Breathing, speaking, coughing or sneezing: What drives transmission of SARS‐CoV‐2?

Journal of Internal Medicine, Journal Year: 2021, Volume and Issue: 290(5), P. 1010 - 1027

Published: June 8, 2021

Abstract The SARS‐CoV‐2 virus is highly contagious, as demonstrated by numerous well‐documented superspreading events. infection commonly starts in the upper respiratory tract (URT) but can migrate to lower (LRT) and other organs, often with severe consequences. Whereas LRT lead shedding of via breath cough droplets, URT enables abundant speech droplets. Their viral load be high carriers mild or no symptoms, an observation linked abundance SARS‐CoV‐2‐susceptible cells oral cavity epithelium. Expelled droplets rapidly lose water through evaporation, smaller ones transforming into long‐lived aerosol. Although largest carry more virions, they are few number, fall ground therefore play a relatively minor role transmission. Of concern small aerosol, which descend deep cause disease. However, since their total volume small, amount low. Nevertheless, closed environments inadequate ventilation, accumulate, elevates risk direct infection. most large fraction aerosol that intermediate‐sized because it remains suspended air for minutes transported over considerable distances convective currents. this speech‐generated combined its pre‐ asymptomatic individuals, strongly implicates airborne transmission primary contributor rapid spread.

Language: Английский

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The role of viscosity on drop impact forces on non-wetting surfaces

Journal of Fluid Mechanics, Journal Year: 2025, Volume and Issue: 1004

Published: Jan. 30, 2025

A liquid drop impacting a rigid substrate undergoes deformation and spreading due to normal reaction forces, which are counteracted by surface tension. On non-wetting substrate, the subsequently retracts takes off. Our recent work (Zhang et al. , Phys. Rev. Lett. vol. 129, 2022, 104501) revealed two peaks in temporal evolution of force $F(t)$ – one at impact another jump-off. The second peak coincides with Worthington jet formation, vanishes high viscosities increased viscous dissipation affecting flow focusing. In this article, using experiments, direct numerical simulations scaling arguments, we characterize both amplitude $F_1$ takeoff ( $F_2$ ) elucidate their dependency on control parameters: Weber number $We$ (dimensionless kinetic energy) Ohnesorge $Oh$ viscosity). first time $t_1$ reach it depend inertial scales for low viscosity liquids, remaining nearly constant up 100 times that water. For balance rate change energy obtain new laws: $F_1/F_\rho \sim \sqrt {Oh}$ $t_1/\tau _\rho 1/\sqrt where $F_\rho$ $\tau _\rho$ scales, respectively, consistent our data. $t_2$ appears is set inertiocapillary scale _\gamma$ independent velocity drop. However, these properties dictate magnitude amplitude.

Language: Английский

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A review on measurements of SARS-CoV-2 genetic material in air in outdoor and indoor environments: Implication for airborne transmission

The Science of The Total Environment, Journal Year: 2021, Volume and Issue: 809, P. 151137 - 151137

Published: Oct. 25, 2021

Language: Английский

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Aerosol generating procedures: are they of relevance for transmission of SARS-CoV-2?

The Lancet Respiratory Medicine, Journal Year: 2021, Volume and Issue: 9(7), P. 687 - 689

Published: May 7, 2021

It is now generally accepted that SARS-CoV-2 can be spread by aerosols as well larger droplets from the upper respiratory tract, although relative importance of aerosol transmission remains incompletely answered.1Pöhlker ML Krüger OO Förster J-D et al.Respiratory and in infectious diseases.arXiv. 2021; (published online 1 March.)http://arxiv.org/abs/2103.01188Google Scholar Despite this, current UK infection control guidance for hospitals centred on premise are only generated specific medical interventions designated generating procedures (AGPs).2WHOInfection prevention epidemic- pandemic-prone acute infections health care. World Health Organization, Geneva2014Google This draws epidemiological observations during 2003 outbreak severe syndrome, which certain appeared to associated with an increased risk staff (particularly tracheal intubation), these had a theoretical viral aerosolisation.3Tran K Cimon Severn M Pessoa-Silva CL Conly J Aerosol healthcare workers: systematic review.PLoS One. 2012; 7e35797Crossref PubMed Scopus (1322) Google However, evidence supporting aerosolisation was, before pandemic, remarkably slim, being assumed basis precautionary principle low quality mechanistic studies.4Jackson T Deibert D Wyatt G al.Classification aerosol-generating procedures: rapid review.BMJ Open Respir Res. 2020; 7e000730Crossref (118) view generation subsequently led dichotomisation—later codified international guidance2WHOInfection Scholar—that categorised all activities into either AGPs, where potentially generated, versus everything else, presumed negligible. The logical extension this dichotomy has resulted health-care workers many countries undertaking classified AGPs wearing higher levels personal protective equipment (PPE), such FFP3 or N95 masks, whereas those providing other care have not been afforded same protection, considered outside AGPs.5Public England6. COVID-19 guidance: procedures.https://www.gov.uk/government/publications/wuhan-novel-coronavirus-infection-prevention-and-control/covid-19-infection-prevention-and-control-guidance-aerosol-generating-proceduresDate: 2020Date accessed: April 1, 2021Google Although was reasonable at start recent sampling studies multiple groups investigating several currently defined revealed more information potential procedures. In fact, emissions intubation, high-flow nasal oxygen, non-invasive ventilation low, similar sampled concentrations tidal breathing speaking.6Wilson NM Marks GB Eckhardt A al.The effect activity, support facemasks its relevance COVID-19.Anaesthesia. March 30.)https://doi.org/10.1111/anae.15475Crossref (80) Scholar, 7Hamilton F Gregson Arnold al.Aerosol emission tract: analysis risks oxygen delivery systems.bioRxiv. Feb 1.)http://medrxiv.org/lookup/doi/10.1101/2021.01.29.21250552Google 8Brown FKA Shrimpton al.A quantitative evaluation intubation extubation.Anaesthesia. 76: 174-181Crossref (134) 9Alsved Matamis Bohlin R al.Exhaled particles singing talking.Aerosol Sci Technol. 54: 1245-1248Crossref (145) Critically, also confirm coughing both healthy volunteers, patients (with without COVID-19), generates orders magnitude than AGPs.6Wilson cough procedure sufficient AGP. Consequently, advises highest precaution PPE demonstrably high (compared coughing) lower grade droplet when (eg, caring confirmed prolonged period time poorly ventilated settings). we others sought quantify generation, it should clear simple observation does pathogen transmission; much exacting task quantifying airborne carried so far proven intractable. More research ongoing across range clinical settings. based date, patient likely generate AGPs. appears supported evidence, points ward (who acutely dyspnoeic, COVID-19) compared intensive staff—although noted interpretation data confounded mix, among factors.10Cook TM Lennane S Occupational anaesthesia staff—low-risk specialties high-risk setting.Anaesthesia. 295-330Crossref (21) We propose end term procedure, neither accurate (aerosol above procedures), implies (rather normal events), misidentifies source risk, applies binary definition situation complex. Instead, clinicians follow evidence-based framework accounts major drivers focus physical exposure suspected critical component (panel).PanelProposed factors included matrix SARS-CoV-2Patient (by largest factor)The probability having infection, since acquisition. Risk symptoms, PCR positivity, vaccination status. Note symptoms exertion generation.Duration exposureThe duration place. length required close proximity naturally increases transmission.Health-care practitioner COVID-19Age, sex, body mass index, comorbidities, status.Proximity riskExposure any intervention requiring contact risk. includes (such mouthcare) examination (especially relating tract throat swab, nasendoscopy, intubation)Environmental riskVentilation, humidity, temperature Patient factor) generation. Duration transmission. Health-care Age, Proximity Exposure intubation) Environmental Ventilation, Subsequently, additional known relevant transmission, ventilation, proximity, patients, assessing while recognising changing epidemiology setting. summary, increasingly via possible might represent significant route. emerging indicates unlikely play role poses staff. AGP face validity nor construct validity. plain sight: close, people suspected, have, poor. declare no competing interests. Download .pdf (.15 MB) Help pdf files Supplementary appendix

Language: Английский

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Sources, compositions, spatio-temporal distributions, and human health risks of bioaerosols: A review

Atmospheric Research, Journal Year: 2024, Volume and Issue: 305, P. 107453 - 107453

Published: April 30, 2024

Language: Английский

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Analytical challenges when sampling and characterising exhaled aerosol

Aerosol Science and Technology, Journal Year: 2021, Volume and Issue: 56(2), P. 160 - 175

Published: Oct. 25, 2021

Respiratory particles produced by breathing, coughing, and speaking or generated during medical procedures serve as important routes for disease transmission. Characterizing the number of well their size distribution is fundamental guiding policy on infection control. However, sampling such carries inherent challenges. are polydisperse in size, temporally spatially variable, emitted very low concentrations, usually lower than preexisting aerosol concentration indoor environments. In addition, they typically a highly dynamic, warm humid jet, leading to further rapid processes, dispersion evaporation. Here, we discuss considerations respiratory aerosol, focusing <20 μm diameter. Instruments capable counting single-particles within this range commercially available. We provide recommendations experimental protocols demonstrate limitations behind approaches. highlight importance measurement space with background possible, long possible enable accurate quantitation an plume. This particularly larger (>5 diameter) that so may require hours time be accurately quantified. explore relationship between flow rates exhalation instrument consequent quantification particle flux. also transport evaporation dynamics liquid jets, impacts conducting studies.

Language: Английский

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Electrospun bimodal nanofibrous membranes for high-performance, multifunctional, and light-weight air filtration: A review

Separation and Purification Technology, Journal Year: 2024, Volume and Issue: 358, P. 130417 - 130417

Published: Nov. 6, 2024

Language: Английский

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Effect of airflow rate on CO2 concentration in downflow indoor ventilation

Indoor Environments, Journal Year: 2024, Volume and Issue: 1(2), P. 100012 - 100012

Published: March 26, 2024

We perform direct numerical simulations to study the effect of increasing airflow rate on CO2 concentration in downflow and displacement ventilation a room with one occupant. Often, is used as proxy for bio-aerosols respiratory droplets, therefore, tracking strategies can be useful understand quantify risk spread communicable illnesses. At low moderate rates, flow setup not mixed, but stratified. The upper lower layers determined by strength thermal plume originating from provide simple theoretical model predict height stratified interface, volumetric flux ascending plume, layers. very high well-mixed average predicted mixing assumption. demonstrate that at more effectively maintains concentrations layer compared ventilation.

Language: Английский

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Toward Standardized Aerovirology: A Critical Review of Existing Results and Methodologies

Environmental Science & Technology, Journal Year: 2024, Volume and Issue: 58(8), P. 3595 - 3608

Published: Feb. 14, 2024

Understanding the airborne survival of viruses is important for public health and epidemiological modeling potentially to develop mitigation strategies minimize transmission pathogens. Laboratory experiments typically involve investigating effects environmental parameters on viability or infectivity a target virus. However, conflicting results among studies are common. Herein, 34 aerovirology were compared identify links between compositional viruses. While specific experimental apparatus was not factor in variability reported results, it determined that procedure major contributed discrepancies results. The most significant contributor poorly defined initial viable virus concentration aerosol phase, causing many measure rapid inactivation, which occurs quickly after particle generation, leading Consistently, measured their reference minutes aerosolization higher at subsequent times, indicates there an loss captured these studies. composition particles carry also found be viruses; however, mechanisms this effect unknown. Temperature aerosol-phase viability, but lack directly compare temperature phase bulk phase. There need repeated measurements different research groups under identical conditions both assess degree attempt better understand already published data. Lack standardization has hindered ability quantify differences studies, we provide recommendations future These as follows: measuring using "direct method"; use equipment maximizes time resolution; all losses appropriately; perform, least, 5- 10-min sample, if possible; report clearly suspension; gas throughout experiment. Implementing will address oversights existing literature produce data can more easily quantitatively compared.

Language: Английский

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Collagen Tubular Airway‐on‐Chip for Extended Epithelial Culture and Investigation of Ventilation Dynamics

Small, Journal Year: 2024, Volume and Issue: 20(27)

Published: March 3, 2024

Abstract The lower respiratory tract is a hierarchical network of compliant tubular structures that are made from extracellular matrix proteins with wall lined by an epithelium. While microfluidic airway‐on‐a‐chip models incorporate the effects shear and stretch on epithelium, week‐long air‐liquid‐interface culture at physiological stresses, circular cross‐section, compliance native airway walls have yet to be recapitulated. To overcome these limitations, collagen tube‐based model presented. lumen confluent epithelium during two‐week continuous perfusion warm, humid air while presenting medium outside compensating for evaporation. recapitulates human small airways in composition mechanical microenvironment, allowing first time dynamic studies elastocapillary phenomena associated regular breathing ventilation, as well their impacts A case study reveales increasing damage repetitive collapse reopening cycles opposed overdistension, suggesting expiratory flow resistance reduce atelectasis. expected promote systematic comparisons between different clinically used ventilation strategies and, more broadly, enhance organ‐on‐a‐chip platforms variety tissues.

Language: Английский

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