A dynamical overview of droplets in the transmission of respiratory infectious diseases

Zhou, Maoying; Zou, Jun

doi:10.1063/5.0039487

Cited by 38 publications

(22 citation statements)

References 379 publications

(238 reference statements)

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“…Such flows are relevant to mouth breathing and many spoken syllables. However, buoyancy effects, thermal currents near the human body, inhalation and exhalation flow due to nose breathing (Zhou & Zou 2021) and certain syllables, e.g. those affected by the position of the tongue, will generate flows in other directions and are subjects of future research.…”

Section: Discussionmentioning

confidence: 99%

Colliding respiratory jets as a mechanism of air exchange and pathogen transport during conversations

et al. 2021

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Air exchange between people has emerged in the COVID-19 pandemic as the important vector for transmission of the SARS-CoV-2 virus. We study the airflow and exchange between two unmasked individuals conversing face-to-face at short range, which can potentially transfer a high dose of a pathogen, because the dilution is small when compared to long-range airborne transmission. We conduct flow visualization experiments and direct numerical simulations of colliding respiratory jets mimicking the initial phase of a conversation. The evolution and dynamics of the jets are affected by the vertical offset between the mouths of the speakers. At low offsets the head-on collision of jets results in a `blocking effect', temporarily shielding the susceptible speaker from the pathogen carrying jet, although, the lateral spread of the jets is enhanced. Sufficiently large offsets prevent the interaction of the jets. At intermediate offsets (8-10 cm for 1 m separation), jet entrainment and the inhaled breath assist the transport of the pathogen-loaded saliva droplets towards the susceptible speaker's mouth. Air exchange is expected, in spite of the blocking effect arising from the interaction of the respiratory jets from the two speakers.

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Section: Discussionmentioning

confidence: 99%

Colliding respiratory jets as a mechanism of air exchange and pathogen transport during conversations

et al. 2021

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“…Person-to-person transmission of CoVID-19 mainly proceeds by direct contact or transmission of droplets with diameters ≥5 μm and smaller aerosol particles with diameters ≤5 μm [ 1 ] within a range of 0.001–500 μm [ 2 , 3 ]. Whereas virus-laden droplets are only received when a person is in close proximity to the emitter, aerosol particles remain hovering in the air and convectively spread in the environment distributing within large regions and rooms.…”

Section: Introductionmentioning

confidence: 99%

Effects of surgical masks on aerosol dispersion in professional singing

Kniesburges

Schlegel

Peters

et al. 2021

J Expo Sci Environ Epidemiol

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Background In the CoVID-19 pandemic, singing came into focus as a high-risk activity for the infection with airborne viruses and was therefore forbidden by many governmental administrations. Objective The aim of this study is to investigate the effectiveness of surgical masks regarding the spatial and temporal dispersion of aerosol and droplets during professional singing. Methods Ten professional singers performed a passage of the Ludwig van Beethoven’s “Ode of Joy” in two experimental setups—each with and without surgical masks. First, they sang with previously inhaled vapor of e-cigarettes. The emitted cloud was recorded by three cameras to measure its dispersion dynamics. Secondly, the naturally expelled larger droplets were illuminated by a laser light sheet and recorded by a high-speed camera. Results The exhaled vapor aerosols were decelerated and deflected by the mask and stayed in the singer’s near-field around and above their heads. In contrast, without mask, the aerosols spread widely reaching distances up to 1.3 m. The larger droplets were reduced by up to 86% with a surgical mask worn. Significance The study shows that surgical masks display an effective tool to reduce the range of aerosol dispersion during singing. In combination with an appropriate aeration strategy for aerosol removal, choir singers could be positioned in a more compact assembly without contaminating neighboring singers all singers.

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“…The number of particles exuded by coughing or sneezing varies considerably. 32–34 In this study, 3500 particles per cough and 11 700 particles per sneeze are ejected. Breath is a periodic behavior that exhales around 1600 particles every respiratory cycle.…”

Section: Methodsmentioning

confidence: 93%

Computational study on the transmission of the SARS-CoV-2 virus through aerosol in an elevator cabin: Effect of the ventilation system

2021

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Aerosol transmission is now well-established as a route in the spread of the SARS-CoV-2 virus. Factors influencing the transport of virus-laden particles in an elevator cabin are investigated computationally and include human respiratory events, locations of the infected person(s), and the ventilation system (ventilation mode, ventilation capacity, and vent schemes). “Breath,” “cough,” and “sneeze” are defined quantitatively by the fluid jet velocities and particle sizes. For natural ventilation, most particles exhaled by sneezing and coughing tend to deposit on surfaces quickly, but aerosol generated by breathing will remain suspended in the air longer. For forced ventilation, motions of particles under different ventilation capacities are compared. Larger particles otherwise deposited readily on solid surfaces may be slowed down by airflow. Air currents also accelerate the motions of smaller particles, facilitating the subsequent deposition of micrometer or sub-micrometer particles. Locations of the infected person(s) lead to different spreading scenarios due to the distinctive motions of the particles generated by the various respiratory events. Sneeze particles will likely contaminate the person in front of the infected passenger only. Cough particles will increase the risk of all the people around the injector. Breath particles tend to spread throughout the confined environment. An optimized vent scheme is introduced and can reduce particles suspended in the air by up to 80% as compared with commonly used schemes. The purification function of this vent model is robust to various positions of the infected passenger.

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A dynamical overview of droplets in the transmission of respiratory infectious diseases

Cited by 38 publications

References 379 publications

Colliding respiratory jets as a mechanism of air exchange and pathogen transport during conversations

Colliding respiratory jets as a mechanism of air exchange and pathogen transport during conversations

Effects of surgical masks on aerosol dispersion in professional singing

Computational study on the transmission of the SARS-CoV-2 virus through aerosol in an elevator cabin: Effect of the ventilation system

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