuals remain in the room after the infector leaves, (ii) the duration of the indoor interaction is random/unknown, and (iii) infectors have heterogeneous quanta production rates (or the quanta production rate of the infector is random/unknown). We illustrate the applicability of our new formulations through two case studies: infection risk due to an infectious healthcare worker (HCW) visiting a patient, and exposure during lunch for uncertain meal times in different dining settings. Our results highlight that infection risk to a susceptible who remains in the space after the infector leaves can be nonnegligible, and highlight the importance of incorporating uncertainty in the duration of the indoor interaction and the infectivity of the infector when estimating risk.
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Affiliation(s)
- Alexander J Edwards
- EPSRC Centre for Doctoral Training in Fluid Dynamics, University of Leeds, Leeds, UK
| | | | | | - Daniel Peckham
- Leeds Institute of Medical Research, University of Leeds, Leeds, UK
- Leeds Teaching Hospitals NHS Trust, Leeds, UK
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Morawska L, Li Y, Salthammer T. Lessons from the COVID-19 pandemic for ventilation and indoor air quality. Science 2024; 385:396-401. [PMID: 39052782 DOI: 10.1126/science.adp2241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Accepted: 06/07/2024] [Indexed: 07/27/2024]
Abstract
The rapid global spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at the beginning of 2020 presented the world with its greatest health challenge in decades. It soon became clear that governments were unprepared to respond appropriately to this crisis. National and international public health authorities were confused about the transmission routes of the virus and the control measures required to protect against it. In particular, the need to reduce the risk of infection through sufficient and effective ventilation of indoor spaces was given little attention. In this review, we discuss insights and key lessons learned from the COVID-19 pandemic regarding the role of ventilation as an effective means against airborne transmission of pathogens and, more broadly, for supporting good indoor air quality.
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Affiliation(s)
- Lidia Morawska
- Queensland University of Technology, International Laboratory for Air Quality and Health, Brisbane, QLD 4000, Australia
- Global Centre for Clean Air Research (GCARE), School of Sustainability, Civil and Environmental Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH, UK
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
| | - Tunga Salthammer
- Queensland University of Technology, International Laboratory for Air Quality and Health, Brisbane, QLD 4000, Australia
- Department of Material Analysis and Indoor Chemistry, Fraunhofer WKI, Braunschweig 38108, Germany
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3
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Rosenblatt E, Cook JD, DiRenzo GV, Grant EHC, Arce F, Pepin KM, Rudolph FJ, Runge MC, Shriner S, Walsh DP, Mosher BA. Epidemiological modeling of SARS-CoV-2 in white-tailed deer (Odocoileus virginianus) reveals conditions for introduction and widespread transmission. PLoS Comput Biol 2024; 20:e1012263. [PMID: 38995977 PMCID: PMC11268674 DOI: 10.1371/journal.pcbi.1012263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 07/24/2024] [Accepted: 06/18/2024] [Indexed: 07/14/2024] Open
Abstract
Emerging infectious diseases with zoonotic potential often have complex socioecological dynamics and limited ecological data, requiring integration of epidemiological modeling with surveillance. Although our understanding of SARS-CoV-2 has advanced considerably since its detection in late 2019, the factors influencing its introduction and transmission in wildlife hosts, particularly white-tailed deer (Odocoileus virginianus), remain poorly understood. We use a Susceptible-Infected-Recovered-Susceptible epidemiological model to investigate the spillover risk and transmission dynamics of SARS-CoV-2 in wild and captive white-tailed deer populations across various simulated scenarios. We found that captive scenarios pose a higher risk of SARS-CoV-2 introduction from humans into deer herds and subsequent transmission among deer, compared to wild herds. However, even in wild herds, the transmission risk is often substantial enough to sustain infections. Furthermore, we demonstrate that the strength of introduction from humans influences outbreak characteristics only to a certain extent. Transmission among deer was frequently sufficient for widespread outbreaks in deer populations, regardless of the initial level of introduction. We also explore the potential for fence line interactions between captive and wild deer to elevate outbreak metrics in wild herds that have the lowest risk of introduction and sustained transmission. Our results indicate that SARS-CoV-2 could be introduced and maintained in deer herds across a range of circumstances based on testing a range of introduction and transmission risks in various captive and wild scenarios. Our approach and findings will aid One Health strategies that mitigate persistent SARS-CoV-2 outbreaks in white-tailed deer populations and potential spillback to humans.
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Affiliation(s)
- Elias Rosenblatt
- Rubenstein School of Environment and Natural Resources, University of Vermont, Burlington, Vermont, United States of America
| | - Jonathan D. Cook
- U.S. Geological Survey, Eastern Ecological Science Center, Laurel, Maryland, United States of America
| | - Graziella V. DiRenzo
- U. S. Geological Survey, Massachusetts Cooperative Fish and Wildlife Research Unit, University of Massachusetts, Amherst, Massachusetts, United States of America
- Department of Environmental Conservation, University of Massachusetts, Amherst, Massachusetts, United States of America
| | - Evan H. Campbell Grant
- U.S. Geological Survey, Eastern Ecological Science Center, Turner’s Falls, Massachusetts, United States of America
| | - Fernando Arce
- Department of Environmental Conservation, University of Massachusetts, Amherst, Massachusetts, United States of America
| | - Kim M. Pepin
- National Wildlife Research Center, USDA, APHIS, Fort Collins, Colorado, United States of America
| | - F. Javiera Rudolph
- U.S. Geological Survey, Eastern Ecological Science Center, Laurel, Maryland, United States of America
- Department of Ecosystem Sciences and Management, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Michael C. Runge
- U.S. Geological Survey, Eastern Ecological Science Center, Laurel, Maryland, United States of America
| | - Susan Shriner
- National Wildlife Research Center, USDA, APHIS, Fort Collins, Colorado, United States of America
| | - Daniel P. Walsh
- U. S. Geological Survey, Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, Montana, United States of America
| | - Brittany A. Mosher
- Rubenstein School of Environment and Natural Resources, University of Vermont, Burlington, Vermont, United States of America
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Aganovic A, Kurnitski J, Wargocki P. A quanta-independent approach for the assessment of strategies to reduce the risk of airborne infection. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 927:172278. [PMID: 38583631 DOI: 10.1016/j.scitotenv.2024.172278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 04/02/2024] [Accepted: 04/04/2024] [Indexed: 04/09/2024]
Abstract
The Wells-Riley model is extensively used for retrospective and prospective modelling of the risk of airborne transmission of infection in indoor spaces. It is also used when examining the efficacy of various removal and deactivation methods for airborne infectious aerosols in the indoor environment, which is crucial when selecting the most effective infection control technologies. The problem is that the large variation in viral load between individuals makes the Wells-Riley model output very sensitive to the input parameters and may yield a flawed prediction of risk. The absolute infection risk estimated with this model can range from nearly 0 % to 100 % depending on the viral load, even when all other factors, such as removal mechanisms and room geometry, remain unchanged. We therefore propose a novel method that removes this sensitivity to viral load. We define a quanta-independent maximum absolute before-after difference in infection risk that is independent of quanta factors like viral load, physical activity, or the dose-response relationships. The input data needed for a non-steady-state calculation are just the removal rates, room volume, and occupancy duration. Under steady-state conditions the approach provides an elegant solution that is only dependent on removal mechanisms before and after applying infection control measures. We applied this method to compare the impact of relative humidity, ventilation rate and its effectiveness, filtering efficiency, and the use of ultraviolet germicidal irradiation on the infection risk. The results demonstrate that the method provides a comprehensive understanding of the impact of infection control strategies on the risk of airborne infection, enabling rational decisions to be made regarding the most effective strategies in a specific context. The proposed method thus provides a practical tool for mitigation of airborne infection risk.
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Affiliation(s)
- Amar Aganovic
- Department of Automation and Process Engineering, UiT The Arctic University of Norway, Tromsø, Norway.
| | - Jarek Kurnitski
- Department of Civil Engineering and Architecture, Tallinn University of Technology, Tallinn, Estonia; Department of Civil Engineering, Aalto university, Espoo, Finland
| | - Pawel Wargocki
- Department of Environmental and Resource Engineering, Technical University of Denmark, Copenhagen, Denmark
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5
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Edwards AJ, King MF, López-García M, Peckham D, Noakes CJ. Assessing the effects of transient weather conditions on airborne transmission risk in naturally ventilated hospitals. J Hosp Infect 2024; 148:1-10. [PMID: 38447806 DOI: 10.1016/j.jhin.2024.02.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Revised: 02/21/2024] [Accepted: 02/22/2024] [Indexed: 03/08/2024]
Abstract
BACKGROUND Many UK hospitals rely heavily on natural ventilation as their main source of airflow in patient wards. This method of ventilation can have cost and energy benefits, but it may lead to unpredictable flow patterns between indoor spaces, potentially leading to the unexpected transport of infectious material to other connecting zones. However, the effects of weather conditions on airborne transmission are often overlooked. METHODS A multi-zone CONTAM model of a naturally ventilated hospital respiratory ward, incorporating time-varying weather, was proposed. Coupling this with an airborne infection model, this study assessed the variable risk in interconnected spaces, focusing particularly on occupancy, disease and ventilation scenarios based on a UK respiratory ward. RESULTS The results suggest that natural ventilation with varying weather conditions can cause irregularities in the ventilation rates and interzonal flow rates of connected zones, leading to infrequent but high peaks in the concentration of airborne pathogens in particular rooms. This transient behaviour increases the risk of airborne infection, particularly through movement of pathogens between rooms, and highlights that large outbreaks may be more likely under certain conditions. This study demonstrated how ventilation rates achieved by natural ventilation are likely to fall below the recommended guidance, and that the implementation of supplemental mechanical ventilation can increase ventilation rates and reduce the variability in infection risks. CONCLUSION This model emphasises the need for consideration of transient external conditions when assessing the risk of transmission of airborne infection in indoor environments.
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Affiliation(s)
- A J Edwards
- EPSRC Centre for Doctoral Training in Fluid Dynamics, University of Leeds, Leeds, UK.
| | - M-F King
- School of Civil Engineering, University of Leeds, Leeds, UK
| | | | - D Peckham
- Leeds Institute of Medical Research, University of Leeds, Leeds, UK; Leeds Teaching Hospitals NHS Trust, Leeds, UK
| | - C J Noakes
- School of Civil Engineering, University of Leeds, Leeds, UK
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Feng Y, Luo X, Wei J, Fan Y, Ge J. Evaluating infection risks in buses based on passengers' dynamic temporal and typical spatial scenarios: A case study of COVID-19. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 922:171373. [PMID: 38428616 DOI: 10.1016/j.scitotenv.2024.171373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 02/23/2024] [Accepted: 02/27/2024] [Indexed: 03/03/2024]
Abstract
Conventional buses, as an indispensable part of the urban public transport system, impose cross-infection risks on passengers. To assess differential risks due to dynamic staying durations and locations, this study considered four spatial distributions (i = 1-4) and six temporal scenarios (j = 1-6) of buses. Based on field measurements and a risk assessment approach combining both short-range and room-scale effects, risks are evaluated properly. The results showed that temporal asynchrony between infected and susceptible individuals significantly affects disease transmission rates. The Control Case assumes that infected and susceptible individuals enter and leave synchronously. However, ignoring temporal asynchrony scenarios, i.e., the Control Case, resulted in overestimation (+30.7 % to +99.6 %) or underestimation (-15.2 % to -69.9 %) of the actual risk. Moreover, the relative difference ratios of room-scale risks between the Control Case and five temporal scenarios are impacted by ventilation. Short-range risk exists only if infected and susceptible individuals have temporal overlap on the bus. Considering temporal and spatial asynchrony, a more realistic total reproduction number (R) can be obtained. Subsequently, the total R was assessed under five temporal scenarios. On average, for the Control Case, the total R was estimated to be +27.3 % higher than j = 1, -9.3 % lower than j = 2, +12.8 % higher than j = 3, +33.0 % lower than j = 4, and + 77.6 % higher than j = 5. This implies the need for a combination of active prevention and real-time risk monitoring to enable rigid travel demand and control the spread of the epidemic.
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Affiliation(s)
- Yinshuai Feng
- College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, China; International Research Center for Green Building and Low-Carbon City, International Campus, Zhejiang University, Haining, China
| | - Xiaoyu Luo
- College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, China; International Research Center for Green Building and Low-Carbon City, International Campus, Zhejiang University, Haining, China
| | - Jianjian Wei
- Institute of Refrigeration and Cryogenics, Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Zhejiang University, Hangzhou, China
| | - Yifan Fan
- College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, China; International Research Center for Green Building and Low-Carbon City, International Campus, Zhejiang University, Haining, China.
| | - Jian Ge
- College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, China; International Research Center for Green Building and Low-Carbon City, International Campus, Zhejiang University, Haining, China
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Banholzer N, Schmutz R, Middelkoop K, Hella J, Egger M, Wood R, Fenner L. Airborne transmission risks of tuberculosis and COVID-19 in schools in South Africa, Switzerland, and Tanzania: Modeling of environmental data. PLOS GLOBAL PUBLIC HEALTH 2024; 4:e0002800. [PMID: 38236801 PMCID: PMC10796007 DOI: 10.1371/journal.pgph.0002800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 12/18/2023] [Indexed: 01/22/2024]
Abstract
The COVID-19 pandemic renewed interest in airborne transmission of respiratory infections, particularly in congregate indoor settings, such as schools. We modeled transmission risks of tuberculosis (caused by Mycobacterium tuberculosis, Mtb) and COVID-19 (caused by SARS-CoV-2) in South African, Swiss and Tanzanian secondary schools. We estimated the risks of infection with the Wells-Riley equation, expressed as the median with 2.5% and 97.5% quantiles (credible interval [CrI]), based on the ventilation rate and the duration of exposure to infectious doses (so-called quanta). We computed the air change rate (ventilation) using carbon dioxide (CO2) as a tracer gas and modeled the quanta generation rate based on reported estimates from the literature. The share of infectious students in the classroom is determined by country-specific estimates of pulmonary TB. For SARS-CoV-2, the number of infectious students was estimated based on excess mortality to mitigate the bias from country-specific reporting and testing. Average CO2 concentration (parts per million [ppm]) was 1,610 ppm in South Africa, 1,757 ppm in Switzerland, and 648 ppm in Tanzania. The annual risk of infection for Mtb was 22.1% (interquartile range [IQR] 2.7%-89.5%) in South Africa, 0.7% (IQR 0.1%-6.4%) in Switzerland, and 0.5% (IQR 0.0%-3.9%) in Tanzania. For SARS-CoV-2, the monthly risk of infection was 6.8% (IQR 0.8%-43.8%) in South Africa, 1.2% (IQR 0.1%-8.8%) in Switzerland, and 0.9% (IQR 0.1%-6.6%) in Tanzania. The differences in transmission risks primarily reflect a higher incidence of SARS-CoV-2 and particularly prevalence of TB in South Africa, but also higher air change rates due to better natural ventilation of the classrooms in Tanzania. Global comparisons of the modeled risk of infectious disease transmission in classrooms can provide high-level information for policy-making regarding appropriate infection control strategies.
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Affiliation(s)
- Nicolas Banholzer
- Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland
| | - Remo Schmutz
- Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland
| | - Keren Middelkoop
- Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa
- Desmond Tutu Health Centre, Department of Medicine, University of Cape Town, Cape Town, South Africa
| | - Jerry Hella
- Ifakara Health Institute, Dar-es-Salaam, Tanzania
| | - Matthias Egger
- Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland
- Centre for Infectious Disease Epidemiology & Research, School of Public Health & Family Medicine, University of Cape Town, Cape Town, South Africa
- Population Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Robin Wood
- Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa
- Desmond Tutu Health Centre, Department of Medicine, University of Cape Town, Cape Town, South Africa
| | - Lukas Fenner
- Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland
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Kavanagh KT, Maiwald M, Pontus C, Cimiotti JP, Palmieri PA, Cormier LE. Frontline Worker Safety in the Age of COVID-19: A Global Perspective. J Patient Saf 2023; 19:293-299. [PMID: 37162150 PMCID: PMC10373843 DOI: 10.1097/pts.0000000000001132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The third annual Health Watch USA sm webinar conference assembled 16 speakers from 4 continents who shared information regarding frontline worker safety in the age of COVID-19. The U.S. Bureau of Labor Statistics reported a nearly 4000% increase in workplace illness in 2020 compared with 2019. It is estimated that 2% of the U.S. workforce is not working because of long COVID. In addition, the impact is growing with each surge. After the acute illness, patients are often described as recovered, when in fact many have only survived and are coping with the multisystem impacts of long COVID. Long COVID, including its late cognitive, cardiovascular, embolic, and diabetic complications, disproportionately impacts frontline workers, many of whom are of lower socioeconomic status and represented by ethnic minorities. Natural infection and current vaccines do not provide durable protection for reinfection. Herd immunity is not possible at this time. Although SARS-CoV-2 is unlikely to be eliminated, decreasing spread is imperative to slow the rate of mutations, decrease the number of reinfections, and lower the chances of developing long COVID. The primary mode of spread is through aerosolization. Both routine breathing and talking aerosolizes the virus. With the extremely high infectivity of SARS-CoV-2, it is unlikely that central building ventilation alone will be enough to satisfactorily mitigate spread. Additional safe active air cleaning technology, such as upper-room germicidal UV-C lighting, needs to be deployed. Misinformation and disinformation have inhibited response effectiveness. Examples include downplaying the benefit of well-fitted masks and the risks that COVID-19 and long COVID pose to children, along with believing children cannot spread the disease. The engagement of local community leaders is essential to educate the community and drive social change to accept vaccinations and other public health interventions. Vaccinations and natural immunity alone are unlikely to adequately prevent community spread and do not provide durable protection against the risk of long COVID. Frontline workers must keep their immunity as high as possible and work in settings with clean air, along with wearing N95 masks when they are in contact with the public. Finally, there needs to be a financial safety net for frontline workers and their families in the event of incapacitation or death from COVID-19.
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Affiliation(s)
| | - Matthias Maiwald
- KK Women’s and Children’s Hospital
- Yong Loo Lin School of Medicine, National University of Singapore
- Duke-National University of Singapore Graduate School of Medicine, Health Watch USA, Singapore
| | - Christine Pontus
- Massachusetts Nurses Association, United States, Health Watch USA Canton, Massachusetts
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A review on indoor airborne transmission of COVID-19– modelling and mitigation approaches. JOURNAL OF BUILDING ENGINEERING 2023; 64:105599. [PMCID: PMC9699823 DOI: 10.1016/j.jobe.2022.105599] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 11/11/2022] [Accepted: 11/21/2022] [Indexed: 06/09/2023]
Abstract
In the past few years, significant efforts have been made to investigate the transmission of COVID-19. This paper provides a review of the COVID-19 airborne transmission modeling and mitigation strategies. The simulation models here are classified into airborne transmission infectious risk models and numerical approaches for spatiotemporal airborne transmissions. Mathematical descriptions and assumptions on which these models have been based are discussed. Input data used in previous simulation studies to assess the dispersion of COVID-19 are extracted and reported. Moreover, measurements performed to study the COVID-19 airborne transmission within indoor environments are introduced to support validations for anticipated future modeling studies. Transmission mitigation strategies recommended in recent studies have been classified to include modifying occupancy and ventilation operations, using filters and air purifiers, installing ultraviolet (UV) air disinfection systems, and personal protection compliance, such as wearing masks and social distancing. The application of mitigation strategies to various building types, such as educational, office, public, residential, and hospital, is reviewed. Recommendations for future works are also discussed based on the current apparent knowledge gaps covering both modeling and mitigation approaches. Our findings show that different transmission mitigation measures were recommended for various indoor environments; however, there is no conclusive work reporting their combined effects on the level of mitigation that may be achieved. Moreover, further studies should be conducted to understand better the balance between approaches to mitigating the viral transmissions in buildings and building energy consumption.
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Della Marca R, Loy N, Tosin A. An SIR model with viral load-dependent transmission. J Math Biol 2023; 86:61. [PMID: 36973464 PMCID: PMC10042434 DOI: 10.1007/s00285-023-01901-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 02/01/2023] [Accepted: 03/11/2023] [Indexed: 03/29/2023]
Abstract
The viral load is known to be a chief predictor of the risk of transmission of infectious diseases. In this work, we investigate the role of the individuals' viral load in the disease transmission by proposing a new susceptible-infectious-recovered epidemic model for the densities and mean viral loads of each compartment. To this aim, we formally derive the compartmental model from an appropriate microscopic one. Firstly, we consider a multi-agent system in which individuals are identified by the epidemiological compartment to which they belong and by their viral load. Microscopic rules describe both the switch of compartment and the evolution of the viral load. In particular, in the binary interactions between susceptible and infectious individuals, the probability for the susceptible individual to get infected depends on the viral load of the infectious individual. Then, we implement the prescribed microscopic dynamics in appropriate kinetic equations, from which the macroscopic equations for the densities and viral load momentum of the compartments are eventually derived. In the macroscopic model, the rate of disease transmission turns out to be a function of the mean viral load of the infectious population. We analytically and numerically investigate the case that the transmission rate linearly depends on the viral load, which is compared to the classical case of constant transmission rate. A qualitative analysis is performed based on stability and bifurcation theory. Finally, numerical investigations concerning the model reproduction number and the epidemic dynamics are presented.
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Affiliation(s)
- Rossella Della Marca
- Mathematics Area, SISSA, International School for Advanced Studies, Via Bonomea 265, 34136 Trieste, Italy
| | - Nadia Loy
- Department of Mathematical Sciences “G. L. Lagrange”, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy
| | - Andrea Tosin
- Department of Mathematical Sciences “G. L. Lagrange”, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy
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11
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Morawska L, Marks GB, Monty J. Healthy indoor air is our fundamental need: the time to act is now. Med J Aust 2022; 217:578-581. [PMID: 36371692 PMCID: PMC10100118 DOI: 10.5694/mja2.51768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 09/14/2022] [Accepted: 09/21/2022] [Indexed: 11/15/2022]
Affiliation(s)
| | - Guy B Marks
- Woolcock Institute of Medical ResearchSydneyNSW
- Liverpool HospitalSydneyNSW
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12
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Rodríguez-Vidal I, Martín-Garín A, González-Quintial F, Rico-Martínez JM, Hernández-Minguillón RJ, Otaegi J. Response to the COVID-19 Pandemic in Classrooms at the University of the Basque Country through a User-Informed Natural Ventilation Demonstrator. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:14560. [PMID: 36361439 PMCID: PMC9658559 DOI: 10.3390/ijerph192114560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 10/30/2022] [Accepted: 11/04/2022] [Indexed: 06/16/2023]
Abstract
The COVID-19 pandemic has generated a renewed interest in indoor air quality to limit viral spread. In the case of educational spaces, due to the high concentration of people and the fact that most of the existing buildings do not have any mechanical ventilation system, the different administrations have established natural ventilation protocols to guarantee an air quality that reduces risk of contagion by the SARS-CoV-2 virus after the return to the classrooms. Many of the initial protocols established a ventilation pattern that opted for continuous or intermittent ventilation to varying degrees of intensity. This study, carried out on a university campus in Spain, analyses the performance of natural ventilation activated through the information provided by monitoring and visualisation of real-time data. In order to carry out this analysis, a experiment was set up where a preliminary study of ventilation without providing information to the users was carried out, which was then compared with the result of providing live feedback to the occupants of two classrooms and an administration office in different periods of 2020, 2021 and 2022. In the administration office, a CO2-concentration-based method was applied retrospectively to assess the risk of airborne infection. This experience has served as a basis to establish a route for user-informed improvement of air quality in educational spaces in general through low-cost systems that allow a rational use of natural ventilation while helping maintain an adequate compromise between IAQ, comfort and energy consumption, without having to resort to mechanical ventilation systems.
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Affiliation(s)
| | | | | | | | | | - Jorge Otaegi
- CAVIAR Research Group, Department of Architecture, University of the Basque Country UPV/EHU, Plaza Oñati, 2, 20018 Donostia-San Sebastián, Spain
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13
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Silva LFO, Li W, Moreno T. Introduction to the special issue on "COVID-19". GEOSCIENCE FRONTIERS 2022; 13:101403. [PMID: 37521132 PMCID: PMC9093084 DOI: 10.1016/j.gsf.2022.101403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 08/01/2023]
Affiliation(s)
- Luis F O Silva
- Department of Civil and Environmental, Universidad de la Costa, CUC, Calle 58 # 55-66, Barranquilla, Atlántico, Colombia
| | - Weijun Li
- Department of Atmospheric Sciences, School of Earth Sciences, Zhejiang University, China
| | - Teresa Moreno
- Institute for Environmental Assessment and Water Research, Consejo Superior de Investigaciones Científicas, 08028 Barcelona, Spain
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14
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Jimenez JL, Marr LC, Randall K, Ewing ET, Tufekci Z, Greenhalgh T, Tellier R, Tang JW, Li Y, Morawska L, Mesiano‐Crookston J, Fisman D, Hegarty O, Dancer SJ, Bluyssen PM, Buonanno G, Loomans MGLC, Bahnfleth WP, Yao M, Sekhar C, Wargocki P, Melikov AK, Prather KA. What were the historical reasons for the resistance to recognizing airborne transmission during the COVID-19 pandemic? INDOOR AIR 2022; 32:e13070. [PMID: 36040283 PMCID: PMC9538841 DOI: 10.1111/ina.13070] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 05/25/2022] [Accepted: 05/30/2022] [Indexed: 05/05/2023]
Abstract
The question of whether SARS-CoV-2 is mainly transmitted by droplets or aerosols has been highly controversial. We sought to explain this controversy through a historical analysis of transmission research in other diseases. For most of human history, the dominant paradigm was that many diseases were carried by the air, often over long distances and in a phantasmagorical way. This miasmatic paradigm was challenged in the mid to late 19th century with the rise of germ theory, and as diseases such as cholera, puerperal fever, and malaria were found to actually transmit in other ways. Motivated by his views on the importance of contact/droplet infection, and the resistance he encountered from the remaining influence of miasma theory, prominent public health official Charles Chapin in 1910 helped initiate a successful paradigm shift, deeming airborne transmission most unlikely. This new paradigm became dominant. However, the lack of understanding of aerosols led to systematic errors in the interpretation of research evidence on transmission pathways. For the next five decades, airborne transmission was considered of negligible or minor importance for all major respiratory diseases, until a demonstration of airborne transmission of tuberculosis (which had been mistakenly thought to be transmitted by droplets) in 1962. The contact/droplet paradigm remained dominant, and only a few diseases were widely accepted as airborne before COVID-19: those that were clearly transmitted to people not in the same room. The acceleration of interdisciplinary research inspired by the COVID-19 pandemic has shown that airborne transmission is a major mode of transmission for this disease, and is likely to be significant for many respiratory infectious diseases.
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Affiliation(s)
- Jose L. Jimenez
- Department of Chemistry and Cooperative Institute for Research in Environmental SciencesUniversity of ColoradoBoulderColoradoUSA
| | - Linsey C. Marr
- Department of Civil and Environmental EngineeringVirginia TechBlacksburgVirginiaUSA
| | | | | | - Zeynep Tufekci
- School of JournalismColumbia UniversityNew YorkNew YorkUSA
| | - Trish Greenhalgh
- Department of Primary Care Health SciencesMedical Sciences DivisionUniversity of OxfordOxfordUK
| | | | - Julian W. Tang
- Department of Respiratory SciencesUniversity of LeicesterLeicesterUK
| | - Yuguo Li
- Department of Mechanical EngineeringUniversity of Hong KongHong KongChina
| | - Lidia Morawska
- International Laboratory for Air Quality and HeathQueensland University of TechnologyBrisbaneQueenslandAustralia
| | | | - David Fisman
- Dalla Lana School of Public HealthUniversity of TorontoTorontoOntarioCanada
| | - Orla Hegarty
- School of Architecture, Planning & Environmental PolicyUniversity College DublinDublinIreland
| | - Stephanie J. Dancer
- Department of MicrobiologyHairmyres Hospital, Glasgow, and Edinburgh Napier UniversityGlasgowUK
| | - Philomena M. Bluyssen
- Faculty of Architecture and the Built EnvironmentDelft University of TechnologyDelftThe Netherlands
| | - Giorgio Buonanno
- Department of Civil and Mechanical EngineeringUniversity of Cassino and Southern LazioCassinoItaly
| | - Marcel G. L. C. Loomans
- Department of the Built EnvironmentEindhoven University of Technology (TU/e)EindhovenThe Netherlands
| | - William P. Bahnfleth
- Department of Architectural EngineeringThe Pennsylvania State UniversityUniversity ParkPennsylvaniaUSA
| | - Maosheng Yao
- College of Environmental Sciences and EngineeringPeking UniversityBeijingChina
| | - Chandra Sekhar
- Department of the Built EnvironmentNational University of SingaporeSingaporeSingapore
| | - Pawel Wargocki
- Department of Civil EngineeringTechnical University of DenmarkLyngbyDenmark
| | - Arsen K. Melikov
- Department of Civil EngineeringTechnical University of DenmarkLyngbyDenmark
| | - Kimberly A. Prather
- Scripps Institution of OceanographyUniversity of California San DiegoLa JollaCaliforniaUSA
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15
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Lunati I, Mucignat C. Infection risk in cable cars and other enclosed spaces. INDOOR AIR 2022; 32:e13094. [PMID: 36040286 PMCID: PMC9539082 DOI: 10.1111/ina.13094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/09/2022] [Revised: 06/10/2022] [Accepted: 07/15/2022] [Indexed: 06/15/2023]
Abstract
As virus-laden aerosols can accumulate and remain suspended for hours in insufficiently ventilated enclosed spaces, indoor environments can heavily contribute to the spreading of airborne infections. In the COVID-19 pandemics, the role possibly played by cable cars has attracted media attention following several outbreaks in ski resort. To assess the real risk of infection, we experimentally characterize the natural ventilation in cable cars and develop a general stochastic model of infection in an arbitrary indoor space that accounts for the epidemiological situation, the virological parameters, and the indoor characteristics (ventilation rate and occupant number density). As a results of the high air exchange rate (we measured up to 180 air changes per hour) and the relatively short duration of the journey, the infection probability in cable cars traveling with open windows is remarkably lower than in other enclosed spaces such as aircraft cabins, train cars, offices, classrooms, and dining rooms. Accounting for the typical duration of the stay, the probability of infection during a cable-car ride is lower by two to three orders of magnitude than in the other examples considered (the highest risk being estimated in case of a private gathering in a poorly ventilated room). For most practical purposes, the infection probability can be approximated by the inhaled viral dose, which provides an upper bound and allows a simple comparison between different indoor situations once the air exchange rate and the occupant number density are known. Our approach and findings are applicable to any indoor space in which the viral transmission is predominately airborne and the air is well mixed.
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Affiliation(s)
- Ivan Lunati
- Laboratory of Multiscale Studies in Building Physics, EmpaDübendorfSwitzerland
| | - Claudio Mucignat
- Laboratory of Multiscale Studies in Building Physics, EmpaDübendorfSwitzerland
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16
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Somsen GA, Winter MM, Tulevski II, Kooij S, Bonn D. Risk of aerosol transmission of SARS-CoV-2 in a clinical cardiology setting. BUILDING AND ENVIRONMENT 2022; 220:109254. [PMID: 35719131 PMCID: PMC9187860 DOI: 10.1016/j.buildenv.2022.109254] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 05/30/2022] [Accepted: 05/31/2022] [Indexed: 06/15/2023]
Abstract
Cardiac exercise stress testing (CEST) is an important diagnostic tool in daily cardiology practice. However, during intense physical activity microdroplet aerosols, potentially containing SARS-CoV-2 particles, can persist in a room for a long time. This poses a potential infection risk for the medical staff involved in CEST, as well as for the patients entering the same room afterwards. We measured aerosol generation and persistence, to perform a risk assessment for SARS-CoV-2 transmission through aerosols during CEST. We find that during CEST, the aerosol levels remain low enough that SARS-CoV-2 transmission through aerosols is unlikely, with the room ventilation system producing 14 air changes per hour. A simple measurement of CO2 concentration gives a good indication of the ventilation quality.
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Affiliation(s)
- G Aernout Somsen
- Cardiology Centers of the Netherlands, Amsterdam, the Netherlands
| | - Michiel M Winter
- Cardiology Centers of the Netherlands, Amsterdam, the Netherlands
- Amsterdam University Medical Centre, Amsterdam, the Netherlands
| | - Igor I Tulevski
- Cardiology Centers of the Netherlands, Amsterdam, the Netherlands
| | - Stefan Kooij
- Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam, the Netherlands
| | - Daniel Bonn
- Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam, the Netherlands
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17
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Aganovic A, Bi Y, Cao G, Kurnitski J, Wargocki P. Modeling the impact of indoor relative humidity on the infection risk of five respiratory airborne viruses. Sci Rep 2022; 12:11481. [PMID: 35798789 PMCID: PMC9261129 DOI: 10.1038/s41598-022-15703-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 06/28/2022] [Indexed: 11/09/2022] Open
Abstract
With a modified version of the Wells-Riley model, we simulated the size distribution and dynamics of five airborne viruses (measles, influenza, SARS-CoV-2, human rhinovirus, and adenovirus) emitted from a speaking person in a typical residential setting over a relative humidity (RH) range of 20-80% and air temperature of 20-25 °C. Besides the size transformation of virus-containing droplets due to evaporation, respiratory absorption, and then removal by gravitational settling, the modified model also considered the removal mechanism by ventilation. The trend and magnitude of RH impact depended on the respiratory virus. For rhinovirus and adenovirus humidifying the indoor air from 20/30 to 50% will be increasing the relative infection risk, however, this relative infection risk increase will be negligible for rhinovirus and weak for adenovirus. Humidification will have a potential benefit in decreasing the infection risk only for influenza when there is a large infection risk decrease for humidifying from 20 to 50%. Regardless of the dry solution composition, humidification will overall increase the infection risk via long-range airborne transmission of SARS-CoV-2. Compared to humidification at a constant ventilation rate, increasing the ventilation rate to moderate levels 0.5 → 2.0 h-1 will have a more beneficial infection risk decrease for all viruses except for influenza. Increasing the ventilation rate from low values of 0.5 h-1 to higher levels of 6 h-1 will have a dominating effect on reducing the infection risk regardless of virus type.
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Affiliation(s)
- Amar Aganovic
- Department of Automation and Process Engineering, The Arctic University of Norway-UiT, 9019, Tromsø, Norway.
| | - Yang Bi
- Department of Energy and Process Engineering, Norwegian University of Science and Technology-NTNU, 7491, Trondheim, Norway
| | - Guangyu Cao
- Department of Energy and Process Engineering, Norwegian University of Science and Technology-NTNU, 7491, Trondheim, Norway
| | - Jarek Kurnitski
- REHVA Technology and Research Committee, Tallinn University of Technology, 19086, Tallinn, Estonia
| | - Pawel Wargocki
- Department of Civil Engineering, Technical University of Denmark, 2800, Copenhagen, Kgs, Denmark
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18
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Rowe BR, Canosa A, Meslem A, Rowe F. Increased airborne transmission of COVID-19 with new variants, implications for health policies. BUILDING AND ENVIRONMENT 2022; 219:109132. [PMID: 35578697 PMCID: PMC9095081 DOI: 10.1016/j.buildenv.2022.109132] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 04/19/2022] [Accepted: 04/20/2022] [Indexed: 06/15/2023]
Abstract
New COVID-19 variants, either of higher viral load such as delta or higher contagiousness like omicron, can lead to higher airborne transmission than historical strains. This paper highlights their implications for health policies, based on a clear analytical understanding and modeling of the airborne contamination paths, of the dose following exposure, and the importance of the counting unit for pathogens, itself linked to the dose-response law. Using the counting unit of Wells, i.e. the quantum of contagium, we develop the conservation equation of quanta which allows deriving the value of the quantum concentration at steady state for a well-mixed room. The link with the monitoring concentration of carbon dioxide is made and used for a risk analysis of a variety of situations for which we collected CO2 time-series observations. The main conclusions of these observations are that 1) the present norms of ventilation, are both insufficient and not respected, especially in a variety of public premises, leading to high risk of contamination and that 2) air can often be considered well-mixed. Finally, we insist that public health policy in the field of airborne transmission should be based on a multi parameter analysis such as the time of exposure, the quantum production rate, mask wearing and the infector proportion in the population in order to evaluate the risk, considering the whole complexity of dose evaluation. Recognizing airborne transmission requires thinking in terms of time of exposure rather than in terms of proximal distance.
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Affiliation(s)
- Bertrand R Rowe
- Rowe Consulting, 22 chemin des moines, 22750 Saint Jacut de la Mer, France
| | - André Canosa
- CNRS, IPR (Institut de Physique de Rennes)-UMR 6251, Université de Rennes, 35000 Rennes, France
| | - Amina Meslem
- Université de Rennes, LGCGM, 3 Rue du Clos Courtel, BP 90422, 35704, Rennes, CEDEX 7, France
| | - Frantz Rowe
- Nantes Université, LEMNA, Nantes, France
- SKEMA Business School, KTO, Sophia-Antipolis, France
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19
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Prentiss M, Chu A, Berggren KK. Finding the infectious dose for COVID-19 by applying an airborne-transmission model to superspreader events. PLoS One 2022; 17:e0265816. [PMID: 35679278 PMCID: PMC9182663 DOI: 10.1371/journal.pone.0265816] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 03/08/2022] [Indexed: 12/19/2022] Open
Abstract
We probed the transmission of COVID-19 by applying an airborne transmission model to five well-documented case studies-a Washington state church choir, a Korean call center, a Korean exercise class, and two different Chinese bus trips. For all events the likely index patients were pre-symptomatic or mildly symptomatic, which is when infective patients are most likely to interact with large groups of people. Applying the model to those events yields results that suggest the following: (1) transmission was airborne; (2) superspreading events do not require an index patient with an unusually high viral load; (3) the viral loads for all of the index patients were of the same order of magnitude and consistent with experimentally measured values for patients at the onset of symptoms, even though viral loads across the population vary by a factor of >108. In particular we used a Wells-Riley exposure model to calculate q, the total average number of infectious quanta inhaled by a person at the event. Given the q value for each event, the simple airborne transmission model was used to determined Sq, the rate at which the index patient exhaled infectious quanta and N0, the characteristic number of COVID-19 virions needed to induce infection. Despite the uncertainties in the values of some parameters of the superspreading events, all five events yielded (N0∼300-2,000 virions), which is similar to published values for influenza. Finally, this work describes the conditions under which similar methods can provide actionable information on the transmission of other viruses.
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Affiliation(s)
- Mara Prentiss
- Department of Physics, Harvard University, Cambridge, MA, United States of America
| | - Arthur Chu
- QVT Family Office, New York, NY, United States of America
| | - Karl K. Berggren
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States of America
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20
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Jimenez JL, Peng Z, Pagonis D. Systematic way to understand and classify the shared-room airborne transmission risk of indoor spaces. INDOOR AIR 2022; 32:e13025. [PMID: 35622715 DOI: 10.1111/ina.13025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 03/16/2022] [Accepted: 03/17/2022] [Indexed: 05/22/2023]
Affiliation(s)
- Jose L Jimenez
- Department of Chemistry and CIRES, University of Colorado, Boulder, Colorado, USA
| | - Zhe Peng
- Department of Chemistry and CIRES, University of Colorado, Boulder, Colorado, USA
| | - Demetrios Pagonis
- Department of Chemistry and CIRES, University of Colorado, Boulder, Colorado, USA
- Department of Chemistry and Biochemistry, Weber State University, Ogden, Utah, USA
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21
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Buonanno G, Robotto A, Brizio E, Morawska L, Civra A, Corino F, Lembo D, Ficco G, Stabile L. Link between SARS-CoV-2 emissions and airborne concentrations: Closing the gap in understanding. JOURNAL OF HAZARDOUS MATERIALS 2022; 428:128279. [PMID: 35063838 PMCID: PMC8760841 DOI: 10.1016/j.jhazmat.2022.128279] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 01/11/2022] [Accepted: 01/12/2022] [Indexed: 05/03/2023]
Abstract
The airborne transmission of SARS-CoV-2 remains surprisingly controversial; indeed, health and regulatory authorities still require direct proof of this mode of transmission. To close this gap, we measured the viral load of SARS-CoV-2 of an infected subject in a hospital room (through an oral and nasopharyngeal swab), as well as the airborne SARS-CoV-2 concentration in the room resulting from the person breathing and speaking. Moreover, we simulated the same scenarios to estimate the concentration of RNA copies in the air through a novel theoretical approach and conducted a comparative analysis between experimental and theoretical results. Results showed that for an infected subject's viral load ranging between 2.4 × 106 and 5.5 × 106 RNA copies mL-1, the corresponding airborne SARS-CoV-2 concentration was below the minimum detection threshold when the person was breathing, and 16.1 (expanded uncertainty of 32.8) RNA copies m-3 when speaking. The application of the predictive approach provided concentrations metrologically compatible with the available experimental data (i.e. for speaking activity). Thus, the study presented significant evidence to close the gap in understanding airborne transmission, given that the airborne SARS-CoV-2 concentration was shown to be directly related to the SARS-CoV-2 emitted. Moreover, the theoretical analysis was shown to be able to quantitatively link the airborne concentration to the emission.
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Affiliation(s)
- G Buonanno
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy; International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Qld, Australia; Infectious Diseases Unit, Department of Medical Sciences, Amedeo di Savoia Hospital, University of Turin, Torino, Italy
| | - A Robotto
- Environmental Protection Agency of Piedmont (ARPA Piemonte), Italy; Infectious Diseases Unit, Department of Medical Sciences, Amedeo di Savoia Hospital, University of Turin, Torino, Italy
| | - E Brizio
- Environmental Protection Agency of Piedmont (ARPA Piemonte), Italy; Infectious Diseases Unit, Department of Medical Sciences, Amedeo di Savoia Hospital, University of Turin, Torino, Italy
| | - L Morawska
- International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Qld, Australia; Infectious Diseases Unit, Department of Medical Sciences, Amedeo di Savoia Hospital, University of Turin, Torino, Italy
| | - A Civra
- Dept. of Clinical and Biological Science, Azienda Ospedaliero-Universitaria San Luigi Gonzaga, University of Turin, Italy; Infectious Diseases Unit, Department of Medical Sciences, Amedeo di Savoia Hospital, University of Turin, Torino, Italy
| | - F Corino
- Environmental Protection Agency of Piedmont (ARPA Piemonte), Italy; Infectious Diseases Unit, Department of Medical Sciences, Amedeo di Savoia Hospital, University of Turin, Torino, Italy
| | - D Lembo
- Dept. of Clinical and Biological Science, Azienda Ospedaliero-Universitaria San Luigi Gonzaga, University of Turin, Italy; Infectious Diseases Unit, Department of Medical Sciences, Amedeo di Savoia Hospital, University of Turin, Torino, Italy
| | - G Ficco
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy; Infectious Diseases Unit, Department of Medical Sciences, Amedeo di Savoia Hospital, University of Turin, Torino, Italy
| | - L Stabile
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy; Infectious Diseases Unit, Department of Medical Sciences, Amedeo di Savoia Hospital, University of Turin, Torino, Italy.
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22
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Henriques A, Mounet N, Aleixo L, Elson P, Devine J, Azzopardi G, Andreini M, Rognlien M, Tarocco N, Tang J. Modelling airborne transmission of SARS-CoV-2 using CARA: risk assessment for enclosed spaces. Interface Focus 2022; 12:20210076. [PMID: 35261732 PMCID: PMC8831086 DOI: 10.1098/rsfs.2021.0076] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Accepted: 12/19/2021] [Indexed: 12/18/2022] Open
Abstract
The COVID-19 pandemic has highlighted the need for a proper risk assessment of respiratory pathogens in indoor settings. This paper documents the COVID Airborne Risk Assessment methodology, to assess the potential exposure of airborne SARS-CoV-2 viruses, with an emphasis on virological and immunological factors in the quantification of the risk. The model results from a multidisciplinary approach linking physical, mechanical and biological domains, enabling decision makers or facility managers to assess their indoor setting. The model was benchmarked against clinical data, as well as two real-life outbreaks, showing good agreement. A probability of infection is computed in several everyday-life settings and with various mitigation measures. The importance of super-emitters in airborne transmission is confirmed: 20% of infected hosts can emit approximately two orders of magnitude more viral-containing particles. The use of masks provides a fivefold reduction in viral emissions. Natural ventilation strategies are very effective to decrease the concentration of virions, although periodic venting strategies are not ideal in certain settings. Although vaccination is an effective measure against hospitalization, their effectiveness against transmission is not optimal, hence non-pharmaceutical interventions (ventilation, masks) should be actively supported. We also propose a critical threshold to define an acceptable risk level.
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Affiliation(s)
- Andre Henriques
- CERN (European Organization for Nuclear Research), Geneva, Switzerland
| | - Nicolas Mounet
- CERN (European Organization for Nuclear Research), Geneva, Switzerland
| | - Luis Aleixo
- CERN (European Organization for Nuclear Research), Geneva, Switzerland
| | - Philip Elson
- CERN (European Organization for Nuclear Research), Geneva, Switzerland
| | - James Devine
- CERN (European Organization for Nuclear Research), Geneva, Switzerland
| | | | - Marco Andreini
- CERN (European Organization for Nuclear Research), Geneva, Switzerland
| | - Markus Rognlien
- NTNU (Norwegian University of Science and Technology), Torgarden, Norway
| | - Nicola Tarocco
- CERN (European Organization for Nuclear Research), Geneva, Switzerland
| | - Julian Tang
- Respiratory Sciences, University of Leicester, Leicester, UK
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23
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Ding S, Lee JS, Mohamed MA, Ng BF. Infection risk of SARS-CoV-2 in a dining setting: Deposited droplets and aerosols. BUILDING AND ENVIRONMENT 2022; 213:108888. [PMID: 35169378 PMCID: PMC8828387 DOI: 10.1016/j.buildenv.2022.108888] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 02/01/2022] [Accepted: 02/08/2022] [Indexed: 05/06/2023]
Abstract
Considering that safe-distancing and mask-wearing measures are not strictly enforced in dining settings in the context of SARS-CoV-2, the infection risks of patrons in a dining outlet (e.g., a cafe) is assessed in this study. The size-resolved aerosol emission rate (AER) and droplets deposition rate (DDR) on dining plates from speaking were obtained through chamber measurements and droplet deposition visualization via fluorescent imaging technique (FIT), respectively. The AER from speaking was 24698 #/min in the size range of 0.3-5.5 μm, while the DDR was 365 #/min in the size range of 43-2847 μm. Furthermore, an infection risk model was adopted and revised to evaluate the infection risk of 120 diners for a "3-h event" in the cafe. In a four-person dining setting around a rectangular table, a diner seated diagonally across an infected person posed the least infection risk due to the deposited droplets on dining plates. The deposited droplets on a dining plate were dominant in possible viral transmission as compared to the long-range airborne route when a diner shared a table with the infected person. Yet, long-range airborne transmission had the potential to infect other diners in the cafe, even resulting in super-spreading events. A fresh air supply of 12.1-17.0 L/s per person is recommended for the cafe to serve 4-20 diners concurrently to minimize infection risks due to aerosols. Current ventilation standards (e.g., 8-10 L/s per person) for a cafe are not enough to avoid the airborne transmission of SARS-CoV-2.
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Affiliation(s)
- Shirun Ding
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore
| | - Jia Shing Lee
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore
| | - Mohamed Arif Mohamed
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore
| | - Bing Feng Ng
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore
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24
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Arpino F, Grossi G, Cortellessa G, Mikszewski A, Morawska L, Buonanno G, Stabile L. Risk of SARS-CoV-2 in a car cabin assessed through 3D CFD simulations. INDOOR AIR 2022; 32:e13012. [PMID: 35347787 PMCID: PMC9111293 DOI: 10.1111/ina.13012] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 02/09/2022] [Accepted: 02/18/2022] [Indexed: 05/26/2023]
Abstract
In this study, the risk of infection from SARS-CoV-2 Delta variant of passengers sharing a car cabin with an infected subject for a 30-min journey is estimated through an integrated approach combining a recently developed predictive emission-to-risk approach and a validated CFD numerical model numerically solved using the open-source OpenFOAM software. Different scenarios were investigated to evaluate the effect of the infected subject position within the car cabin, the airflow rate of the HVAC system, the HVAC ventilation mode, and the expiratory activity (breathing vs. speaking). The numerical simulations here performed reveal that the risk of infection is strongly influenced by several key parameters: As an example, under the same ventilation mode and emitting scenario, the risk of infection ranges from zero to roughly 50% as a function of the HVAC flow rate. The results obtained also demonstrate that (i) simplified zero-dimensional approaches limit proper evaluation of the risk in such confined spaces, conversely, (ii) CFD approaches are needed to investigate the complex fluid dynamics in similar indoor environments, and, thus, (iii) the risk of infection in indoor environments characterized by fixed seats can be in principle controlled by properly designing the flow patterns of the environment.
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Affiliation(s)
- Fausto Arpino
- Department of Civil and Mechanical EngineeringUniversity of Cassino and Southern LazioCassinoFRItaly
| | - Giorgio Grossi
- Department of Civil and Mechanical EngineeringUniversity of Cassino and Southern LazioCassinoFRItaly
| | - Gino Cortellessa
- Department of Civil and Mechanical EngineeringUniversity of Cassino and Southern LazioCassinoFRItaly
| | - Alex Mikszewski
- International Laboratory for Air Quality and HealthQueensland University of TechnologyBrisbaneQueenslandAustralia
| | - Lidia Morawska
- International Laboratory for Air Quality and HealthQueensland University of TechnologyBrisbaneQueenslandAustralia
| | - Giorgio Buonanno
- Department of Civil and Mechanical EngineeringUniversity of Cassino and Southern LazioCassinoFRItaly
- International Laboratory for Air Quality and HealthQueensland University of TechnologyBrisbaneQueenslandAustralia
| | - Luca Stabile
- Department of Civil and Mechanical EngineeringUniversity of Cassino and Southern LazioCassinoFRItaly
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25
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Peng Z, Rojas ALP, Kropff E, Bahnfleth W, Buonanno G, Dancer SJ, Kurnitski J, Li Y, Loomans MGLC, Marr LC, Morawska L, Nazaroff W, Noakes C, Querol X, Sekhar C, Tellier R, Greenhalgh T, Bourouiba L, Boerstra A, Tang JW, Miller SL, Jimenez JL. Practical Indicators for Risk of Airborne Transmission in Shared Indoor Environments and Their Application to COVID-19 Outbreaks. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:1125-1137. [PMID: 34985868 DOI: 10.1021/acs.est.1c06531] [Citation(s) in RCA: 60] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Some infectious diseases, including COVID-19, can undergo airborne transmission. This may happen at close proximity, but as time indoors increases, infections can occur in shared room air despite distancing. We propose two indicators of infection risk for this situation, that is, relative risk parameter (Hr) and risk parameter (H). They combine the key factors that control airborne disease transmission indoors: virus-containing aerosol generation rate, breathing flow rate, masking and its quality, ventilation and aerosol-removal rates, number of occupants, and duration of exposure. COVID-19 outbreaks show a clear trend that is consistent with airborne infection and enable recommendations to minimize transmission risk. Transmission in typical prepandemic indoor spaces is highly sensitive to mitigation efforts. Previous outbreaks of measles, influenza, and tuberculosis were also assessed. Measles outbreaks occur at much lower risk parameter values than COVID-19, while tuberculosis outbreaks are observed at higher risk parameter values. Because both diseases are accepted as airborne, the fact that COVID-19 is less contagious than measles does not rule out airborne transmission. It is important that future outbreak reports include information on masking, ventilation and aerosol-removal rates, number of occupants, and duration of exposure, to investigate airborne transmission.
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Affiliation(s)
- Z Peng
- Dept. of Chemistry and CIRES, University of Colorado, Boulder, Colorado 80309, United States
| | - A L Pineda Rojas
- CIMA, UMI-IFAECI/CNRS, FCEyN, Universidad de Buenos Aires─UBA/CONICET, Buenos Aires C1428EGA, Argentina
| | - E Kropff
- Leloir Institute─IIBBA/CONICET, CBA, Buenos Aires C1405BWE, Argentina
| | - W Bahnfleth
- Dept. of Architectural Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - G Buonanno
- Dept. of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino 03043, Italy
| | - S J Dancer
- Dept. of Microbiology, NHS Lanarkshire, Glasgow, Scotland G75 8RG, U.K
- School of Applied Sciences, Edinburgh Napier University, Edinburgh, Scotland EH11 4BN, U.K
| | - J Kurnitski
- REHVA Technology and Research Committee, Tallinn University of Technology, Tallinn 19086, Estonia
| | - Y Li
- Dept. of Mechanical Engineering, The University of Hong Kong, Hong Kong 999077, China
| | - M G L C Loomans
- Dept. of the Built Environment, Eindhoven University of Technology, Eindhoven 5612 AZ, The Netherlands
| | - L C Marr
- Dept. of Civil and Environmental Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - L Morawska
- International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Queensland 4001, Australia
| | - W Nazaroff
- Dept. of Civil and Environmental Engineering, University of California, Berkeley, California 94720, United States
| | - C Noakes
- School of Civil Engineering, University of Leeds, Leeds LS2 9JT, U.K
| | - X Querol
- Institute of Environmental Assessment and Water Research, IDAEA, Spanish Research Council, CSIC, Barcelona 08034, Spain
| | - C Sekhar
- Dept. of the Built Environment, National University of Singapore , 117566 Singapore
| | - R Tellier
- Dept. of Medicine, McGill University and McGill University Health Centre, Montreal, Québec H4A 3J1, Canada
| | - T Greenhalgh
- Nuffield Dept. of Primary Care Health Sciences, University of Oxford, Oxford OX2 6GG, U.K
| | - L Bourouiba
- The Fluid Dynamics of Disease Transmission Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - A Boerstra
- REHVA (Federation of European Heating, Ventilation and Air Conditioning Associations), BBA Binnenmilieu, The Hague 2501 CJ, The Netherlands
| | - J W Tang
- Dept. of Respiratory Sciences, University of Leicester, Leicester LE1 7RH, U.K
| | - S L Miller
- Dept. of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309, United States
| | - J L Jimenez
- Dept. of Chemistry and CIRES, University of Colorado, Boulder, Colorado 80309, United States
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