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Open accessJournal ArticleDOI: 10.1080/02786826.2020.1846679

Assessing the effectiveness of using various face coverings to mitigate the transport of airborne particles produced by coughing indoors

04 Mar 2021-Aerosol Science and Technology (Taylor & Francis)-Vol. 55, Iss: 3, pp 332-339
Abstract: Exposure to respiratory droplets contributes greatly to the spread of SARS-CoV-2 virus during the COVID-19 pandemic. This study investigates the effectiveness of various face coverings to reduce co...

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Open access
10 Mar 2020-
Topics: Dashboard (business) (69%)

616 Citations


Open accessPosted ContentDOI: 10.1101/2020.11.18.20233353
Abstract: We evaluated the effectiveness of 11 face coverings for material filtration efficiency, inward protection efficiency on a manikin, and outward protection efficiency on a manikin. At the most penetr...

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Topics: Face shield (69%)

45 Citations


Open accessPosted Content
20 Apr 2020-
Abstract: Flow physics plays a key role in nearly every facet of the COVID-19 pandemic. This includes the generation and aerosolization of virus-laden respiratory droplets from a host, its airborne dispersion and deposition on surfaces, as well as the subsequent inhalation of these bioaerosols by unsuspecting recipients. Fluid dynamics is also key to preventative measures such as the use of face masks, hand-washing, ventilation of indoor environments, and even social distancing. This article summarizes what we know, and more importantly, what we need to learn about the science underlying these issues so that we are better prepared to tackle the next outbreak of COVID-19 or a similar disease.

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14 Citations


Open accessJournal ArticleDOI: 10.1080/02786826.2021.1933377
Abstract: Universal mask wearing is recommended to help control the spread of COVID-19. Masks reduce the expulsion of aerosols of respiratory fluids into the environment (called source control) and offer som...

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Topics: Airborne transmission (57%)

5 Citations


Open accessPosted Content
Willy Garcia1, Willy Garcia2, Baptiste Fray3, Alexandre Nicolas2  +1 moreInstitutions (3)
Abstract: This work aims to assess the risks of Covid-19 disease spread in diverse daily-life situations (referred to as scenarios) involving crowds of unmasked pedestrians, mostly outdoors. More concretely, we develop a method to infer the global number of new infections from patchy observations of pedestrians. The method relies on ad hoc spatially resolved models for disease transmission via virus-laden respiratory droplets, which are fit to existing exposure studies about Covid-19. The approach is applied to the detailed field data about pedestrian trajectories and orientations that we acquired during the pandemic. This allows us to rank the investigated scenarios by the transmission risks that they present; importantly, the obtained hierarchy of risks is conserved across all our transmission models (except the most pessimistic ones): Street cafes present the largest average rate of new infections caused by an attendant, followed by busy outdoor markets, and then metro and train stations, whereas the risks incurred while walking on fairly busy streets (average density around 0.1 person/m^2) are comparatively quite low. Models that assume isotropic transmission of the virus fail to reproduce these results. In scenarios with a moving crowd, we find that density is the main factor influencing the estimated infection rate. Finally, our study explores the efficiency of street and venue redesigns in mitigating the viral spread: While the benefits of enforcing one-way foot traffic in (wide) walkways are unclear, changing the geometry of queues substantially affects disease transmission risks.

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Topics: Crowds (51%)

5 Citations


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49 results found


Open accessJournal ArticleDOI: 10.1056/NEJMC2004973
Abstract: Aerosol and Surface Stability of SARS-CoV-2 In this research letter, investigators report on the stability of SARS-CoV-2 and SARS-CoV-1 under experimental conditions. The viability of the two virus...

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5,763 Citations


Open accessJournal ArticleDOI: 10.1001/JAMA.2020.2565
Yan Bai, Lingsheng Yao, Tao Wei, Fei Tian1  +3 moreInstitutions (2)
14 Apr 2020-JAMA
Abstract: This study describes possible transmission of novel coronavirus disease 2019 (COVID-19) from an asymptomatic Wuhan resident to 5 family members in Anyang, a Chinese city in the neighboring province of Hubei.

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Topics: Asymptomatic carrier (57%)

3,104 Citations


Open accessJournal ArticleDOI: 10.1016/S0140-6736(20)31142-9
Derek K. Chu1, Elie A. Akl1, Elie A. Akl2, Stephanie Duda1  +38 moreInstitutions (3)
27 Jun 2020-The Lancet
Abstract: Summary Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19 and is spread person-to-person through close contact. We aimed to investigate the effects of physical distance, face masks, and eye protection on virus transmission in health-care and non-health-care (eg, community) settings. Methods We did a systematic review and meta-analysis to investigate the optimum distance for avoiding person-to-person virus transmission and to assess the use of face masks and eye protection to prevent transmission of viruses. We obtained data for SARS-CoV-2 and the betacoronaviruses that cause severe acute respiratory syndrome, and Middle East respiratory syndrome from 21 standard WHO-specific and COVID-19-specific sources. We searched these data sources from database inception to May 3, 2020, with no restriction by language, for comparative studies and for contextual factors of acceptability, feasibility, resource use, and equity. We screened records, extracted data, and assessed risk of bias in duplicate. We did frequentist and Bayesian meta-analyses and random-effects meta-regressions. We rated the certainty of evidence according to Cochrane methods and the GRADE approach. This study is registered with PROSPERO, CRD42020177047. Findings Our search identified 172 observational studies across 16 countries and six continents, with no randomised controlled trials and 44 relevant comparative studies in health-care and non-health-care settings (n=25 697 patients). Transmission of viruses was lower with physical distancing of 1 m or more, compared with a distance of less than 1 m (n=10 736, pooled adjusted odds ratio [aOR] 0·18, 95% CI 0·09 to 0·38; risk difference [RD] −10·2%, 95% CI −11·5 to −7·5; moderate certainty); protection was increased as distance was lengthened (change in relative risk [RR] 2·02 per m; pinteraction=0·041; moderate certainty). Face mask use could result in a large reduction in risk of infection (n=2647; aOR 0·15, 95% CI 0·07 to 0·34, RD −14·3%, −15·9 to −10·7; low certainty), with stronger associations with N95 or similar respirators compared with disposable surgical masks or similar (eg, reusable 12–16-layer cotton masks; pinteraction=0·090; posterior probability >95%, low certainty). Eye protection also was associated with less infection (n=3713; aOR 0·22, 95% CI 0·12 to 0·39, RD −10·6%, 95% CI −12·5 to −7·7; low certainty). Unadjusted studies and subgroup and sensitivity analyses showed similar findings. Interpretation The findings of this systematic review and meta-analysis support physical distancing of 1 m or more and provide quantitative estimates for models and contact tracing to inform policy. Optimum use of face masks, respirators, and eye protection in public and health-care settings should be informed by these findings and contextual factors. Robust randomised trials are needed to better inform the evidence for these interventions, but this systematic appraisal of currently best available evidence might inform interim guidance. Funding World Health Organization.

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Topics: Absolute risk reduction (50%), Meta-analysis (50%)

1,869 Citations


Open accessJournal ArticleDOI: 10.1038/S41591-020-0843-2
03 Apr 2020-Nature Medicine
Abstract: We identified seasonal human coronaviruses, influenza viruses and rhinoviruses in exhaled breath and coughs of children and adults with acute respiratory illness. Surgical face masks significantly reduced detection of influenza virus RNA in respiratory droplets and coronavirus RNA in aerosols, with a trend toward reduced detection of coronavirus RNA in respiratory droplets. Our results indicate that surgical face masks could prevent transmission of human coronaviruses and influenza viruses from symptomatic individuals.

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Topics: Respiratory virus (62%), Coronavirus (61%), Orthomyxoviridae (56%) ... read more

1,236 Citations


Open accessJournal ArticleDOI: 10.1038/S41586-020-2271-3
Yuan Liu1, Zhi Ning2, Yu Chen1, Ming Guo1  +12 moreInstitutions (4)
27 Apr 2020-Nature
Abstract: The ongoing outbreak of coronavirus disease 2019 (COVID-19) has spread rapidly on a global scale. Although it is clear that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is transmitted through human respiratory droplets and direct contact, the potential for aerosol transmission is poorly understood1-3. Here we investigated the aerodynamic nature of SARS-CoV-2 by measuring viral RNA in aerosols in different areas of two Wuhan hospitals during the outbreak of COVID-19 in February and March 2020. The concentration of SARS-CoV-2 RNA in aerosols that was detected in isolation wards and ventilated patient rooms was very low, but it was higher in the toilet areas used by the patients. Levels of airborne SARS-CoV-2 RNA in the most public areas was undetectable, except in two areas that were prone to crowding; this increase was possibly due to individuals infected with SARS-CoV-2 in the crowd. We found that some medical staff areas initially had high concentrations of viral RNA with aerosol size distributions that showed peaks in the submicrometre and/or supermicrometre regions; however, these levels were reduced to undetectable levels after implementation of rigorous sanitization procedures. Although we have not established the infectivity of the virus detected in these hospital areas, we propose that SARS-CoV-2 may have the potential to be transmitted through aerosols. Our results indicate that room ventilation, open space, sanitization of protective apparel, and proper use and disinfection of toilet areas can effectively limit the concentration of SARS-CoV-2 RNA in aerosols. Future work should explore the infectivity of aerosolized virus.

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1,037 Citations