Face Coverings and Respiratory Tract Droplet Dispersion

Respiratory droplets are the primary transmission route for SARS-CoV-2. Evidence suggests that virus transmission can be reduced by face coverings, but robust evidence for how mask usage might affect safe distancing parameters is lacking. Accordingly, we investigate the effectiveness of surgical masks and single-layer cotton masks on mitigating dispersion of large respiratory droplets (i.e. non aerosol). We tested a manikin ejecting fluorescent droplets and human volunteers in speaking and coughing conditions. We quantified the number of droplets in flight using laser sheet illumination and UV-light for those that had landed at table height at up to 2m. For human volunteers, expiratory droplets were caught on a microscope slide 5cm from the mouth. Whether manikin or human, wearing a face covering decreased the number of projected droplets by >1000-fold. We estimated that a person standing 2m from someone coughing without a mask is exposed to over 1000 times more respiratory droplets than from someone standing 5 cm away wearing a basic single layer mask. Our results indicate that face coverings show consistent efficacy at blocking respiratory droplets. If aerosol transmission is later determined to be a significant driver of infection, then our findings may overestimate the effectiveness of face coverings.

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Face coverings and respiratory tract droplet dispersion

Royal Society Open Science ◽

10.1098/rsos.201663 ◽

2020 ◽

Vol 7 (12) ◽

pp. 201663

Author(s):

Lucia Bandiera ◽

Geethanjali Pavar ◽

Gabriele Pisetta ◽

Shuji Otomo ◽

Enzo Mangano ◽

...

Keyword(s):

Respiratory Tract ◽

Uv Light ◽

Laser Sheet ◽

Virus Transmission ◽

Single Layer ◽

Social Distancing ◽

Human Volunteers ◽

Respiratory Droplets ◽

Primary Transmission ◽

Robust Evidence

Respiratory droplets are the primary transmission route for SARS-CoV-2, a principle which drives social distancing guidelines. Evidence suggests that virus transmission can be reduced by face coverings, but robust evidence for how mask usage might affect safe distancing parameters is lacking. Accordingly, we set out to quantify the effects of face coverings on respiratory tract droplet deposition. We tested an anatomically realistic manikin head which ejected fluorescent droplets of water and human volunteers, in speaking and coughing conditions without a face covering, or with a surgical mask or a single-layer cotton face covering. We quantified the number of droplets in flight using laser sheet illumination and UV-light for those that had landed at table height at up to 2 m. For human volunteers, expiratory droplets were caught on a microscope slide 5 cm from the mouth. Whether manikin or human, wearing a face covering decreased the number of projected droplets by less than 1000-fold. We estimated that a person standing 2 m from someone coughing without a mask is exposed to over 10 000 times more respiratory droplets than from someone standing 0.5 m away wearing a basic single-layer mask. Our results indicate that face coverings show consistent efficacy at blocking respiratory droplets and thus provide an opportunity to moderate social distancing policies. However, the methodologies we employed mostly detect larger (non-aerosol) sized droplets. If the aerosol transmission is later determined to be a significant driver of infection, then our findings may overestimate the effectiveness of face coverings.

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Making cotton face masks extra-protective by use of impervious cloth as the front layer to restrict flow of aerosols and droplets

10.1101/2020.07.30.20165563 ◽

2020 ◽

Author(s):

Priyanka L Shahane-Kapse ◽

Moreshwar R Shende ◽

Sumit Kar ◽

Pradeep Deshmukh ◽

Dhiraj Bhandari ◽

...

Keyword(s):

Single Layer ◽

Middle Layer ◽

Face Mask ◽

The Other ◽

Outer Side ◽

Carbol Fuchsin ◽

Triple Layer ◽

Impervious Layer ◽

Surgical Masks ◽

The Face

Introduction: One of the important measures to prevent spread of COVID-19 in community is use of face mask. Though the debate is going on regarding the airborne transmission of SARS-CoV-2 it makes reasonable point for universal use of face masks. A large variety of face masks are available in the market or people can make their own using household items. The efficacy of masks depends upon the type of cloth and number of layers of the cloth. Material and methods: We have created an innovative mask with two layers of cotton and an impervious layer. The impervious layer made from polypropylene coated with polyurethane was applied on the outer side in the middle half of the mask in front of mouth and nose. The efficacy of this test mask was measured against N95FFR (reference standard), triple layer surgical masks and single layer cotton mask. A manikin was used wearing these masks/respirator and aerosols/droplets of diluted red colored carbol fuchsin and fluorescent Auramine O were sprayed from distance of 1m and 2m. We also tested use of face shield. Both macroscopic and microscopic examination of the dissected masks and respirator was performed. Results: The N95FFR was able to block the aerosols/droplets by its front layer. One triple layer surgical mask showed microscopic presence of stain in its innermost layer while the other blocked it with middle layer. The single layer cotton mask was not able to protect as we observed stain on the face itself. The test mask blocked most of the stain on impervious layer and also on the front cotton layer on lateral sides, where impervious layer was absent. When fluorescent stain was used, ultraviolet examination demonstrated that the whole area covered by test mask was clean while the other non covered area was fluorescent. Conclusion: We believe that our innovation can be used in the community as well as in general areas of the hospital like, offices, labs, etc. and can be a better alternative to single use triple layer surgical masks. Further testing may be done by other organizations to rule out bias in our study.

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Antiviral Coatings as Continuously Active Disinfectants

10.5772/intechopen.101752 ◽

2021 ◽

Author(s):

Luisa A. Ikner ◽

Charles P. Gerba

Keyword(s):

Titanium Dioxide ◽

Free Radicals ◽

Nucleic Acids ◽

Visible Light ◽

Quaternary Ammonium ◽

Uv Light ◽

Virus Transmission ◽

Antimicrobial Surfaces ◽

Bacteria And Fungi ◽

Growth Of Bacteria

Antimicrobial surfaces and coatings have been available for many decades and have largely been designed to kill or prevent the growth of bacteria and fungi. Antiviral coatings have become of particular interest more recently during the COVID-19 pandemic as they are designed to act as continuously active disinfectants. The most studied antiviral coatings have been metal-based or are comprised of silane quaternary ammonium formulations. Copper and silver interact directly with proteins and nucleic acids, and influence the production of reactive free radicals. Titanium dioxide acts as a photocatalyst in the presence of water and oxygen to produce free radicals in the presence of UV light or visible light when alloyed with copper or silver. Silane quaternary ammonium formulations can be applied to surfaces using sprays or wipes, and are particularly effective against enveloped viruses. Continuously active disinfectants offer an extra barrier against fomite-mediated transmission of respiratory and enteric viruses to reduce exposure between routine disinfection and cleaning events. To take advantage of this technology, testing methods need to be standardized and the benefits quantified in terms of reduction of virus transmission.

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Viruses such as SARS-CoV-2 can be partially shielded from UV radiation when in particles generated by sneezing or coughing: Numerical simulations

10.1101/2020.11.19.20233437 ◽

2020 ◽

Author(s):

David C. Doughty ◽

Steven C. Hill ◽

Daniel W. Mackowski

Keyword(s):

Numerical Modeling ◽

Optical Properties ◽

Numerical Simulations ◽

Uv Radiation ◽

Uv Light ◽

Spherical Particles ◽

Brownian Diffusion ◽

Uv Illumination ◽

Light Intensities ◽

Respiratory Droplets

AbstractUV radiation can inactivate viruses such as SARS-CoV-2. However, designing effective UV germicidal irradiation (UVGI) systems can be difficult because the effects of dried respiratory droplets and other fomites on UV light intensities are poorly understood. Numerical modeling of UV intensities inside virus-containing particles on surfaces can increase understanding of these possible reductions in UV intensity. We model UV intensities within spherical approximations of virions randomly positioned within spherical particles. The model virions and dried particles have sizes and optical properties to approximate SARS-CoV-2 and dried particles formed from respiratory droplets, respectively. Wavelengths used are 260 nm (germicidal UVC) and 302 nm (solar UVB). In 5- and 9-μm diameter particles on a surface, illuminated by 260-nm UV light from a direction perpendicular to the surface, 10% and 18% (respectively) of simulated virions are exposed to intensities less than 1/100th of intensities in individually exposed virions (i.e., they are partially shielded). Even for 302-nm light, where the absorption is small, 11% of virions in 9-µm particles have exposures 1/100th those of individually exposed virions. Calculated results show that shielding of virions in a particle can be strongly reduced by illuminating a particle either from multiple widely separated incident directions, or by illuminating a particle rotating in air (because of turbulence, Brownian diffusion, etc.) for a time sufficient to rotate through all orientations with respect to the UV illumination. Because highly UV-reflective paints and surfaces can increase the angular ranges of illumination, they appear likely to be useful for reducing shielding of virions.

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Transmission Modes of COVID-19: A Systematic Review

Infectious Disorders - Drug Targets ◽

10.2174/1871526520666201116095934 ◽

2020 ◽

Vol 20 ◽

Author(s):

Esmaeil Mehraeen ◽

Mohammad Amin Salehi ◽

Farzane Behnezhad ◽

Hamed Rezakhani Moghaddam ◽

SeyedAhmad SeyedAlinaghi

Keyword(s):

Systematic Review ◽

Virus Transmission ◽

Careful Consideration ◽

Fecal Excretion ◽

Current Evidence ◽

Inclusion Criteria ◽

Human Environment ◽

Transmission Modes ◽

High Prevalence ◽

Respiratory Droplets

Background: The Coronavirus disease 19 (COVID-19) is a highly transmittable viral infection that initiated in Wuhan, China and has spread around the world. The high prevalence and spread ways of COVID-19 have become an international challenge that requires careful consideration. We aimed to review the current evidence of COVID-19 transmission modes. Methods: This study was a systematic review that was done to identify current evidence on transmission modes of COVID19. We searched selected keywords in six important databases to discover related sources on the main objective of the study. To identify studies meeting the inclusion criteria, the authors screened the titles and abstracts of retrieved documents. The appropriate articles were selected and their results were discussed to make the final inclusion. Results: We identified five potential transmission modes of COVID-19 including airborne, droplet, contact with contaminated surfaces, oral and fecal secretions. Furthermore, some studies have pointed out other modes of virus transmission, such as person to person, and direct contact with animals. Conclusion: Droplet and contact with contaminated surfaces were the most frequent transmission modes of COVID-19. Fecal excretion, environmental contamination, and fluid pollution might contribute to a viral transmission. The possibility of fecal transmission of COVID-19 has implications, especially in areas with poor sanitation and the environmental pollution can be caused by patients with SARS-CoV-2 through respiratory droplets and feces, subsequently, the human environment will change to a potential medium of virus transmission.

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Frequency of Instrument, Environment, and Laboratory Technologist Contamination during Routine Diagnostic Testing of Infectious Specimens

Journal of Clinical Microbiology ◽

10.1128/jcm.00225-18 ◽

2018 ◽

Vol 56 (6) ◽

Cited By ~ 5

Author(s):

Melanie L. Yarbrough ◽

Jennie H. Kwon ◽

Meghan A. Wallace ◽

Tiffany Hink ◽

Angela Shupe ◽

...

Keyword(s):

Laboratory Testing ◽

Clinical Laboratory ◽

Uv Light ◽

Diagnostic Testing ◽

Virus Transmission ◽

Pathogen Transmission ◽

Safety Practices ◽

Bacteriophage Ms2 ◽

Laboratory Workers ◽

Laboratory Contamination

ABSTRACTLaboratory testing to support the care of patients with highly infectious diseases may pose a risk for laboratory workers. However, data on the risk of virus transmission during routine laboratory testing conducted using standard personal protective equipment (PPE) are sparse. Our objective was to measure laboratory contamination during routine analysis of patient specimens. Remnant specimens were spiked with the nonpathogenic bacteriophage MS2 at 1.0 × 107PFU/ml, and contamination was assessed using reverse transcriptase PCR (RT-PCR) for MS2. Specimen containers were exteriorly coated with a fluorescent powder to enable the visualization of gross contamination using UV light. Testing was performed by two experienced laboratory technologists using standard laboratory PPE and sample-to-answer instrumentation. Fluorescence was noted on the gloves, bare hands, and laboratory coat cuffs of the laboratory technologist in 36/36 (100%), 13/36 (36%), and 4/36 (11%) tests performed, respectively. Fluorescence was observed in the biosafety cabinet (BSC) in 8/36 (22%) tests, on test cartridges/devices in 14/32 (44%) tests, and on testing accessory items in 29/32 (91%) tests. Fluorescence was not observed on or in laboratory instrumentation or adjacent surfaces. In contrast to fluorescence detection, MS2 detection was infrequent (3/286 instances [1%]) and occurred during test setup for the FilmArray instrument and on FilmArray accessory equipment. The information from this study may provide opportunities for the improvement of clinical laboratory safety practices so as to reduce the risk of pathogen transmission to laboratory workers.

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Jet Fans in the Underground Car Parks and Virus Transmission

10.21203/rs.3.rs-93879/v1 ◽

2020 ◽

Author(s):

Ata Nazari ◽

Moharram Jafari ◽

Naser Rezaei ◽

Farzad Taghizadeh-Hesary

Keyword(s):

Numerical Simulation ◽

Severe Acute Respiratory Syndrome ◽

Virus Transmission ◽

Quantitative Understanding ◽

Novel Coronavirus ◽

Respiratory Droplets

Abstract Jet fans are increasingly preferred over traditional ducted systems as a means of ventilating pollutants from large spaces such as underground car parks. The spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) -which causes novel coronavirus disease (COVID-19)- through the jet fans in the underground car parks has been considered a matter of key concern. A quantitative understanding of the propagation of respiratory droplets/particles/aerosols containing the virus is important. However, to date, studies are yet to demonstrate the viral (e.g. SARS-CoV-2) transmission in the underground car parks equipped with jet fans. In this paper, the numerical simulation has been performed to assess the eﬀects of jet fans on the spreading of viruses inside the underground car parks.

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How effective are face coverings in reducing transmission of COVID-19?

10.1101/2020.12.01.20241992 ◽

2020 ◽

Cited By ~ 1

Author(s):

Joshua F. Robinson ◽

Ioatzin Rios de Anda ◽

Fergus J. Moore ◽

Florence K. A. Gregson ◽

Jonathan P. Reid ◽

...

Keyword(s):

Size Distribution ◽

Material Properties ◽

Filtration Efficiency ◽

Controversial Issues ◽

Airborne Transmission ◽

Viral Loads ◽

Surgical Masks ◽

Highly Effective ◽

Respiratory Droplets ◽

Droplet Transmission

In the COVID–19 pandemic, among the more controversial issues is the use of face coverings. To address this we show that the underlying physics ensures particles with diameters ≳1 µm are efficiently filtered out by a simple cotton or surgical mask. For particles in the submicron range the efficiency depends on the material properties of the masks, though generally the filtration efficiency in this regime varies between 30 to 60 % and multi-layered cotton masks are expected to be comparable to surgical masks.Respiratory droplets are conventionally divided into coarse droplets (≳5–10 µm) responsible for droplet transmission and aerosols (≳ 5–10 µm) responsible for airborne transmission. Masks are thus expected to be highly effective at preventing droplet transmission, with their effectiveness limited only by the mask fit, compliance and appropriate usage. By contrast, knowledge of the size distribution of bioaerosols and the likelihood that they contain virus is essential to understanding their effectiveness in preventing airborne transmission. We argue from literature data on SARS-CoV-2 viral loads that the finest aerosols (≳ 1 µm) are unlikely to contain even a single virion in the majority of cases; we thus expect masks to be effective at reducing the risk of airborne transmission in most settings.

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Bacteria Filtration Efficiency of Different Face Masks Worn during COVID-19 Pandemic in North-Eastern Tanzania: An In Vitro Study

10.20944/preprints202010.0574.v1 ◽

2020 ◽

Author(s):

Marianne Gnanamuttupulle ◽

Shilanaiman Hilary Ntundu ◽

Oliver Henke ◽

Abias Anthon Moshi ◽

David Msuya ◽

...

Keyword(s):

Double Layer ◽

Single Layer ◽

In Vitro Study ◽

Filtration Efficiency ◽

Cotton Cloth ◽

Bacterial Suspension ◽

Surgical Masks ◽

North Eastern ◽

N95 Respirators

Increased demand for wearing face masks, lack of surgical masks and N95 respirators during the coronavirus pandemic created alternative needs for cloth masks. Therefore, to determine filtration efficacy, reusability and duration of wearing new and hand washed cloth masks, the bacteria filtration efficacy was tested using Staphylococcus aureus and Escherichia coli. Cotton cloth masks; single layer without pleats and with pleats, double layer with canvas filter in the middle, double layer with stiff filter in the middle, double layer with pleats on both sides and locally made and imported surgical masks and N95 respirators were used. Bacterial suspension was sprayed over outer surface and swabbed from inner surface at 0hrs, 4thhr, 8thhr and 12thhr. Similar procedure was performed to hand washed and ironed cotton cloth masks. After 24 hours of incubation, single layer without pleats and with pleats had no filtration efficacy(0-100%). Double layer with stiff filter in the middle and double layer with pleats on both sides had higher filtration efficacy(99.96-100%), this filtration efficacy remained up to three occasions of hand washing with soap and water, conferring protection up to 12hours. Filtration efficacy of surgical masks made locally, imported and N95 respirators were 90-100%, 99.99-100%, and 99.99-100% respectively.

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Low-cost measurement of facemask efficacy for filtering expelled droplets during speech

10.1101/2020.06.19.20132969 ◽

2020 ◽

Cited By ~ 3

Author(s):

Emma P. Fischer ◽

Martin C. Fischer ◽

David Grass ◽

Isaac Henrion ◽

Warren S. Warren ◽

...

Keyword(s):

Measurement Method ◽

Optical Measurement ◽

Low Cost ◽

Rapid Evaluation ◽

Infected Person ◽

Surgical Masks ◽

Cost Measurement ◽

Respiratory Droplets ◽

Optical Measurement Method

AbstractMandates for mask use in public during the recent COVID-19 pandemic, worsened by global shortage of commercial supplies, have led to widespread use of homemade masks and mask alternatives. It is assumed that wearing such masks reduces the likelihood for an infected person to spread the disease, but many of these mask designs have not been tested in practice. We have applied a simple optical measurement method to evaluate the efficacy of masks to reduce the transmission of respiratory droplets during regular speech. We compare a variety of commonly available mask types and observe that some mask types approach the performance of standard surgical masks, while some mask alternatives, such as neck fleece or bandanas, offer very little protection. Our measurement setup is inexpensive and can be built and operated by non-experts, allowing for rapid evaluation of mask performance during speech, sneezing, or coughing.

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