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 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 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 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 Aerosolization of Mycotoxins after Growth of Toxinogenic Fungi on Wallpaper

2017 ◽  
Vol 83 (16) ◽  
Author(s):  
Brankica Aleksic ◽  
Marjorie Draghi ◽  
Sebastien Ritoux ◽  
Sylviane Bailly ◽  
Marlène Lacroix ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Respiratory Tract ◽  
Building Material ◽  
Real Life ◽  
Indoor Environments ◽  
Air Velocity ◽  
Human Respiratory Tract ◽  
Content Type ◽  
Macrocyclic Trichothecenes ◽  
Toxic Load

ABSTRACT Many fungi can develop on building material in indoor environments if the moisture level is high enough. Among species that are frequently observed, some are known to be potent mycotoxin producers. This presence of toxinogenic fungi in indoor environments raises the question of the possible exposure of occupants to these toxic compounds by inhalation after aerosolization. This study investigated mycotoxin production by Penicillium brevicompactum, Aspergillus versicolor, and Stachybotrys chartarum during their growth on wallpaper and the possible subsequent aerosolization of produced mycotoxins from contaminated substrates. We demonstrated that mycophenolic acid, sterigmatocystin, and macrocyclic trichothecenes (sum of 4 major compounds) could be produced at levels of 1.8, 112.1, and 27.8 mg/m2, respectively, on wallpaper. Moreover, part of the produced toxins could be aerosolized from the substrate. The propensity for aerosolization differed according to the fungal species. Thus, particles were aerosolized from wallpaper contaminated with P. brevicompactum when an air velocity of just 0.3 m/s was applied, whereas S. chartarum required an air velocity of 5.9 m/s. A. versicolor was intermediate, since aerosolization occurred under an air velocity of 2 m/s. Quantification of the toxic content revealed that toxic load was mostly associated with particles of size ≥3 μm, which may correspond to spores. However, some macrocyclic trichothecenes (especially satratoxin H and verrucarin J) can also be found on smaller particles that can deeply penetrate the respiratory tract upon inhalation. These elements are important for risk assessment related to moldy environments. IMPORTANCE The possible colonization of building material by toxinogenic fungi in cases of moistening raises the question of the subsequent exposure of occupants to aerosolized mycotoxins. In this study, we demonstrated that three different toxinogenic species produce mycotoxins during their development on wallpaper. These toxins can subsequently be aerosolized, at least partly, from moldy material. This transfer to air requires air velocities that can be encountered under real-life conditions in buildings. Most of the aerosolized toxic load is found in particles whose size corresponds to spores or mycelium fragments. However, some toxins were also found on particles smaller than spores that are easily respirable and can deeply penetrate the human respiratory tract. All of these data are important for risk assessment related to fungal contamination of indoor environments.

Regional Relative Risk, a Physics-Based Metric for Characterizing Airborne Infectious Disease Transmission

2021 ◽  
Author(s):  
Michael B Dillon ◽  
Charles F Dillon
Keyword(s):  
Infectious Disease ◽  
Relative Risk ◽  
Disease Transmission ◽  
Spatial Scales ◽  
Disease Outbreaks ◽  
Indoor Environments ◽  
Infectious Disease Transmission ◽  
Wide Range ◽  
Risk Metric ◽  
Airborne Disease

Airborne infectious disease transmission events occur over a wide range of spatial scales and can be an important means of disease transmission. Physics- and biology- based models can assist in predicting airborne transmission events, overall disease incidence, and disease control strategy efficacy. We develop a new theory that extends current approaches for the case in which an individual is infected by a single airborne particle, including the scenario in which numerous infectious particles are present in the air but only one causes infection. A single infectious particle can contain more than one pathogenic microorganism and be physically larger than the pathogen itself. This approach allows robust relative risk estimates even when there is wide variation in (a) individual exposures and (b) the individual response to that exposure (the pathogen dose-response function can take any mathematical form and vary by individual). Based on this theory, we propose the Regional Relative Risk – a new metric, distinct from the traditional relative risk metric, that compares the risk between two regions (in theory, these regions can range from individual rooms to large geographic areas). In this paper, we apply the Regional Relative Risk metric to outdoor disease transmission events over spatial scales ranging from 50 m to 20 km demonstrating that in many common cases, minimal input information is required to use the metric. Also, we demonstrate that it is consistent with data from prior outbreaks. Future efforts could apply and validate this theory for other spatial scales, such as indoor environments. This work provides context for (a) the initial stages of an airborne disease outbreak and (b) larger scale disease spread, including unexpected low probability disease “sparks” that potentially affect remote populations, a key practical issue in controlling airborne disease outbreaks. Importance Airborne infectious disease transmission events occur over a wide range of spatial scales and can be important to disease outbreaks. We develop a new physics- and biology- based theory for the important case in which individuals are infected by a single airborne particle (numerous infectious particles can be emitted into the air and inhaled). Based on this theory, we propose a new epidemiological metric, Regional Relative Risk, that compares the risk between two geographic regions (in theory, regions can range from individual rooms to large areas). Our modeling of outdoors transmission events predicts that for many scenarios of interest, minimal information is required to use this metric for locations 50 m to 20 km downwind. This prediction is consistent with data from prior disease outbreaks. Future efforts could apply and validate this theory for other spatial scales, such as indoor environments. Our results may a priori be applicable to many airborne diseases as these results depend on the physics of airborne particulate dispersion.

Risk assessment of Campylobacter species in shellfish: identifying the unknown

1997 ◽  
Vol 35 (11-12) ◽  
pp. 29-34 ◽  
Author(s):  
P. Teunis ◽  
A. Havelaar ◽  
J. Vliegenthart ◽  
G. Roessink
Keyword(s):  
Risk Assessment ◽  
Quantitative Risk Assessment ◽  
Contamination Level ◽  
Risk Of Infection ◽  
Worst Case ◽  
Considerable Uncertainty ◽  
Risk Estimates ◽  
Consumption Data ◽  
Campylobacter Infection ◽  
Campylobacter Spp

Shellfish are frequently contaminated by Campylobacter spp, presumably originating from faeces from gulls feeding in the growing or relaying waters. The possible health effects of eating contaminated shellfish were estimated by quantitative risk assessment. A paucity of data was encountered necessitating many assumptions to complete the risk estimate. The level of Campylobacter spp in shellfish meat was calculated on the basis of a five-tube, single dilution MPN and was strongly season-dependent. The contamination level of mussels (<1/g) appeared to be higher than in oysters. The usual steaming process of mussels was found to completely inactivate Campylobacter spp so that risks are restricted to raw/undercooked shellfish. Consumption data were estimated on the basis of the usual size of a portion of raw shellfish and the weight of meat/individual animal. Using these data, season-dependent dose-distributions could be estimated. The dominant species in Dutch shellfish is C. lari but little is known on its infectivity for man. As a worst case assumption, it was assumed that the infectivity was similar to C. jejuni. A published dose-response model for Campylobacter-infection of volunteers is available but with considerable uncertainty in the low dose region. Using Monte Carlo simulation, risk estimates were constructed. The consumption of a single portion of raw shellfish resulted in a risk of infection of 5–20% for mussels (depending on season; 95% CI 0.01–60%). Repeated (e.g. monthly) exposures throughout a year resulted in an infection risk of 60% (95% CI 7–99%). Risks for oysters were slightly lower than for mussels. It can be concluded that, under the assumptions made, the risk of infection with Campylobacter spp by eating of raw shellfish is substantial. Quantitative risk estimates are highly demanding for the availability and quality of experimental data, and many research needs were identified.

scholarly journals Splatters and Aerosols Contamination in Dental Aerosol Generating Procedures

2021 ◽  
Vol 11 (4) ◽  
pp. 1914
Author(s):  
Pingping Han ◽  
Honghui Li ◽  
Laurence J. Walsh ◽  
Sašo Ivanovski
Keyword(s):  
Particle Size ◽  
Disease Transmission ◽  
High Speed ◽  
Low Speed ◽  
Dental Procedures ◽  
Dental Equipment ◽  
Produce Contamination ◽  
Fluorescein Dye ◽  
Filter Papers ◽  
Airborne Disease

Dental aerosol-generating procedures produce a large amount of splatters and aerosols that create a major concern for airborne disease transmission, such as COVID-19. This study established a method to visualise splatter and aerosol contamination by common dental instrumentation, namely ultrasonic scaling, air-water spray, high-speed and low-speed handpieces. Mock dental procedures were performed on a mannequin model, containing teeth in a typodont and a phantom head, using irrigation water containing fluorescein dye as a tracer. Filter papers were placed in 10 different locations to collect splatters and aerosols, at distances ranging from 20 to 120 cm from the source. All four types of dental equipment produced contamination from splatters and aerosols. At 120 cm away from the source, the high-speed handpiece generated the greatest amount and size (656 ± 551 μm) of splatter particles, while the triplex syringe generated the largest amount of aerosols (particle size: 1.73 ± 2.23 μm). Of note, the low-speed handpiece produced the least amount and size (260 ± 142 μm) of splatter particles and the least amount of aerosols (particle size: 4.47 ± 5.92 μm) at 120 cm. All four dental AGPs produce contamination from droplets and aerosols, with different patterns of distribution. This simple model provides a method to test various preventive strategies to reduce risks from splatter and aerosols.

scholarly journals Extended Lifetime of Respiratory Droplets in a Turbulent Vapor Puff and Its Implications on Airborne Disease Transmission

2021 ◽  
Vol 126 (3) ◽  
Author(s):  
Kai Leong Chong ◽  
Chong Shen Ng ◽  
Naoki Hori ◽  
Rui Yang ◽  
Roberto Verzicco ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Airborne Disease ◽  
Respiratory Droplets
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