Aerosol Transmission of Viral Disease

A special issue of Viruses (ISSN 1999-4915). This special issue belongs to the section "General Virology".

Deadline for manuscript submissions: closed (30 June 2022) | Viewed by 56441

Special Issue Editors


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Guest Editor
Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE 68198, USA
Interests: bioaerosol measurement and detection; atmospheric chemistry of bioaerosols; bacteriophage; aerosol transmission of disease; viral aerosols

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Guest Editor
The Defence Science and Technology Laboratory (Dstl) Porton Down, Porton Down, Salisbury SP4 0JQ, UK
Interests: Infectious Disease Control and Prevention; Immunology of Infectious Diseases; Infectious Disease Epidemiology; aerosol transmission of viral disease

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Guest Editor
Department of Homeland Security, Science and Technology Directorate (DHS S&T), Noblis ESI, Reston, VA, USA
Interests: aerosolized infectious diseases

Special Issue Information

Dear Colleagues,

The study of airborne microorganisms and the role they play in human health and disease has been a field of research for many decades. The recent COVID-19 pandemic has spurred a large interest in the specific role of infectious aerosol particles in the transmission of airborne diseases. Viral aerosols are responsible for the transmission of several human diseases, including measles, smallpox, coronaviruses, and influenza, as well as diseases of plants and non-human animals. Anthropogenic activities such as improper ventilation, gathering in close quarters, and HVAC can impact the transport and infectivity of these aerosols from person-to-person creating avenues for the spread of disease in the built environment, and both indoor and outdoor air quality may impact both the stability of viral aerosols and the susceptibility of the host. In this Special Issue, we highlight new developments in understanding the role of viral aerosols in viral transport and transmission and prevention of future pandemics.

Dr. Joshua L. Santarpia
Dr. Mark Stephen Lever
Dr. Shanna A. Ratnesar-Shumate
Guest Editors

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Keywords

  • viral aerosols
  • infectious aerosols
  • COVID-19
  • airborne disease
  • anthropogenic impacts on the transmission of disease
  • the role of aerosols in animal viruses
  • the role of aerosols in plant viruses

Published Papers (16 papers)

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17 pages, 1893 KiB  
Article
The Role of Airborne Particles in the Epidemiology of Clade 2.3.4.4b H5N1 High Pathogenicity Avian Influenza Virus in Commercial Poultry Production Units
by Joe James, Caroline J. Warren, Dilhani De Silva, Thomas Lewis, Katherine Grace, Scott M. Reid, Marco Falchieri, Ian H. Brown and Ashley C. Banyard
Viruses 2023, 15(4), 1002; https://doi.org/10.3390/v15041002 - 19 Apr 2023
Cited by 4 | Viewed by 3565
Abstract
Since October 2021, Europe has experienced the largest avian influenza virus (AIV) epizootic, caused by clade 2.3.4.4b H5N1 high pathogenicity AIV (HPAIV), with over 284 poultry infected premises (IPs) and 2480 dead H5N1-positive wild birds detected in Great Britain alone. Many IPs have [...] Read more.
Since October 2021, Europe has experienced the largest avian influenza virus (AIV) epizootic, caused by clade 2.3.4.4b H5N1 high pathogenicity AIV (HPAIV), with over 284 poultry infected premises (IPs) and 2480 dead H5N1-positive wild birds detected in Great Britain alone. Many IPs have presented as geographical clusters, raising questions about the lateral spread between premises by airborne particles. Airborne transmission over short distances has been observed for some AIV strains. However, the risk of airborne spread of this strain remains to be elucidated. We conducted extensive sampling from IPs where clade 2.3.4.4b H5N1 HPAIVs were confirmed during the 2022/23 epizootic, each representing a major poultry species (ducks, turkeys, and chickens). A range of environmental samples were collected inside and outside houses, including deposited dust, feathers, and other potential fomites. Viral RNA (vRNA) and infectious viruses were detected in air samples collected from inside and outside but in close proximity to infected houses, with vRNA alone being detected at greater distances (≤10 m) outside. Some dust samples collected outside of the affected houses contained infectious viruses, while feathers from the affected houses, located up to 80 m away, only contained vRNA. Together, these data suggest that airborne particles harboring infectious HPAIV can be translocated short distances (<10 m) through the air, while macroscopic particles containing vRNA might travel further (≤80 m). Therefore, the potential for airborne transmission of clade 2.3.4.4b H5N1 HPAIV between premises is considered low. Other factors, including indirect contact with wild birds and the efficiency of biosecurity, represent greater importance in disease incursion. Full article
(This article belongs to the Special Issue Aerosol Transmission of Viral Disease)
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10 pages, 1230 KiB  
Article
Aerosol Survival, Disinfection and Formalin Inactivation of Nipah Virus
by Sophie J. Smither, Lin S. Eastaugh, Lyn M. O’Brien, Amanda L. Phelps and Mark S. Lever
Viruses 2022, 14(9), 2057; https://doi.org/10.3390/v14092057 - 16 Sep 2022
Cited by 2 | Viewed by 1898
Abstract
Nipah virus is a relatively newly discovered emerging virus on the WHO list of priority pathogens which has the potential to cause outbreaks with high fatality rates. Whilst progress is being made in the development of animal models for evaluating vaccines and therapies, [...] Read more.
Nipah virus is a relatively newly discovered emerging virus on the WHO list of priority pathogens which has the potential to cause outbreaks with high fatality rates. Whilst progress is being made in the development of animal models for evaluating vaccines and therapies, some of the more fundamental data on Nipah virus are lacking. We performed studies to generate novel information on the aerosol survival of Nipah virus and to look at the efficacy of two common disinfectants. We also performed studies to evaluate the inactivation of Nipah virus by using neutral buffered formalin. Nipah virus was relatively stable in a small particle (1–5 µm) aerosol in the dark, with it having a decay rate of 1.46%min−1. Sodium hypochlorite (at 10%) and ethanol (at 80%) reduced the titre of Nipah virus to undetectable levels. Nipah virus that was in tissue culture medium was also inactivated after 24 h in the presence of 10% formalin. Full article
(This article belongs to the Special Issue Aerosol Transmission of Viral Disease)
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13 pages, 2847 KiB  
Article
Mucin Transiently Sustains Coronavirus Infectivity through Heterogenous Changes in Phase Morphology of Evaporating Aerosol
by Robert W. Alexander, Jianghan Tian, Allen E. Haddrell, Henry P. Oswin, Edward Neal, Daniel A. Hardy, Mara Otero-Fernandez, Jamie F. S. Mann, Tristan A. Cogan, Adam Finn, Andrew D. Davidson, Darryl J. Hill and Jonathan P. Reid
Viruses 2022, 14(9), 1856; https://doi.org/10.3390/v14091856 - 24 Aug 2022
Cited by 9 | Viewed by 3061
Abstract
Respiratory pathogens can be spread though the transmission of aerosolised expiratory secretions in the form of droplets or particulates. Understanding the fundamental aerosol parameters that govern how such pathogens survive whilst airborne is essential to understanding and developing methods of restricting their dissemination. [...] Read more.
Respiratory pathogens can be spread though the transmission of aerosolised expiratory secretions in the form of droplets or particulates. Understanding the fundamental aerosol parameters that govern how such pathogens survive whilst airborne is essential to understanding and developing methods of restricting their dissemination. Pathogen viability measurements made using Controlled Electrodynamic Levitation and Extraction of Bioaerosol onto Substrate (CELEBS) in tandem with a comparative kinetics electrodynamic balance (CKEDB) measurements allow for a direct comparison between viral viability and evaporation kinetics of the aerosol with a time resolution of seconds. Here, we report the airborne survival of mouse hepatitis virus (MHV) and determine a comparable loss of infectivity in the aerosol phase to our previous observations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Through the addition of clinically relevant concentrations of mucin to the bioaerosol, there is a transient mitigation of the loss of viral infectivity at 40% RH. Increased concentrations of mucin promoted heterogenous phase change during aerosol evaporation, characterised as the formation of inclusions within the host droplet. This research demonstrates the role of mucus in the aerosol phase and its influence on short-term airborne viral stability. Full article
(This article belongs to the Special Issue Aerosol Transmission of Viral Disease)
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21 pages, 2252 KiB  
Article
Adapting an Atmospheric Dispersion Model to Assess the Risk of Windborne Transmission of Porcine Reproductive and Respiratory Syndrome Virus between Swine Farms
by Kaushi S. T. Kanankege, Kerryne Graham, Cesar A. Corzo, Kimberly VanderWaal, Andres M. Perez and Peter A. Durr
Viruses 2022, 14(8), 1658; https://doi.org/10.3390/v14081658 - 28 Jul 2022
Cited by 4 | Viewed by 1977
Abstract
Modeling the windborne transmission of aerosolized pathogens is challenging. We adapted an atmospheric dispersion model (ADM) to simulate the windborne dispersion of porcine reproductive and respiratory syndrome virus (PRRSv) between swine farms. This work focuses on determining ADM applicable parameter values for PRRSv [...] Read more.
Modeling the windborne transmission of aerosolized pathogens is challenging. We adapted an atmospheric dispersion model (ADM) to simulate the windborne dispersion of porcine reproductive and respiratory syndrome virus (PRRSv) between swine farms. This work focuses on determining ADM applicable parameter values for PRRSv through a literature and expert opinion-based approach. The parameters included epidemiological features of PRRSv, characteristics of the aerosolized particles, and survival of aerosolized virus in relation to key meteorological features. A case study was undertaken to perform a sensitivity analysis on key parameters. Farms experiencing ongoing PRRSv outbreaks were assigned as particle emitting sources. The wind data from the North American Mesoscale Forecast System was used to simulate dispersion. The risk was estimated semi-quantitatively based on the median daily deposition of particles and the distance to the closest emitting farm. Among the parameters tested, the ADM was most sensitive to the number of particles emitted, followed by the model runtime, and the release height was the least sensitive. Farms within 25 km from an emitting farm were at the highest risk; with 53.66% being within 10 km. An ADM-based risk estimation of windborne transmission of PRRSv may inform optimum time intervals for air sampling, plan preventive measures, and aid in ruling out the windborne dispersion in outbreak investigations. Full article
(This article belongs to the Special Issue Aerosol Transmission of Viral Disease)
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31 pages, 8617 KiB  
Article
A Novel Framework for Modeling Person-to-Person Transmission of Respiratory Diseases
by Jason Rodriguez, Owen Price, Rachel Jennings, Amy Creel, Sarah Eaton, Jennifer Chesnutt, Gene McClellan and Sweta R. Batni
Viruses 2022, 14(7), 1567; https://doi.org/10.3390/v14071567 - 19 Jul 2022
Viewed by 2017
Abstract
From the beginning of the COVID-19 pandemic, researchers assessed the impact of the disease in terms of loss of life, medical load, economic damage, and other key metrics of resiliency and consequence mitigation; these studies sought to parametrize the critical components of a [...] Read more.
From the beginning of the COVID-19 pandemic, researchers assessed the impact of the disease in terms of loss of life, medical load, economic damage, and other key metrics of resiliency and consequence mitigation; these studies sought to parametrize the critical components of a disease transmission model and the resulting analyses were informative but often lacked critical parameters or a discussion of parameter sensitivities. Using SARS-CoV-2 as a case study, we present a robust modeling framework that considers disease transmissibility from the source through transport and dispersion and infectivity. The framework is designed to work across a range of particle sizes and estimate the generation rate, environmental fate, deposited dose, and infection, allowing for end-to-end analysis that can be transitioned to individual and population health models. In this paper, we perform sensitivity analysis on the model framework to demonstrate how it can be used to advance and prioritize research efforts by highlighting critical parameters for further analyses. Full article
(This article belongs to the Special Issue Aerosol Transmission of Viral Disease)
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10 pages, 2588 KiB  
Communication
Impact of Chemical Properties of Human Respiratory Droplets and Aerosol Particles on Airborne Viruses’ Viability and Indoor Transmission
by Ajit Ahlawat, Sumit Kumar Mishra, Hartmut Herrmann, Pradhi Rajeev, Tarun Gupta, Vikas Goel, Yele Sun and Alfred Wiedensohler
Viruses 2022, 14(7), 1497; https://doi.org/10.3390/v14071497 - 8 Jul 2022
Cited by 4 | Viewed by 5916
Abstract
The airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been identified as a potential pandemic challenge, especially in poorly ventilated indoor environments, such as certain hospitals, schools, public buildings, and transports. The impacts of meteorological parameters (temperature and humidity) and [...] Read more.
The airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been identified as a potential pandemic challenge, especially in poorly ventilated indoor environments, such as certain hospitals, schools, public buildings, and transports. The impacts of meteorological parameters (temperature and humidity) and physical property (droplet size) on the airborne transmission of coronavirus in indoor settings have been previously investigated. However, the impacts of chemical properties of viral droplets and aerosol particles (i.e., chemical composition and acidity (pH)) on viability and indoor transmission of coronavirus remain largely unknown. Recent studies suggest high organic content (proteins) in viral droplets and aerosol particles supports prolonged survival of the virus by forming a glassy gel-type structure that restricts the virus inactivation process under low relative humidity (RH). In addition, the virus survival was found at neutral pH, and inactivation was observed to be best at low (<5) and high pH (>10) values (enveloped bacteriophage Phi6). Due to limited available information, this article illustrates an urgent need to research the impact of chemical properties of exhaled viral particles on virus viability. This will improve our fundamental understanding of indoor viral airborne transmission mechanisms. Full article
(This article belongs to the Special Issue Aerosol Transmission of Viral Disease)
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12 pages, 1085 KiB  
Article
Infectious Aerosol Capture Mask as Environmental Control to Reduce Spread of Respiratory Viral Particles
by Joshua L. Santarpia, Nicholas W. Markin, Vicki L. Herrera, Daniel N. Ackerman, Danielle N. Rivera, Gabriel A. Lucero and Steven J. Lisco
Viruses 2022, 14(6), 1275; https://doi.org/10.3390/v14061275 - 11 Jun 2022
Cited by 2 | Viewed by 1733
Abstract
Negative pressure isolation of COVID-19 patients is critical to limiting the nosocomial transmission of SARS-CoV-2; however, airborne isolation rooms are limited. Alternatives to traditional isolation procedures are needed. The evaluation of an Infectious Aerosol Capture Mask (IACM) that is designed to augment the [...] Read more.
Negative pressure isolation of COVID-19 patients is critical to limiting the nosocomial transmission of SARS-CoV-2; however, airborne isolation rooms are limited. Alternatives to traditional isolation procedures are needed. The evaluation of an Infectious Aerosol Capture Mask (IACM) that is designed to augment the respiratory isolation of COVID-19 patients is described. Efficacy in capturing exhaled breath aerosols was evaluated using laboratory experimentation, computational fluid dynamics (CFD) and measurements of exhaled breath from COVID-19 patients and their surroundings. Laboratory aerosol experiments indicated that the mask captured at least 99% of particles. Simulations of breathing and speaking showed that all particles between 0.1 and 20 µm were captured either on the surface of the mask or in the filter. During coughing, no more than 13% of the smallest particles escaped the mask, while the remaining particles collected on the surfaces or filter. The total exhaled virus concentrations of COVID-positive patients showed a range from undetectable to 1.1 × 106 RNA copies/h of SARS-CoV-2, and no SARS-CoV-2 aerosol was detected in the samples collected that were adjacent to the patient when the mask was being worn. These data indicate that the IACM is useful for containing the exhaled aerosol of infected individuals and can be used to quantify the viral aerosol production rates during respiratory activities. Full article
(This article belongs to the Special Issue Aerosol Transmission of Viral Disease)
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25 pages, 3588 KiB  
Article
Effect of Relative Humidity on Transfer of Aerosol-Deposited Artificial and Human Saliva from Surfaces to Artificial Finger-Pads
by Maurice D. Walker, Jack C. Vincent, Lee Benson, Corinne A. Stone, Guy Harris, Rachael E. Ambler, Pat Watts, Tom Slatter, Martín López-García, Marco-Felipe King, Catherine J. Noakes and Richard J. Thomas
Viruses 2022, 14(5), 1048; https://doi.org/10.3390/v14051048 - 15 May 2022
Cited by 6 | Viewed by 3410
Abstract
Surface to hand transfer of viruses represents a potential mechanism for human exposure. An experimental process for evaluating the touch transfer of aerosol-deposited material is described based on controlling surface, tribological, and soft matter components of the transfer process. A range of high-touch [...] Read more.
Surface to hand transfer of viruses represents a potential mechanism for human exposure. An experimental process for evaluating the touch transfer of aerosol-deposited material is described based on controlling surface, tribological, and soft matter components of the transfer process. A range of high-touch surfaces were evaluated. Under standardized touch parameters (15 N, 1 s), relative humidity (RH) of the atmosphere around the contact transfer event significantly influenced transfer of material to the finger-pad. At RH < 40%, transfer from all surfaces was <10%. Transfer efficiency increased markedly as RH increased, reaching a maximum of approximately 50%. The quantity of material transferred at specific RHs above 40% was also dependent on roughness of the surface material and the properties of the aerosol-deposited material. Smooth surfaces, such as melamine and stainless steel, generated higher transfer efficiencies compared to those with textured roughness, such as ABS pinseal and KYDEX® plastics. Pooled human saliva was transferred at a lower rate compared to artificial saliva, indicating the role of rheological properties. The artificial saliva data were modeled by non-linear regression and the impact of environmental humidity and temperature were evaluated within a Quantitative Microbial Risk Assessment model using SARS-CoV-2 as an example. This illustrated that the trade-off between transfer efficiency and virus survival may lead to the highest risks of fomite transmissions in indoor environments with higher humidity. Full article
(This article belongs to the Special Issue Aerosol Transmission of Viral Disease)
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12 pages, 1406 KiB  
Article
Comparison of Aerosol Stability of Different Variants of Ebola Virus and Marburg Virus and Virulence of Aerosolised Ebola Virus in an Immune-Deficient Mouse
by Sophie J. Smither, Lin S. Eastaugh and Mark S. Lever
Viruses 2022, 14(4), 780; https://doi.org/10.3390/v14040780 - 9 Apr 2022
Cited by 2 | Viewed by 1949
Abstract
During outbreaks of virus diseases, many variants may appear, some of which may be of concern. Stability in an aerosol of several Ebola virus and Marburg virus variants was investigated. Studies were performed measuring aerosol survival using the Goldberg drum but no significant [...] Read more.
During outbreaks of virus diseases, many variants may appear, some of which may be of concern. Stability in an aerosol of several Ebola virus and Marburg virus variants was investigated. Studies were performed measuring aerosol survival using the Goldberg drum but no significant difference in biological decay rates between variants was observed. In addition, historic data on virulence in a murine model of different Ebola virus variants were compared to newly presented data for Ebola virus Kikwit in the A129 Interferon alpha/beta receptor-deficient mouse model. Ebola virus Kikwit was less virulent than Ebola virus Ecran in our mouse model. The mouse model may be a useful tool for studying differences in virulence associated with different variants whereas aerosol stability studies may not need to be conducted beyond the species level. Full article
(This article belongs to the Special Issue Aerosol Transmission of Viral Disease)
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12 pages, 3257 KiB  
Article
A Miniaturized Electrostatic Precipitator Respirator Effectively Removes Ambient SARS-CoV-2 Bioaerosols
by Rachel K. Redmann, Brandon J. Beddingfield, Skye Spencer, Nicole R. Chirichella, Julian L. Henley, Wes Hager and Chad J. Roy
Viruses 2022, 14(4), 765; https://doi.org/10.3390/v14040765 - 6 Apr 2022
Cited by 4 | Viewed by 2545
Abstract
The inhalation of ambient SARS-CoV-2-containing bioaerosols leads to infection and pandemic airborne transmission in susceptible populations. Filter-based respirators effectively reduce exposure but complicate normal respiration through breathing zone pressure differentials; therefore, they are impractical for long-term use. Objectives: We tested the comparative effectiveness [...] Read more.
The inhalation of ambient SARS-CoV-2-containing bioaerosols leads to infection and pandemic airborne transmission in susceptible populations. Filter-based respirators effectively reduce exposure but complicate normal respiration through breathing zone pressure differentials; therefore, they are impractical for long-term use. Objectives: We tested the comparative effectiveness of a prototyped miniaturized electrostatic precipitator (mEP) on a filter-based respirator (N95) via the removal of viral bioaerosols from a simulated, inspired air stream. Methods: Each respirator was tested within a 16 L environmental chamber housed within a Class III biological safety cabinet within biosafety level 3 containment. SARS-CoV-2-containing bioaerosols were generated in the chamber, drawn by a vacuum through each respirator, and physical particle removal and viral genomic RNA were measured distal to the breathing zone of each device. Measurements and Main Results: The mEP respirator removed particles (96.5 ± 0.4%), approximating efficiencies of the N95 (96.9 ± 0.6%). The mEP respirator similarly decreased SARS-CoV-2 viral RNA (99.792%) when compared to N95 removal (99.942%), as a function of particle removal from the airstream distal to the breathing zone of each respirator. Conclusions: The mEP respirator approximated the performance of a filter-based N95 respirator for particle removal and viral RNA as a constituent of the SARS-CoV-2 bioaerosols generated for this evaluation. In practice, the mEP respirator could provide equivalent protection from ambient infectious bioaerosols as the N95 respirator without undue pressure drop to the wearer, thereby facilitating its long-term use in an unobstructed breathing configuration. Full article
(This article belongs to the Special Issue Aerosol Transmission of Viral Disease)
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12 pages, 1331 KiB  
Article
Inactivation Rates for Airborne Human Coronavirus by Low Doses of 222 nm Far-UVC Radiation
by David Welch, Manuela Buonanno, Andrew G. Buchan, Liang Yang, Kirk D. Atkinson, Igor Shuryak and David J. Brenner
Viruses 2022, 14(4), 684; https://doi.org/10.3390/v14040684 - 25 Mar 2022
Cited by 13 | Viewed by 5227
Abstract
Recent research using UV radiation with wavelengths in the 200–235 nm range, often referred to as far-UVC, suggests that the minimal health hazard associated with these wavelengths will allow direct use of far-UVC radiation within occupied indoor spaces to provide continuous disinfection. Earlier [...] Read more.
Recent research using UV radiation with wavelengths in the 200–235 nm range, often referred to as far-UVC, suggests that the minimal health hazard associated with these wavelengths will allow direct use of far-UVC radiation within occupied indoor spaces to provide continuous disinfection. Earlier experimental studies estimated the susceptibility of airborne human coronavirus OC43 exposed to 222-nm radiation based on fitting an exponential dose–response curve to the data. The current study extends the results to a wider range of doses of 222 nm far-UVC radiation and uses a computational model coupling radiation transport and computational fluid dynamics to improve dosimetry estimates. The new results suggest that the inactivation of human coronavirus OC43 within our exposure system is better described using a bi-exponential dose–response relation, and the estimated susceptibility constant at low doses—the relevant parameter for realistic low dose rate exposures—was 12.4 ± 0.4 cm2/mJ, which described the behavior of 99.7% ± 0.05% of the virus population. This new estimate is more than double the earlier susceptibility constant estimates that were based on a single-exponential dose response. These new results offer further evidence as to the efficacy of far-UVC to inactivate airborne pathogens. Full article
(This article belongs to the Special Issue Aerosol Transmission of Viral Disease)
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12 pages, 1013 KiB  
Article
Characterisation of Particle Size and Viability of SARS-CoV-2 Aerosols from a Range of Nebuliser Types Using a Novel Sampling Technique
by Susan Paton, Simon Clark, Antony Spencer, Isobel Garratt, Ikshitaa Dinesh, Katy-Anne Thompson, Allan Bennett and Thomas Pottage
Viruses 2022, 14(3), 639; https://doi.org/10.3390/v14030639 - 19 Mar 2022
Cited by 7 | Viewed by 2800
Abstract
Little is understood about the impact of nebulisation on the viability of SARS-CoV-2. In this study, a range of nebulisers with differing methods of aerosol generation were evaluated to determine SARS-CoV-2 viability following aerosolization. The aerosol particle size distribution was assessed using an [...] Read more.
Little is understood about the impact of nebulisation on the viability of SARS-CoV-2. In this study, a range of nebulisers with differing methods of aerosol generation were evaluated to determine SARS-CoV-2 viability following aerosolization. The aerosol particle size distribution was assessed using an aerosol particle sizer (APS) and SARS-CoV-2 viability was determined after collection into liquid media using All-Glass Impingers (AGI). Viable particles of SARS-CoV-2 were further characterised using the Collison 6-jet nebuliser in conjunction with novel sample techniques in an Andersen size-fractioning sampler to predict lung deposition profiles. Results demonstrate that all the tested nebulisers can generate stable, polydisperse aerosols (Geometric standard deviation (GSD) circa 1.8) in the respirable range (1.2 to 2.2 µm). Viable fractions (VF, units PFU/particle, the virus viability as a function of total particles produced) were circa 5 × 10−3. VF and spray factors were not significantly affected by relative humidity, within this system where aerosols were in the spray tube an extremely short time. The novel Andersen sample collection methods successfully captured viable virus particles across all sizes; with most particle sizes below 3.3 µm. Particle sizes, in MMAD (Mass Median Aerodynamic Diameters), were calculated from linear regression of log10-log10 transformed cumulative PFU data, and calculated MMADs accorded well with APS measurements and did not differ across collection method types. These data will be vital in informing animal aerosol challenge models, and infection prevention and control policies. Full article
(This article belongs to the Special Issue Aerosol Transmission of Viral Disease)
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20 pages, 50214 KiB  
Article
Environmental Effects on Viable Virus Transport and Resuspension in Ventilation Airflow
by Tatiana A. Baig, Meiyi Zhang, Brooke L. Smith and Maria D. King
Viruses 2022, 14(3), 616; https://doi.org/10.3390/v14030616 - 16 Mar 2022
Cited by 1 | Viewed by 2772
Abstract
To understand how SARS-CoV-2 spreads indoors, in this study bovine coronavirus was aerosolized as simulant into a plexiglass chamber with coupons of metal, wood and plastic surfaces. After aerosolization, chamber and coupon surfaces were swiped to quantify the virus concentrations using quantitative polymerase [...] Read more.
To understand how SARS-CoV-2 spreads indoors, in this study bovine coronavirus was aerosolized as simulant into a plexiglass chamber with coupons of metal, wood and plastic surfaces. After aerosolization, chamber and coupon surfaces were swiped to quantify the virus concentrations using quantitative polymerase chain reaction (qPCR). Bio-layer interferometry showed stronger virus association on plastic and metal surfaces, however, higher dissociation from wood in 80% relative humidity. Virus aerosols were collected with the 100 L/min wetted wall cyclone and the 50 L/min MD8 air sampler and quantitated by qPCR. To monitor the effect of the ventilation on the virus movement, PRD1 bacteriophages as virus simulants were disseminated in a ¾ scale air-conditioned hospital test room with twelve PM2.5 samplers at 15 L/min. Higher virus concentrations were detected above the patient’s head and near the foot of the bed with the air inlet on the ceiling above, exhaust bottom left on the wall. Based on room layout, air measurements and bioaerosol collections computational flow models were created to visualize the movement of the virus in the room airflow. The addition of air curtain at the door minimized virus concentration while having the inlet and exhaust on the ceiling decreased overall aerosol concentration. Controlled laboratory experiments were conducted in a plexiglass chamber to gain more insight into the fundamental behavior of aerosolized SARS-CoV-2 and understand its fate and transport in the ambient environment of the hospital room. Full article
(This article belongs to the Special Issue Aerosol Transmission of Viral Disease)
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20 pages, 2912 KiB  
Article
Efficacy of Ventilation, HEPA Air Cleaners, Universal Masking, and Physical Distancing for Reducing Exposure to Simulated Exhaled Aerosols in a Meeting Room
by Jayme P. Coyle, Raymond C. Derk, William G. Lindsley, Francoise M. Blachere, Theresa Boots, Angela R. Lemons, Stephen B. Martin, Jr., Kenneth R. Mead, Steven A. Fotta, Jeffrey S. Reynolds, Walter G. McKinney, Erik W. Sinsel, Donald H. Beezhold and John D. Noti
Viruses 2021, 13(12), 2536; https://doi.org/10.3390/v13122536 - 17 Dec 2021
Cited by 19 | Viewed by 6562
Abstract
There is strong evidence associating the indoor environment with transmission of SARS-CoV-2, the virus that causes COVID-19. SARS-CoV-2 can spread by exposure to droplets and very fine aerosol particles from respiratory fluids that are released by infected persons. Layered mitigation strategies, including but [...] Read more.
There is strong evidence associating the indoor environment with transmission of SARS-CoV-2, the virus that causes COVID-19. SARS-CoV-2 can spread by exposure to droplets and very fine aerosol particles from respiratory fluids that are released by infected persons. Layered mitigation strategies, including but not limited to maintaining physical distancing, adequate ventilation, universal masking, avoiding overcrowding, and vaccination, have shown to be effective in reducing the spread of SARS-CoV-2 within the indoor environment. Here, we examine the effect of mitigation strategies on reducing the risk of exposure to simulated respiratory aerosol particles within a classroom-style meeting room. To quantify exposure of uninfected individuals (Recipients), surrogate respiratory aerosol particles were generated by a breathing simulator with a headform (Source) that mimicked breath exhalations. Recipients, represented by three breathing simulators with manikin headforms, were placed in a meeting room and affixed with optical particle counters to measure 0.3–3 µm aerosol particles. Universal masking of all breathing simulators with a 3-ply cotton mask reduced aerosol exposure by 50% or more compared to scenarios with simulators unmasked. While evaluating the effect of Source placement, Recipients had the highest exposure at 0.9 m in a face-to-face orientation. Ventilation reduced exposure by approximately 5% per unit increase in air change per hour (ACH), irrespective of whether increases in ACH were by the HVAC system or portable HEPA air cleaners. The results demonstrate that mitigation strategies, such as universal masking and increasing ventilation, reduce personal exposure to respiratory aerosols within a meeting room. While universal masking remains a key component of a layered mitigation strategy of exposure reduction, increasing ventilation via system HVAC or portable HEPA air cleaners further reduces exposure. Full article
(This article belongs to the Special Issue Aerosol Transmission of Viral Disease)
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9 pages, 511 KiB  
Article
Sampling for SARS-CoV-2 Aerosols in Hospital Patient Rooms
by Morgan A. Lane, Maria Walawender, Andrew S. Webster, Erik A. Brownsword, Jessica M. Ingersoll, Candace Miller, Jesse Waggoner, Timothy M. Uyeki, William G. Lindsley and Colleen S. Kraft
Viruses 2021, 13(12), 2347; https://doi.org/10.3390/v13122347 - 23 Nov 2021
Cited by 5 | Viewed by 2215
Abstract
Evidence varies as to how far aerosols spread from individuals infected with SARS-CoV-2 in hospital rooms. We investigated the presence of aerosols containing SARS-CoV-2 inside of dedicated COVID-19 patient rooms. Three National Institute for Occupational Safety and Health BC 251 two-stage cyclone samplers [...] Read more.
Evidence varies as to how far aerosols spread from individuals infected with SARS-CoV-2 in hospital rooms. We investigated the presence of aerosols containing SARS-CoV-2 inside of dedicated COVID-19 patient rooms. Three National Institute for Occupational Safety and Health BC 251 two-stage cyclone samplers were set up in each patient room for a six-hour sampling period. Samplers were place on tripods, which each held two samplers at various heights above the floor. Extracted samples underwent reverse transcription polymerase chain reaction for selected gene regions of the SARS-CoV-2 virus nucleocapsid. Patient medical data were compared between participants in rooms where virus-containing aerosols were detected and those where they were not. Of 576 aerosols samples collected from 19 different rooms across 32 participants, 3% (19) were positive for SARS-CoV-2, the majority from near the head and foot of the bed. Seven of the positive samples were collected inside a single patient room. No significant differences in participant clinical characteristics were found between patients in rooms with positive and negative aerosol samples. SARS-CoV-2 viral aerosols were detected from the patient rooms of nine participants (28%). These findings provide reassurance that personal protective equipment that was recommended for this virus is appropriate given its spread in hospital rooms. Full article
(This article belongs to the Special Issue Aerosol Transmission of Viral Disease)
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Review

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14 pages, 699 KiB  
Review
Airborne Transmission of Foot-and-Mouth Disease Virus: A Review of Past and Present Perspectives
by Emma Brown, Noel Nelson, Simon Gubbins and Claire Colenutt
Viruses 2022, 14(5), 1009; https://doi.org/10.3390/v14051009 - 9 May 2022
Cited by 14 | Viewed by 6055
Abstract
The primary transmission route for foot-and-mouth disease (FMD), a contagious viral disease of cloven-hoofed animals, is by direct contact with infected animals. Yet indirect methods of transmission, such as via the airborne route, have been shown to play an important role in the [...] Read more.
The primary transmission route for foot-and-mouth disease (FMD), a contagious viral disease of cloven-hoofed animals, is by direct contact with infected animals. Yet indirect methods of transmission, such as via the airborne route, have been shown to play an important role in the spread of the disease. Airborne transmission of FMD is referred to as a low probability- high consequence event as a specific set of factors need to coincide to facilitate airborne spread. When conditions are favourable, airborne virus may spread rapidly and cause disease beyond the imposed quarantine zones, thus complicating control measures. Therefore, it is important to understand the nature of foot-and-mouth disease virus (FMDV) within aerosols; how aerosols are generated, viral load, how far aerosols could travel and survive under different conditions. Various studies have investigated emissions from infected animals under laboratory conditions, while others have incorporated experimental data in mathematical models to predict and trace outbreaks of FMD. However, much of the existing literature focussing on FMDV in aerosols describe work which was undertaken over 40 years ago. The aim of this review is to revisit existing knowledge and investigate how modern instrumentation and modelling approaches can improve our understanding of airborne transmission of FMD. Full article
(This article belongs to the Special Issue Aerosol Transmission of Viral Disease)
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