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

Chong, Kai Leong; Ng, Chong Shen; Hori, Naoki; Yang, Rui; Verzicco, Roberto; Lohse, Detlef

doi:10.1103/physrevlett.126.034502

Cited by 158 publications

(220 citation statements)

References 64 publications

(81 reference statements)

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“…[25] and Chong et al . [21], we suggested a value d M = 50 µm. To look at it, we took the example case and re-calculated it for 23 equal log-width bins between 100 nm and 100 µm and considered the concentration densities and mean infection risks if the top 0, 2, and 4 bins were discarded, thereby setting decreasing d M to 100 µm, 54.8 µm, and 30.1 µm.…”

Section: Discussionmentioning

confidence: 99%

“…The simulations of Chong et al . [21] indicate that 100 µm aerosols are quite ballistic and quickly fall out of the exhaled plume, but 10 µm aerosols are carried along with the plume and stay in the air despite their evaporation being greatly slowed. This suggests that d M should be chosen somewhere in the 10–100 µm range, which is further supported by the Wells curves found by Xie et al .…”

Section: Fundamentalsmentioning

confidence: 99%

“…This includes breathing rates for different activities [14–17]; the dynamics of exhaled puffs and the particles within them by breathing, speech, coughing, etc. [18–21]; the generation and ejection of aerosols and larger droplets by breathing, speech, coughing, etc. [16, 19, 22, 23]; aerosol/droplet growth/evaporation in response to temperature and humidity [19, 24–28]; the dynamics of inertial particles in turbulence; mixing and transport [18–21, 29, 30]; ventilation and convection in indoor environments [30]; etc.…”

Section: Introductionmentioning

confidence: 99%

“…[18–21]; the generation and ejection of aerosols and larger droplets by breathing, speech, coughing, etc. [16, 19, 22, 23]; aerosol/droplet growth/evaporation in response to temperature and humidity [19, 24–28]; the dynamics of inertial particles in turbulence; mixing and transport [18–21, 29, 30]; ventilation and convection in indoor environments [30]; etc. There have been a number of recent papers that each go into several of these topics written during the course of the ongoing SARS-CoV-2 pandemic [19, 28–31], which while focused on SARS-CoV-2 are also applicable to other airborne diseases.…”

Section: Introductionmentioning

confidence: 99%

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Risk assessment for airborne disease transmission by poly-pathogen aerosols

Bodenschatz

Bagheri

2020

Preprint

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In 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.

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Section: Discussionmentioning

confidence: 99%

Section: Fundamentalsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Risk assessment for airborne disease transmission by poly-pathogen aerosols

Bodenschatz

Bagheri

2020

Preprint

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“…The same is true for surface deposits, particularly as it is not known why viral viability is enhanced in that form 16,25 . The drying of aerosols when emitted into ambient air has been quite extensively studied [27][28][29] and modelled 27,28,30,31 , often with the aim of predicting when droplets, initially large enough to sediment in still air, will shrink enough to remain suspended. In the biomedical literature, a droplet that has dried to equilibrium with the ambient air is called a droplet nucleus 1 .…”

Section: Introductionmentioning

confidence: 99%

Drying of virus-containing aerosol particles: Modelling effects of droplet origin and composition

Jarvis

2021

Preprint

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Virus-containing aerosol droplets emitted by breathing, speech or coughing dry rapidly to equilibrium with ambient relative humidity (RH), increasing in solute concentration with effects on virus survival and decreasing in diameter with effects on sedimentation and respiratory uptake. In simulations starting from drying data on mixed NaCl/KCl aerosols, the supersaturated salt concentrations were shown to reach 20-25M at the efflorescence RH of 40-55%, depending on the K:Na ratio. These salt concentrations may inactivate some viruses. The dependence on K:Na ratio implies that the evaporation curves differ between aerosols derived from saliva and from airway surfaces. Differences in drying behaviour are consequently predicted between breathing, speech and coughing emissions and between droplet size fractions within these. The direct effect of liquid droplet size through the Kelvin term was shown to be smaller and restricted to breath emissions. Comparative simulations starting from osmotic pressure measurements on airway surface liquid showed that salts are the primary determinants of drying equilibria down to the efflorescence RH, and macromolecules at lower RH.

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From Microscopic Droplets to Macroscopic Crowds: Crossing the Scales in Models of Short‐Range Respiratory Disease Transmission, with Application to COVID‐19

2023

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Short‐range exposure to airborne virus‐laden respiratory droplets is an effective transmission route of respiratory diseases, as exemplified by Coronavirus Disease 2019 (COVID‐19). In order to assess the risks associated with this pathway in daily‐life settings involving tens to hundreds of individuals, the chasm needs to be bridged between fluid dynamical simulations and population‐scale epidemiological models. This is achieved by simulating droplet trajectories at the microscale in numerous ambient flows, coarse‐graining their results into spatio‐temporal maps of viral concentration around the emitter, and coupling these maps to field‐data about pedestrian crowds in different scenarios (streets, train stations, markets, queues, and street cafés). At the individual scale, the results highlight the paramount importance of the velocity of the ambient air flow relative to the emitter's motion. This aerodynamic effect, which disperses infectious aerosols, prevails over all other environmental variables. At the crowd's scale, the method yields a ranking of the scenarios by the risks of new infections, dominated by the street cafés and then the outdoor market. While the effect of light winds on the qualitative ranking is fairly marginal, even the most modest air flows dramatically lower the quantitative rates of new infections.

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

Cited by 158 publications

References 64 publications

Risk assessment for airborne disease transmission by poly-pathogen aerosols

Risk assessment for airborne disease transmission by poly-pathogen aerosols

Drying of virus-containing aerosol particles: Modelling effects of droplet origin and composition

From Microscopic Droplets to Macroscopic Crowds: Crossing the Scales in Models of Short‐Range Respiratory Disease Transmission, with Application to COVID‐19

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