Airborne dispersion of droplets during coughing: a physical model of viral transmission

Li, Hongying; Leong, Fong Yew; Xu, George; Kang, Chang Wei; Lim, Keng Hui; Tan, Ban Hock; Loo, Chian Min

doi:10.1038/s41598-021-84245-2

Cited by 46 publications

(36 citation statements)

References 65 publications

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“…3 shows the specific setup of barrier heights and locations. In addition, it was assumed that an infected person considered as source of COVID, who produced droplets or aerosols containing viruses (with a coughing speed of 13m/s downwards at 27.5°) (Kwon et al 2012, Li et al 2021. Three typical positions for pollution source (infected person) of A, B and C are selected representing alternative horizontal distances between personnel and air diffusers, as demonstrated in Fig.…”

Section: Methodsmentioning

confidence: 99%

“…The parameters of pollutant source location and barrier height are further explored in simulation cases 5-19 under modified ventilation mode. A single pollutant source is considered, assuming an infected personnel with continuous coughing that produces viruses (with an airflow velocity of 13m/s at the mouth downwards at 27.5°)(Kwon et al 2012, Li et al 2021) considering an airflow temperature of mouth as 36 o C (breathing rate for remaining personnel is assumed negligible). In each simulation case, the single pollutant source is placed in positions A, B or C, and the source intensity is set as 1E-04 (quantum/m 3 ).…”

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confidence: 99%

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Mitigating COVID-19 infection disease transmission in indoor environment using physical barriers

Ren

Wang

et al. 2021

Sustainable Cities and Society

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During the normalized phase of COVID-19, droplets or aerosol particles produced by infected personnel are considered as the potential source of infection with uncertain exposure risk. As such, in densely populated open spaces, it is necessary to adopt strategies to mitigate the risk of infection disease transmission while providing sufficient ventilation air. An example of such strategies is use of physical barriers. In this study, the impact of barrier heights on the spread of aerosol particles is investigated in an open office environment with the well-designed ventilation mode and supply air rate. The risk of infection disease transmission is evaluated using simulation of particle concentration in different locations and subject to a number of source scenarios. It was found that a barrier height of at least 60cm above the desk surface is needed to effectively prevent the transmission of viruses. For workstations within 4m from the outlet, a 70cm height is considered, and with a proper ventilation mode, it is shown that the barriers can reduce the risk of infection by 72%. However, for the workstations further away from the outlet (beyond 4m), the effect of physical barrier cannot be that significant. In summary, this study provides a theoretical analysis for implementing physical barriers, as a low-cost mitigation strategy, subject to various height scenarios and investigation of their effectiveness in reducing the infection transmission probability.

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Mitigating COVID-19 infection disease transmission in indoor environment using physical barriers

Ren

Wang

et al. 2021

Sustainable Cities and Society

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“…it restricts the height of both the swabber and patients” Could not swab sitting/wheelchair patients [ 6 ] “it is not wheelchair or elderly friendly.” Cubicle too small or short [ 2 ] “however, the top of the booth is too low for Caucasian patients” “For a ladies [ sic ] frame it’s a good fit but not for the larger built guys” Dimensions [ 19 ] Too bulky/wanted foldable [ 10 ] “Try to design a foldable one.” “no need to be so bulky and tall” Patient cubicle dimensions [ 3 ] “Too far for patient. Patient can move away during swab.” Too heavy [ 3 ] “heavy to push in and out of the clinic after every session” Miscellaneous [ 19 ] Want it more enclosed [ 6 ] “There is no “door” to total close patient in so to ensure the aerosol particles are contain within the booth…” Enhance places to put things [ 5 ] “Put a ledge on patients’ side so the things less likely to drop” “compartments to put disinfectants and swabbing materal [ sic ]” Others [ 8 ] – 2 or fewer comments per theme “Difficult for patient to hear me while swabbing - I bought a mic and speaker set to overcome this” …”

Section: Resultsmentioning

confidence: 99%

“…However, it is reasonable to assume that the transmission risk to swabber is high, as during swabbing the potentially infectious patient stands less than a metre away, his face is exposed, and he may cough. These three factors multiply the risk to many times that of a typical interaction with masks worn, more than a metre apart and without coughing [ 7 , 8 ]. Furthermore, as SARS-CoV-2 transmission is via droplets, aerosols and fomites, and transmission risk is greater in confined spaces [ 9 ], there may be risks to other users of the space, raising the issue of disinfection.…”

Section: Introductionmentioning

confidence: 99%

A mobile swabbing booth to address Singapore GPs’ concerns about swabber protection: human-centred design during the COVID-19 pandemic

Teo

Khoo

et al. 2021

BMC Fam Pract

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Background During the COVID-19 pandemic, the Ministry of Health asked Singapore’s private general practitioners (GPs) to perform swab testing in their clinics, but some GPs had concerns about swabber protection. Our aim was to develop a swabbing booth to address these concerns. Methods We developed a prototype with potential GP users using a human-centred design approach and piloted it with 10 GP clinics. The pilot was then extended to 170 GP clinics around Singapore. These GPs were then surveyed on user satisfaction. Results Ninety-three GPs (54%) responded. The majority (75%) practiced in public residential estates in small practices (mean 1.95 doctors). 86% requested the booth to enhance swabber protection. 74% “would recommend” or “would strongly recommend” the booth to colleagues. 79% continue to use the booth to conduct swab tests. 92% liked that it offered swabber protection. 71% liked that the booth created a separate space for swabbing and 64% liked its ease of disinfection. 47% started swabbing only after receiving the booth and 58% said the booth was “important” or “very important” to their decision to participate in swab testing. However, 34% disliked that it took up too much space and the most frequently critiqued area was the gloves. Conclusion The human-centred design approach generated a product that had high user satisfaction, addressed GPs’ concerns of swabber protection and increased GPs’ participation in swab testing. The booth may be useful where GPs are concerned about swabber protection and space is limited.

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“…Respiratory infections can be transmitted through droplets (> 5µm) and droplet nuclei (< 5µm) [1][2][3] . According to the World Health Organization (WHO) report 2 COVID-19 in particular, is primarily transmitted through droplets and contact [4][5][6] .…”

Section: Introductionmentioning

confidence: 99%

Droplet Nuclei Caustic Formations In Exhaled Vortex Rings

Papoutsakis

Gavaises

2021

Preprint

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Vortex ring structures occur in light or hoarse cough configurations. These instances consist of short impulses of exhaled air resulting to a self-contained structure that can travel large distances. The present study is the first implementation of the second order Fully Lagrangian Approach (FLA) for three-dimensional realistic flow-fields obtained by means of Computational Fluid Dynamics (CFD) and provides a method to calculate the occurrence and the intensity of caustic formations. The carrier phase flow field is resolved by means of second order accurate Direct Numerical Simulation (DNS) based on a Finite Difference approach for the momentum equations, while a spectral approach is followed for the Poisson equation using Fast Fourier Transform (FFT). The effect of the undulations of the carrier phase velocity due to large scale vortical structures and turbulence is investigated. The evaluation of the higher order derivatives needed by the second order FLA is achieved by prefabricated least squares second order interpolations in the three dimensions. The method allows for the simulation of the clustering of droplets and droplet nuclei exhaled in ambient air in conditions akin to light cough. Given the ambiguous conditions of vortex-ring formation during cough instances, three different formation numbers n = UT /D are assumed, i.e. underdeveloped (n = 2), ideal (n = 3.7) and over-developed VRs (n = 6). The formation of clusters results in the spatial variance of the airborne viral load. This un-mixing of exhumed aerosols is related to the formation of localised high viral load distributions that can be linked to super-spreading events.

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Airborne dispersion of droplets during coughing: a physical model of viral transmission

Cited by 46 publications

References 65 publications

Mitigating COVID-19 infection disease transmission in indoor environment using physical barriers

Mitigating COVID-19 infection disease transmission in indoor environment using physical barriers

A mobile swabbing booth to address Singapore GPs’ concerns about swabber protection: human-centred design during the COVID-19 pandemic

Droplet Nuclei Caustic Formations In Exhaled Vortex Rings

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