Predominance of inhalation route in short-range transmission of respiratory viruses: Investigation based on computational fluid dynamics
)
Download citation
289
Views
15
Downloads
4
Crossref
5
WoS
3
Scopus
0
CSCD
During the coronavirus disease 2019 pandemic, short-range virus transmission has been observed to have a higher risk of causing infection than long-range virus transmission. However, the roles played by the inhalation and large droplet routes cannot be distinguished in practice. A recent analytical study revealed the predominance of short-range inhalation over the large droplet spray route as causes of respiratory infections. In the current study, short-range exposure was analyzed via computational fluid dynamics (CFD) simulations using a discrete phase model. Detailed facial membranes, including eyes, nostrils, and a mouth, were considered. In CFD simulations, there is no need for a spherical approximation of the human head for estimating deposition nor the "anisokinetic aerosol sampling" approximation for estimating inhalation in the analytical model. We considered two scenarios (with two spheres [Scenario 1] and two human manikins [Scenario 2]), source–target distances of 0.2 to 2 m, and droplet diameters of 3 to 1,500 μm. The overall CFD exposure results agree well with data previously obtained from a simple analytical model. The CFD results confirm the predominance of the short-range inhalation route beyond 0.2 m for expiratory droplets smaller than 50 μm during talking and coughing. A critical droplet size of 87.5 μm was found to differentiate droplet behaviors. The number of droplets deposited on the target head exceeded those exposed to facial membranes, which implies a risk of exposure through the immediate surface route over a short range.
menu
Predominance of inhalation route in short-range transmission of respiratory viruses: Investigation based on computational fluid dynamics
)
Abstract
During the coronavirus disease 2019 pandemic, short-range virus transmission has been observed to have a higher risk of causing infection than long-range virus transmission. However, the roles played by the inhalation and large droplet routes cannot be distinguished in practice. A recent analytical study revealed the predominance of short-range inhalation over the large droplet spray route as causes of respiratory infections. In the current study, short-range exposure was analyzed via computational fluid dynamics (CFD) simulations using a discrete phase model. Detailed facial membranes, including eyes, nostrils, and a mouth, were considered. In CFD simulations, there is no need for a spherical approximation of the human head for estimating deposition nor the "anisokinetic aerosol sampling" approximation for estimating inhalation in the analytical model. We considered two scenarios (with two spheres [Scenario 1] and two human manikins [Scenario 2]), source–target distances of 0.2 to 2 m, and droplet diameters of 3 to 1,500 μm. The overall CFD exposure results agree well with data previously obtained from a simple analytical model. The CFD results confirm the predominance of the short-range inhalation route beyond 0.2 m for expiratory droplets smaller than 50 μm during talking and coughing. A critical droplet size of 87.5 μm was found to differentiate droplet behaviors. The number of droplets deposited on the target head exceeded those exposed to facial membranes, which implies a risk of exposure through the immediate surface route over a short range.
References(47)
Abkarian M, Mendez S, Xue N, et al. (2020). Speech can produce jet-like transport relevant to asymptomatic spreading of virus. Proceedings of the National Academy of Sciences of the United States of America, 117: 25237–25245.
Banik RK, Ulrich A (2020). Evidence of short-range aerosol transmission of SARS-CoV-2 and call for universal airborne precautions for anesthesiologists during the COVID-19 pandemic. Anesthesia and Analgesia, 131: e102–e104.
Behera S, Bhardwaj R, Agrawal A (2021). Effect of co-flow on fluid dynamics of a cough jet with implications in spread of COVID-19. Physics of Fluids, 33: 101701.
Chao CYH, Wan MP, Morawska L, et al. (2009). Characterization of expiration air jets and droplet size distributions immediately at the mouth opening. Journal of Aerosol Science, 40: 122–133.
Chen W, Zhang N, Wei J, et al. (2020). Short-range airborne route dominates exposure of respiratory infection during close contact. Building and Environment, 176: 106859.
Chen W, Qian H, Zhang N, et al. (2022). Extended short-range airborne transmission of respiratory infections. Journal of Hazardous Materials, 422: 126837.
Coroneo MT, Collignon PJ (2021). SARS-CoV-2: Eye protection might be the missing key. The Lancet Microbe, 2: e173–e174.
Craven BA, Settles GS (2006). A computational and experimental investigation of the human thermal plume. Journal of Fluids Engineering, 128: 1251–1258.
de Dear RJ, Arens E, Hui Z, et al. (1997). Convective and radiative heat transfer coefficients for individual human body segments. International Journal of Biometeorology, 40: 141–156.
Duguid JP (1946). The size and the duration of air-carriage of respiratory droplets and droplet-nuclei. Epidemiology & Infection, 44: 471–479.
Dunnett SJ, Ingham DB (1988). An empirical model for the aspiration efficiencies of blunt aerosol samplers orientated at an angle to the oncoming flow. Aerosol Science and Technology, 8: 245–264.
Gao NP, Niu JL (2005). CFD study of the thermal environment around a human body: a review. Indoor and Built Environment, 14: 5–16.
Jia W, Wei J, Cheng P, et al. (2022). Exposure and respiratory infection risk via the short-range airborne route. Building and Environment, 219: 109166.
Lei H, Xiao S, Cowling BJ, et al. (2020). Hand hygiene and surface cleaning should be paired for prevention of fomite transmission. Indoor Air, 30: 49–59.
Li Y, Leung GM, Tang JW, et al. (2007). Role of ventilation in airborne transmission of infectious agents in the built environment—A multidisciplinary systematic review. Indoor Air, 17: 2–18.
Li Y (2021). Basic routes of transmission of respiratory pathogens—A new proposal for transmission categorization based on respiratory spray, inhalation, and touch. Indoor Air, 31: 3–6.
Li Y, Qian H, Hang J, et al. (2021). Probable airborne transmission of SARS-CoV-2 in a poorly ventilated restaurant. Building and Environment, 196: 107788.
Li X, Ai Z, Ye J, et al. (2022a). Airborne transmission during short-term events: Direct route over indirect route. Building Simulation, 15: 2097–2110.
Li Y, Cheng P, Jia W (2022b). Poor ventilation worsens short-range airborne transmission of respiratory infection. Indoor Air, 32: e12946.
Lindsley WG, Blachere FM, Thewlis RE, et al. (2010). Measurements of airborne influenza virus in aerosol particles from human coughs. PLoS One, 5: e15100.
Liu L, Li Y, Nielsen PV, et al. (2017). Short-range airborne transmission of expiratory droplets between two people. Indoor Air, 27: 452–462.
Liu Z, Zhu H, Song Y, et al. (2022). Quantitative distribution of human exhaled particles in a ventilation room. Building Simulation, 15: 859–870.
Miller SL, Nazaroff WW, Jimenez JL, et al. (2021). Transmission of SARS-CoV-2 by inhalation of respiratory aerosol in the Skagit Valley Chorale superspreading event. Indoor Air, 31: 314–323.
Milton DK (2020). A Rosetta stone for understanding infectious drops and aerosols. Journal of the Pediatric Infectious Diseases Society, 9: 413–415.
Morawska L, Johnson GR, Ristovski ZD, et al. (2009). Size distribution and sites of origin of droplets expelled from the human respiratory tract during expiratory activities. Journal of Aerosol Science, 40: 256–269.
Morawska L, Tang JW, Bahnfleth W, et al. (2020). How can airborne transmission of COVID-19 indoors be minimised? Environment International, 142: 105832.
Mui KW, Wong LT, Wu CL, et al. (2009). Numerical modeling of exhaled droplet nuclei dispersion and mixing in indoor environments. Journal of Hazardous Materials, 167: 736–744.
Ou C, Hu S, Luo K, et al. (2022). Insufficient ventilation led to a probable long-range airborne transmission of SARS-CoV-2 on two buses. Building and Environment, 207: 108414.
Popov TA, Dunev S, Kralimarkova TZ, et al. (2007). Evaluation of a simple, potentially individual device for exhaled breath temperature measurement. Respiratory Medicine, 101: 2044–2050.
Prather KA, Marr LC, Schooley RT, et al. (2020). Airborne transmission of SARS-CoV-2. Science, 370: 303–304.
Somsen GA, van Rijn C, Kooij S, et al. (2020). Small droplet aerosols in poorly ventilated spaces and SARS-CoV-2 transmission. The Lancet Respiratory Medicine, 8: 658–659.
Sun W, Ji J (2007). Transport of droplets expelled by coughing in ventilated rooms. Indoor and Built Environment, 16: 493–504.
Wei J, Li Y (2015). Enhanced spread of expiratory droplets by turbulence in a cough jet. Building and Environment, 93: 86–96.
Wells WF (1934). On air-borne infection: study II. Droplets and droplet nuclei. American Journal of Epidemiology, 20: 611–618.
Xie X, Li Y, Chwang AY, et al. (2007). How far droplets can move in indoor environments—Revisiting the Wells evaporation-falling curve. Indoor Air, 17: 211–225.
Xu J, Psikuta A, Li J, et al. (2019). Influence of human body geometry, posture and the surrounding environment on body heat loss based on a validated numerical model. Building and Environment, 166: 106340.
Yakhot V, Orszag SA (1986). Renormalization group analysis of turbulence. I. Basic theory. Journal of Scientific Computing, 1: 3-51.
Zhang N, Chen W, Chan PT, et al. (2020a). Close contact behavior in indoor environment and transmission of respiratory infection. Indoor Air, 30: 645–661.
Zhang N, Jia W, Wang P, et al. (2020b). Most self-touches are with the nondominant hand. Scientific Reports, 10: 10457.
Zhang N, Chen X, Jia W, et al. (2021). Evidence for lack of transmission by close contact and surface touch in a restaurant outbreak of COVID-19. The Journal of Infection, 83: 207–216.
Zhao P, Li Y, Tsang TL, et al. (2018). Equilibrium of particle distribution on surfaces due to touch. Building and Environment, 143: 461–472.
Zhao P, Chan PT, Gao Y, et al. (2019). Physical factors that affect microbial transfer during surface touch. Building and Environment, 158: 28–38.
Zhu S, Kato S, Yang JH (2006). Study on transport characteristics of saliva droplets produced by coughing in a calm indoor environment. Building and Environment, 41: 1691–1702.
Publication history
Copyright
Acknowledgements
This work was supported by a General Research Fund (grant number 17202719) provided by the Research Grants Council of Hong Kong.
FEEDBACK 
TOP