scholarly journals A Computational Framework for Transmission Risk Assessment of Aerosolized Particles in Classrooms

2021 ◽  
Author(s):  
Kendrick Tan ◽  
Boshun Gao ◽  
Cheng-Hau Yang ◽  
Emily Johnson ◽  
Ming-Chen Hsu ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Disease Transmission ◽  
Ventilation Rate ◽  
Mitigation Strategies ◽  
Transmission Risk ◽  
Computational Framework ◽  
Seating Arrangement ◽  
K 12 ◽  
Education Administrators ◽  
Airborne Disease

Abstract The ongoing COVID-19 pandemic has rendered confined spaces as high-risk areas. There is an increasing push to resume in-person activities, for instance, teaching in K-12 and university settings. It becomes important to evaluate the risk of airborne disease transmission while accounting for the physical presence of humans, furniture, and electronic equipment, as well as ventilation. Here, we present a computational framework based on detailed flow physics simulations that allows straightforward evaluation of various seating and operating scenarios to identify risk factors and assess the effectiveness of various mitigation strategies. These scenarios include seating arrangement changes, presence/absence of computer screens, ventilation rate changes, and presence/absence of mask-wearing. This approach democratizes risk assessment by automating a key bottleneck in simulation-based analysis--creating an adequately refined mesh around multiple complex geometries. Not surprisingly, we find that wearing masks (with at least 74% inward protection efficiency) significantly reduced transmission risk against unmasked and infected individuals. The availability of such an analysis approach will allow education administrators, government officials (courthouses, police stations), and hospital administrators to make informed decisions on seating arrangements and operating procedures.

scholarly journals Assessment of Airborne Disease Transmission Risk and Energy Impact of HVAC Mitigation Strategies

2021 ◽  
Author(s):  
Michael J. Risbeck ◽  
Martin Z. Bazant ◽  
Zhanhong Jiang ◽  
Young M. Lee ◽  
Kirk H. Drees ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Significant Risk ◽  
Mitigation Strategies ◽  
Transmission Risk ◽  
Disease Spread ◽  
Particle Removal ◽  
Outdoor Air ◽  
Common Basis ◽  
Air Ventilation ◽  
Airborne Disease

The COVID-19 pandemic has focused renewed attention on the ways in which building HVAC systems may be operated to mitigate the risk of airborne disease transmission. The most common suggestion is to increase outdoor-air ventilation rates so as to dilute the concentrations of infectious aerosol particles indoors. Although this strategy does reduce the likelihood of disease spread, it is often much more costly than other strategies that provide equivalent particle removal or deactivation. To address this tradeoff and arrive at practical recommendations, we explain how different mitigation strategies can be expressed in terms of equivalent outdoor air (EOA) to provide a common basis for energy analysis. We then show the effects of each strategy on EOA delivery and energy cost in simulations of realistic buildings in a variety of climates. Key findings are that in-duct filtration is often the most efficient mitigation strategy, while significant risk reduction generally requires increasing total airflow to the system, either through adjusted HVAC setpoints or standalone disinfection devices.

scholarly journals Chronic Wasting Disease Transmission Risk Assessment for Farmed Cervids in Minnesota and Wisconsin

Viruses ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1586
Author(s):  
James M. Kincheloe ◽  
Dennis N. Makau ◽  
Scott J. Wells ◽  
Amy R. Horn-Delzer
Keyword(s):  
Risk Assessment ◽  
Disease Transmission ◽  
Chronic Wasting Disease ◽  
Control Measures ◽  
Transmission Risk ◽  
Effective Control ◽  
Wasting Disease ◽  
Qualitative Risk Assessment ◽  
Low Uncertainty ◽  
High Uncertainty

CWD (chronic wasting disease) has emerged as one of the most important diseases of cervids and continues to adversely affect farmed and wild cervid populations, despite control and preventive measures. This study aims to use the current scientific understanding of CWD transmission and knowledge of farmed cervid operations to conduct a qualitative risk assessment for CWD transmission to cervid farms and, applying this risk assessment, systematically describe the CWD transmission risks experienced by CWD-positive farmed cervid operations in Minnesota and Wisconsin. A systematic review of literature related to CWD transmission informed our criteria to stratify CWD transmission risks to cervid operations into high-risk low uncertainty, moderate-risk high uncertainty, and negligible-risk low uncertainty categories. Case data from 34 CWD-positive farmed cervid operations in Minnesota and Wisconsin from 2002 to January 2019 were categorized by transmission risks exposure and evaluated for trends. The majority of case farms recorded high transmission risks (56%), which were likely sources of CWD, but many (44%) had only moderate or negligible transmission risks, including most of the herds (62%) detected since 2012. The presence of CWD-positive cervid farms with only moderate or low CWD transmission risks necessitates further investigation of these risks to inform effective control measures.

scholarly journals Risk assessment and mitigation of airborne disease transmission in orchestral wind instrument performance

2021 ◽  
pp. 105797
Author(s):  
Aliza Abraham ◽  
Ruichen He ◽  
Siyao Shao ◽  
S. Santosh Kumar ◽  
Changchang Wang ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Disease Transmission ◽  
Instrument Performance ◽  
Wind Instrument ◽  
Airborne Disease

scholarly journals Beyond well-mixed: a simple probabilistic model of airborne disease transmission in indoor spaces

2021 ◽  
Author(s):  
Sijian Tan ◽  
Zhihang Zhang ◽  
Kevin Maki ◽  
Krzysztof J. Fidkowski ◽  
Jesse Capecelatro
Keyword(s):  
Disease Transmission ◽  
Risk Model ◽  
Ventilation Rate ◽  
Turbulent Dispersion ◽  
Balance Model ◽  
Wide Range ◽  
Ventilation Rates ◽  
Airborne Disease ◽  
Droplet Nuclei ◽  
Indoor Spaces

AbstractWe develop a simple model for assessing risk of airborne disease transmission that accounts for non-uniform mixing in indoor spaces and is compatible with existing epidemiological models. A database containing 174 high-resolution simulations of airflow in classrooms, lecture halls, and buses is generated and used to quantify the spatial distribution of expiratory droplet nuclei for a wide range of ventilation rates, exposure times, and room configurations. Imperfect mixing due to obstructions, buoyancy, and turbulent dispersion results in concentration fields with significant variance. The spatial non-uniformity is found to be accurately described by a shifted lognormal distribution. A well-mixed mass balance model is used to predict the mean, and the standard deviation is parameterized based on ventilation rate and room geometry. When employed in a dose-response function risk model, infection probability can be estimated considering spatial heterogeneity that contributes to both short- and long-range transmission.

scholarly journals Airflows inside passenger cars and implications for airborne disease transmission

2020 ◽  
Vol 7 (1) ◽  
pp. eabe0166 ◽  
Author(s):  
Varghese Mathai ◽  
Asimanshu Das ◽  
Jeffrey A. Bailey ◽  
Kenneth Breuer
Keyword(s):  
Disease Transmission ◽  
Respiratory Diseases ◽  
Passive Scalar ◽  
Elevated Risk ◽  
Pathogen Transmission ◽  
Transmission Risk ◽  
Residence Times ◽  
Passenger Cars ◽  
Complex Fluid ◽  
Airborne Disease

Transmission of highly infectious respiratory diseases, including SARS-CoV-2, is facilitated by the transport of exhaled droplets and aerosols that can remain suspended in air for extended periods of time. A passenger car cabin represents one such situation with an elevated risk of pathogen transmission. Here, we present results from numerical simulations to assess how the in-cabin microclimate of a car can potentially spread pathogenic species between occupants for a variety of open and closed window configurations. We estimate relative concentrations and residence times of a noninteracting, passive scalar—a proxy for infectious particles—being advected and diffused by turbulent airflows inside the cabin. An airflow pattern that travels across the cabin, farthest from the occupants, can potentially reduce the transmission risk. Our findings reveal the complex fluid dynamics during everyday commutes and nonintuitive ways in which open windows can either increase or suppress airborne transmission.

scholarly journals Risk assessment for airborne disease transmission by poly-pathogen aerosols

PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0248004
Author(s):  
Freja Nordsiek ◽  
Eberhard Bodenschatz ◽  
Gholamhossein Bagheri
Keyword(s):  
Risk Assessment ◽  
Respiratory Tract ◽  
Poisson Distribution ◽  
Disease Transmission ◽  
Indoor Environments ◽  
Dose Calculations ◽  
Risk Of Infection ◽  
Response Models ◽  
Airborne Disease ◽  
Aerosol Source

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.

scholarly journals Mitigation strategies for airborne disease transmission in orchestras using computational fluid dynamics

2021 ◽  
Vol 7 (26) ◽  
pp. eabg4511
Author(s):  
Hayden A. Hedworth ◽  
Mokbel Karam ◽  
Josh McConnell ◽  
James C. Sutherland ◽  
Tony Saad
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Disease Transmission ◽  
Performing Arts ◽  
Mitigation Strategies ◽  
Quantitative Microbial Risk Assessment ◽  
Breathing Zone ◽  
Microbial Risk Assessment ◽  
Microbial Risk ◽  
Airborne Disease

The COVID-19 pandemic forced performing arts groups to cancel shows and entire seasons due to safety concerns for the audience and performers. It is unclear to what extent aerosols generated by wind instruments contribute to exposure because their fate is dependent on the airflow onstage. We use transient, second-order accurate computational fluid dynamics (CFD) simulations and quantitative microbial risk assessment to estimate aerosol concentrations and the associated risk and assess strategies to mitigate exposure in two distinct concert venues. Mitigation strategies involved rearranging musicians and altering the airflow by changing HVAC settings, opening doors, and introducing flow-directing geometries. Our results indicate that the proposed mitigation strategies can reduce aerosol concentrations in the breathing zone by a factor of 100, corresponding to a similar decrease in the probability of infection.

scholarly journals Risk assessment for airborne disease transmission by poly-pathogen aerosols

2020 ◽  
Author(s):  
Freja Nordsiek ◽  
Eberhard Bodenschatz ◽  
Gholamhossein Bagheri
Keyword(s):  
Risk Assessment ◽  
Respiratory Tract ◽  
Poisson Distribution ◽  
Disease Transmission ◽  
Indoor Environments ◽  
Dose Calculations ◽  
Risk Of Infection ◽  
Response Models ◽  
Airborne Disease ◽  
Aerosol Source

AbstractIn the case of airborne diseases, pathogen copies are transmitted by droplets of respiratory tract fluid that are exhaled by the infectious 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.

scholarly journals Details of COVID-19 Disease Mitigation Strategies in 17 K-12 Schools in Wood County, Wisconsin

2021 ◽  
Author(s):  
Amy Falk ◽  
Alison Benda ◽  
Sarah Steffen ◽  
Mikaela DeCoster ◽  
Monica Gandhi ◽  
...  
Keyword(s):  
School Districts ◽  
Elementary Students ◽  
Secondary Students ◽  
Disease Transmission ◽  
Ventilation System ◽  
Mitigation Strategies ◽  
Disease Spread ◽  
Return To School ◽  
Full Time ◽  
K 12

Importance: With the current COVID-19 return to school guidelines, over half of American K-12 students are being denied access to full time in-person education, leading to harmful academic, emotional and health consequences. Objective: To describe the specific details of mitigation strategies employed at 17 K-12 schools in Wisconsin during a time of exceptionally high COVID-19 community disease prevalence where in-school transmission was minimal. The aim of this report is to assist school districts and governing bodies in developing full-time return to school plans. Design: Retrospective cohort Setting: Wood County, Wisconsin, August 31 to November 29, 2020 Participants: 5,530 students and staff from 17 schools in 4 school districts Main outcomes and measures: 1. Distancing between primary and secondary students in school 2. School ventilation details 3. Masking among teachers 4. Lunch, recess and bussing practices Results: 89.3% of elementary students included in our study did not maintain 6 feet of physical distancing in the classroom and 94.8% were within 6 feet in lunchrooms. The majority of secondary students (86.2%) were able to maintain 6 feet of distancing in the classroom but no students were greater than 6 feet in the hallways. 58.8% of schools did not install new ventilation systems prior to the school year. Students ate lunch indoors. Bussing of students continued and all elementary children were allowed to go without masks at recess. Conclusion and relevance: In the setting of high community COVID-19 disease transmission, 6 feet of distance between elementary students and major ventilation system renovations in primary or secondary schools do not appear to be necessary to minimize disease spread. Requiring masks at recess and prohibiting bussing also appears unnecessary. These findings may inform guidance on the safe reopening of schools and allow for more children to return to in-person schooling.

scholarly journals Far-UVC efficiently inactivates an airborne pathogen in a room-sized chamber

2021 ◽  
Author(s):  
Ewan Eadie ◽  
Waseem Hiwar ◽  
Louise Fletcher ◽  
Emma Tidswell ◽  
Paul O’Mahoney ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Environmental Control ◽  
Ventilation Rate ◽  
Control Measures ◽  
Delayed Effects ◽  
Pathogen Load ◽  
Regulatory Limits ◽  
Airborne Disease ◽  
Airborne Viruses ◽  
Scale Data

Abstract Many infectious diseases, including COVID-19, are transmitted by airborne pathogens. There is a need for effective environmental control measures which, ideally, are not reliant on human behaviour. One potential solution is Far-UVC which can efficiently inactivate pathogens, such as coronaviruses and influenza, in air. When appropriately filtered, and because of its limited penetration, there is evidence that Far-UVC does not induce acute reactions in the skin or eyes, nor delayed effects such as skin cancer. While there is laboratory evidence for far-UVC efficacy, there is limited evidence in full-sized rooms. In the first study of its type, we show that Far-UVC deployed in a room-sized chamber effectively inactivates aerosolised Staphylococcus aureus. At a room ventilation rate of 3 air changes per hour (ACH), with 5 filtered sources the steady-state pathogen load was reduced by 92.1% providing an additional 35 equivalent air changes (eACH). This reduction was achieved using Far-UVC intensities consistent with current regulatory limits. Far-UVC is likely to be more effective against common airborne viruses, including SARS-CoV-2, and should thus be an effective and “hands-off” technology to reduce airborne disease transmission. The findings provide room-scale data to support the design and development of safe and effective Far-UVC systems.

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