Measuring interpersonal transmission of expiratory droplet nuclei in close proximity

2021 ◽  
pp. 1420326X2110296
Author(s):  
Linzhi Fu ◽  
Peter V. Nielsen ◽  
Yi Wang ◽  
Li Liu
Keyword(s):  
Disease Transmission ◽  
Short Range ◽  
Close Contact ◽  
Measurement Techniques ◽  
Transmission Risk ◽  
Interpersonal Distance ◽  
Airborne Transmission ◽  
Face To Face ◽  
Close Proximity ◽  
Droplet Nuclei

Increasing evidence supports the significant role of short-range airborne transmission of viruses when in close contact with a source patient. A full-scale ventilated room (Cleanliness: ISO 14644–1 Class 5) and two face-to-face standing breathing thermal manikins were used to simulate a source individual and a susceptible person. Monodisperse particle generation and measurement techniques were used to evaluate the effect of virus-laden droplet nuclei size on short-range airborne transmission risk. We analysed four particle sizes (1.0, 1.5, 2.5, and 5.0 µm) to simulate the transport of exhaled droplet nuclei within an interpersonal distance of 0.5 m. The results indicated that the size distribution of airborne droplet nuclei could significantly influence transmission, with the inhalation fraction decreasing with increasing droplet nuclei size. Additionally, results showed that proximity to the source manikin could influence transmission. Inhalation fraction decreased with increasing interpersonal distance, fitting well with the 1/ d rule of droplet nuclei concentration decay. Our findings improve the understanding of the mechanism of the disease transmission.

scholarly journals Risk assessment for long and short range airborne transmission of SARS-CoV-2, indoors and outdoors, using carbon dioxide measurements.

2021 ◽  
Author(s):  
Florian Poydenot ◽  
Ismael Abdourahamane ◽  
Elsa Caplain ◽  
Samuel Der ◽  
Jacques Haiech ◽  
...  
Keyword(s):  
Public Health ◽  
Health Policy ◽  
Public Health Policy ◽  
Short Range ◽  
Epidemiological Data ◽  
Public Spaces ◽  
Viral Transmission ◽  
Transmission Risk ◽  
Reproduction Rate ◽  
Airborne Transmission

A quantitative analysis of the viral transmission risk in public spaces al- lows us to identify the dominant mechanisms that a proactive public health policy can act upon to reduce risk, and to evaluate the reduction of risk that can be obtained. The contribution of public spaces to the propa- gation of SARS-CoV-2 can be reduced to a level necessary for a declining epidemic, i.e. an overall reproduction rate below one. Here, we revisit the quantitative assessment of indoor and outdoor transmission risk. We show that the long-range aerosol transmission is controlled by the flow rate of fresh air and by the mask filtering quality, and is quantitatively re- lated to the CO2 concentration, regardless the room volume and the num- ber of people. The short-range airborne transmission is investigated ex- perimentally using dedicated dispersion experiments performed in two shopping malls. Exhaled aerosols are dispersed by turbulent draughts in a cone, leading to a concentration inversely proportional to the squared dis- tance and to the flow velocity. We show that the average infection dose, called the viral quantum, can be determined from epidemiological data in a manner consistent with biological experimental data. Practical implications. The results provide quantitative guidance useful for making rational public health policy decisions to prevent the dominant routes of viral transmission through reinforced ventilation, air purification, mechanical dispersion using fans, and incentivizing the wear- ing of correctly fitted, quality facial masks (surgical masks, possibly cov- ered by another fabric mask, or non-medical FFP2 masks). Taken to- gether, such measures significantly reduce the airborne transmission risk of SARS-CoV-2.

scholarly journals Global shifts in mammalian population trends reveal key predictors of virus spillover risk

2020 ◽  
Vol 287 (1924) ◽  
pp. 20192736 ◽  
Author(s):  
Christine K. Johnson ◽  
Peta L. Hitchens ◽  
Pranav S. Pandit ◽  
Julie Rushmore ◽  
Tierra Smiley Evans ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Close Contact ◽  
Anthropogenic Activities ◽  
Mammalian Species ◽  
Species Abundance ◽  
Zoonotic Disease ◽  
Wildlife Habitat ◽  
Transmission Risk ◽  
Population Declines ◽  
Zoonotic Viruses

Emerging infectious diseases in humans are frequently caused by pathogens originating from animal hosts, and zoonotic disease outbreaks present a major challenge to global health. To investigate drivers of virus spillover, we evaluated the number of viruses mammalian species have shared with humans. We discovered that the number of zoonotic viruses detected in mammalian species scales positively with global species abundance, suggesting that virus transmission risk has been highest from animal species that have increased in abundance and even expanded their range by adapting to human-dominated landscapes. Domesticated species, primates and bats were identified as having more zoonotic viruses than other species. Among threatened wildlife species, those with population reductions owing to exploitation and loss of habitat shared more viruses with humans. Exploitation of wildlife through hunting and trade facilitates close contact between wildlife and humans, and our findings provide further evidence that exploitation, as well as anthropogenic activities that have caused losses in wildlife habitat quality, have increased opportunities for animal–human interactions and facilitated zoonotic disease transmission. Our study provides new evidence for assessing spillover risk from mammalian species and highlights convergent processes whereby the causes of wildlife population declines have facilitated the transmission of animal viruses to humans.

scholarly journals Device for Suppression of Aerosol Transfer in Close Proximity Settings

COVID ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 394-402
Author(s):  
Yicheng Bao ◽  
Loïc Anderegg ◽  
Sean Burchesky ◽  
John M. Doyle
Keyword(s):  
Respiratory Disease ◽  
Disease Transmission ◽  
Potential Application ◽  
Small Space ◽  
Large Space ◽  
Face To Face ◽  
Close Proximity ◽  
Optically Transparent ◽  
Filter Unit ◽  
University Setting

Here we present a device that suppresses transfer of aerosol between nearby seating areas through the use of optically transparent, sound transmitting barriers and HEPA fan filter unit (FFU). A potential application of this device is to lower the risk of respiratory disease transmission in face-to-face, maskless meetings between individuals in a university setting. We evaluate overall aerosol transmission between users of the device. This is done for two different physical settings: a large space, such as a library, and a small space, such as an enclosed study room. We find that the device can provide lower aerosol transmission compared to the typical transmission between two individuals wearing surgical face masks separated by six feet.

scholarly journals Characteristics of airborne transmission under stratum ventilation

2019 ◽  
Vol 111 ◽  
pp. 02019
Author(s):  
Tao Huang ◽  
Zhengtao Ai ◽  
Arsen Melikov
Keyword(s):  
Air Distribution ◽  
Breathing Zone ◽  
Relative Positioning ◽  
Exposure Risk ◽  
Tracer Gas ◽  
Airborne Transmission ◽  
Climate Chamber ◽  
Distribution Method ◽  
Close Proximity ◽  
Droplet Nuclei

The objective of this study is to investigate the characteristics of airborne spread of exhaled droplet nuclei between two occupants in a space conditioned by a horizontal air distribution method, known as stratum ventilation. Experiments were conducted in a full-scale climate chamber. Two breathing thermal manikins were used to simulate a standing infected person and a standing exposed person, respectively. Tracer gas (N2O) was added into the air exhaled by the infected manikin. The tracer gas concentrations in the air inhaled by the exposed manikin and at the ventilation exhaust were continuously monitored. ACH was kept at 2 h-1. The variables in the experiments include the positioning of the manikins, the distance between manikins, and the room air temperature. The horizontal supply airflow to the breathing zone strongly intensifies the mixing between the flow of exhalation and the room air, which reduces the exposure risk of occupants at close proximity and flattens the risk-distance curves. The homogenization of concentration weakens considerably the importance of the relative positioning and location of the infected and exposed persons. All those characteristics of airborne transmission may not be maintained, however, if the horizontal supply jet does not interact directly with the occupants. The findings from this study are intended to contribute for better understanding of airborne transmission indoors.

scholarly journals Review of SARS-CoV-2 and Conjunctivitis: Ophthalmologists Be Safe

2020 ◽  
Author(s):  
Mona P Sune ◽  
Pradeep Sune ◽  
Vishal Kalode
Keyword(s):  
Health Care Workers ◽  
Disease Transmission ◽  
Close Contact ◽  
Wuhan City ◽  
Protection Measures ◽  
Care Workers ◽  
Route Of Transmission ◽  
Close Proximity ◽  
Aerosol Infection ◽  
Respiratory Droplets

The COVID-19 or the Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2) has become pandemic with its origin in Wuhan, city of China. Within few weeks, it became a global health threat involving more than 200 countries. Though the main route of transmission is by respiratory droplets; trans-conjunctival aerosol infection is a known mode of disease transmission. Patients with COVID-19 conjunctivitis have the transmissible virus in the tears. Close contact during ophthalmic procedures poses the risk of patient to ophthalmologist disease transmission. Conjunctivitis may be the first symptom of COVID-19. In context to this and the close proximity of an ophthalmologist and Health Care Workers (HCW) with the patient, and the nature of work, standard infection protection measures guidelines have been given by prominent healthcare societies.

scholarly journals Airborne transmission during short-term events under stratum ventilation

2019 ◽  
Vol 111 ◽  
pp. 01098
Author(s):  
Kaho Hashimoto ◽  
Zhengtao Ai ◽  
Arsen Melikov
Keyword(s):  
Steady State ◽  
Separation Distance ◽  
Control Measures ◽  
Exposure Index ◽  
Tracer Gas ◽  
Short Term ◽  
Airborne Transmission ◽  
Face To Face ◽  
Droplet Nuclei

Past studies on airborne spread of expiratory droplet nuclei between occupants were focused on long-term exposure under steady-state conditions. However, exposure during short-term events can be widely found in practice, e.g. medical examination or short meeting. Airborne transmission during short-term events under stratum ventilation was examined experimentally in this study. Two breathing thermal manikins were employed to simulate a standing infected person and a standing exposed person. The manikins were placed face-to-face and face-to-back to reproduce the exposure conditions with the highest and the lowest risk, respectively. Tracer gas was dosed into the air exhaled by the “infected” manikin to simulate the droplet nuclei. A newly developed average exposure index was used to evaluate the exposure risk. The time-averaged exposure index increases over time, but the increasing rate depends strongly on the duration of exposure time, e.g., the exposure index increases much faster during the first 5 minutes than during the period after 5 minutes. The exposure index during short-term events does not always decrease with the increase of separation distance. These findings imply that the control measures formulated based on steady-state conditions are not necessarily effective to short-term events.

scholarly journals A video-based analysis of situations bearing the risk of respiratory disease transmission during football matches

2021 ◽  
Author(s):  
Oliver Faude ◽  
Simon Müller ◽  
Sebastian Schreiber ◽  
Jonas Müller ◽  
Lukas Nebiker ◽  
...  
Keyword(s):  
Respiratory Disease ◽  
Disease Transmission ◽  
Close Contact ◽  
Pathogen Transmission ◽  
Field Of View ◽  
Respiratory Pathogen ◽  
Face To Face ◽  
Football Match ◽  
Droplet Production ◽  
Different Levels

We aimed to analyze the number and type of contacts involving the risk of respiratory disease transmission during football match play.We analysed videos of 50 matches from different levels of play (professional, amateur, youth). Two reviewers evaluated the contacts of all players in the field of view in each match. We focused on between-player contacts (duels), crowding, actions with potentially increased aerosol and droplet production (speaking, shouting, spitting) and within-player hand-to-head contacts. We categorized the duels with direct contact into frontal (face-to-face) and other ones and measured contact duration.The number of between-player contacts were similar between playing levels (median 28.3 [IQR 22.6,33] contacts per player-hour). Frontal contacts summed up to 8% of all contacts. Contacts involving the head occurred on average less than once per player during a 90-min match with none in frontal positioning and none lasting longer than 3 s. Crowding included on average between two and six players and the duration was mostly less than 10 s. Only goal celebrations lasted more than twice as long in professionals (median 21.4 s [IQR 13.8,24.8]) and amateurs (median 18.6 s [IQR 16.3,22]) compared to youth players (median 8.9 s [IQR 0,14.8]). Aerosol and droplet producing activities were three to four times more frequent in adult compared to youth players.Our results suggest that the risk of respiratory pathogen transmission is low during football matches. This conclusion is based on the finding that most close contact situations are of short duration and on the fact that it is mainly an outdoor sport.

scholarly journals Peering inside a cough or sneeze to explain enhanced airborne transmission under dry weather

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kai Liu ◽  
Majid Allahyari ◽  
Jorge S. Salinas ◽  
Nadim Zgheib ◽  
S. Balachandar
Keyword(s):  
High Fidelity ◽  
Substantial Variation ◽  
Ambient Conditions ◽  
Airborne Transmission ◽  
Social Distancing ◽  
Virtual Experiments ◽  
Long Time ◽  
Simulation Results ◽  
High Fidelity Simulations ◽  
Droplet Nuclei

AbstractHigh-fidelity simulations of coughs and sneezes that serve as virtual experiments are presented, and they offer an unprecedented opportunity to peer into the chaotic evolution of the resulting airborne droplet clouds. While larger droplets quickly fall-out of the cloud, smaller droplets evaporate rapidly. The non-volatiles remain airborne as droplet nuclei for a long time to be transported over long distances. The substantial variation observed between the different realizations has important social distancing implications, since probabilistic outlier-events do occur and may need to be taken into account when assessing the risk of contagion. Contrary to common expectations, we observe dry ambient conditions to increase by more than four times the number of airborne potentially virus-laden nuclei, as a result of reduced droplet fall-out through rapid evaporation. The simulation results are used to validate and calibrate a comprehensive multiphase theory, which is then used to predict the spread of airborne nuclei under a wide variety of ambient conditions.

scholarly journals Teleconsultation and Teletreatment Protocol to Diagnose and Manage Patients with Benign Paroxysmal Positional Vertigo (BPPV) during the COVID-19 Pandemic

2021 ◽  
Vol 25 (01) ◽  
pp. e141-e149
Author(s):  
Renato Gonzaga Barreto ◽  
Darío Andrés Yacovino ◽  
Lázaro Juliano Teixeira ◽  
Mayanna Machado Freitas
Keyword(s):  
Disease Transmission ◽  
Benign Paroxysmal Positional Vertigo ◽  
Good Clinical Practice ◽  
Relevant Information ◽  
Remote Access ◽  
Vestibular Disorder ◽  
Face To Face ◽  
Positional Vertigo ◽  
Video And Audio ◽  
Paroxysmal Positional Vertigo

Abstract Introduction Telehealth consists in the application of technology to provide remote health service. This resource is considered safe and effective and has attracted an exponential interest in the context of the COVID pandemic. Expanded to dizzy patients, it would be able to provide diagnosis and treatment, minimizing the risk of disease transmission. Benign paroxysmal positional vertigo (BPPV) is the most common vestibular disorder. The diagnosis typically rests on the description of the symptoms along with the nystagmus observed at a well-established positional testing. Objectives The aim of the present study was to propose a teleconsultation and teletreatment protocol to manage patients with BPPV during the COVID-19 pandemic. Methods Specialists in the vestibular field met through remote access technologies to discuss the best strategy to manage BPPV patients by teleconsultation and teletreatment system. Additionally, several scientific sources were consulted. Technical issues, patient safety, and clinical assessment were independently analyzed. All relevant information was considered in order to design a clinical protocol to manage BPPV patients in the pandemic context. Results Teleconsultation for BPPV patients requires a double way (video and audio) digital system. An adapted informed consent to follow good clinical practice statements must be considered. The time, trigger and target eye bedside examination (TiTRaTe) protocol has proven to be a valuable first approach. The bow and lean test is the most rational screening maneuver for patients with suspected positional vertigo, followed by most specific maneuvers to diagnostic the sub-variants of BPPV. Conclusion Although with limited evidence, teleconsultation and teletreatment are both reasonable and feasible strategies for the management of patients with BPPV in adverse situations for face-to-face consultation.

scholarly journals Livestock movement informs the risk of disease spread in traditional production systems in East Africa

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Divine Ekwem ◽  
Thomas A. Morrison ◽  
Richard Reeve ◽  
Jessica Enright ◽  
Joram Buza ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Production Systems ◽  
Control Strategies ◽  
Herd Size ◽  
Transmission Risk ◽  
Disease Spread ◽  
Transmission Potential ◽  
Spatial And Temporal Scales ◽  
Transmission Distance ◽  
Risk Of Disease

AbstractIn Africa, livestock are important to local and national economies, but their productivity is constrained by infectious diseases. Comprehensive information on livestock movements and contacts is required to devise appropriate disease control strategies; yet, understanding contact risk in systems where herds mix extensively, and where different pathogens can be transmitted at different spatial and temporal scales, remains a major challenge. We deployed Global Positioning System collars on cattle in 52 herds in a traditional agropastoral system in western Serengeti, Tanzania, to understand fine-scale movements and between-herd contacts, and to identify locations of greatest interaction between herds. We examined contact across spatiotemporal scales relevant to different disease transmission scenarios. Daily cattle movements increased with herd size and rainfall. Generally, contact between herds was greatest away from households, during periods with low rainfall and in locations close to dipping points. We demonstrate how movements and contacts affect the risk of disease spread. For example, transmission risk is relatively sensitive to the survival time of different pathogens in the environment, and less sensitive to transmission distance, at least over the range of the spatiotemporal definitions of contacts that we explored. We identify times and locations of greatest disease transmission potential and that could be targeted through tailored control strategies.

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