scholarly journals Aerosol transport measurements and assessment of risk from infectious aerosols: a case study of two German cash-and-carry hardware/DIY stores

2021 ◽  
Author(s):  
eberhard Bodenschatz ◽  
Gholamhossein Bagheri ◽  
Bardia Hejazi ◽  
Birte Thiede ◽  
Oliver Schlenczek
Keyword(s):  
Upper Bound ◽  
Disease Transmission ◽  
Face Mask ◽  
Indoor Environments ◽  
Aerosol Dynamics ◽  
Direct Exposure ◽  
Decay Times ◽  
Dominant Feature ◽  
Aerosol Dispersion ◽  
Cash And Carry

We report experimental results on aerosol dispersion in two large German cash-and-carry hardware/DIY stores to better understand the factors contributing to disease transmission by infectious human aerosols in large indoor environments. We examined the transport of aerosols similar in size to human respiratory aerosols (0.3μm-10μm) in representative locations, such as high-traffic areas and restrooms. In restrooms, the observed decay of aerosol concentrations was consistent with well-mixed air exchange. In all other locations, fast decay times were measured, which were found to be independent of aerosol size (typically a few minutes). From this, we conclude that in the main retail areas, including at checkouts, rapid turbulent mixing and advection is the dominant feature in aerosol dynamics. With this, the upper bound of risk for airborne disease transmission to a susceptible is determined by direct exposure to the exhalation cloud of an infectious. For the example of the SARS-CoV-2 virus, we find when speaking without a face mask and aerosol sizes up to an exhalation (wet) diameter of 50μm, a distance of 1.5me to be unsafe. However, at the smallest distance between an infectious and a susceptible, while wearing typical surgical masks and for all sizes of exhaled aerosol, the upper bound of infection risk is only ∼ 5% and decreases further by a factor of 100 (∼ 0.05%) for typical FFP2 masks for a duration of 20 min. This upper bound is very conservative and we expect the actual risk for typical encounters to be much lower. The risks found here are comparable to what might be expected in calm outdoor weather.

scholarly journals An upper bound on one-to-one exposure to infectious human respiratory particles

2021 ◽  
Vol 118 (49) ◽  
pp. e2110117118
Author(s):  
Gholamhossein Bagheri ◽  
Birte Thiede ◽  
Bardia Hejazi ◽  
Oliver Schlenczek ◽  
Eberhard Bodenschatz
Keyword(s):  
Upper Bound ◽  
Disease Transmission ◽  
Human Subjects ◽  
Face Mask ◽  
Ample Evidence ◽  
Infectious Dose ◽  
Social Distancing ◽  
Ambient Particle ◽  
One To One ◽  
Airborne Disease

There is ample evidence that masking and social distancing are effective in reducing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission. However, due to the complexity of airborne disease transmission, it is difficult to quantify their effectiveness, especially in the case of one-to-one exposure. Here, we introduce the concept of an upper bound for one-to-one exposure to infectious human respiratory particles and apply it to SARS-CoV-2. To calculate exposure and infection risk, we use a comprehensive database on respiratory particle size distribution; exhalation flow physics; leakage from face masks of various types and fits measured on human subjects; consideration of ambient particle shrinkage due to evaporation; and rehydration, inhalability, and deposition in the susceptible airways. We find, for a typical SARS-CoV-2 viral load and infectious dose, that social distancing alone, even at 3.0 m between two speaking individuals, leads to an upper bound of 90% for risk of infection after a few minutes. If only the susceptible wears a face mask with infectious speaking at a distance of 1.5 m, the upper bound drops very significantly; that is, with a surgical mask, the upper bound reaches 90% after 30 min, and, with an FFP2 mask, it remains at about 20% even after 1 h. When both wear a surgical mask, while the infectious is speaking, the very conservative upper bound remains below 30% after 1 h, but, when both wear a well-fitting FFP2 mask, it is 0.4%. We conclude that wearing appropriate masks in the community provides excellent protection for others and oneself, and makes social distancing less important.

scholarly journals Inflight Transmission of COVID-19 Based on Experimental Aerosol Dispersion Data

2021 ◽  
Author(s):  
Zhaozhi Wang ◽  
Edwin R Galea ◽  
Angus Grandison ◽  
John Ewer ◽  
Fuchen Jia
Keyword(s):  
High Efficiency ◽  
Face Mask ◽  
Generation Rate ◽  
Aviation Industry ◽  
Filtration System ◽  
Dispersion Data ◽  
Low Probability ◽  
Meal Service ◽  
Low Efficiency ◽  
Aerosol Dispersion

Abstract Background An issue of concern to the travelling public is the possibility of in-flight transmission of COVID-19 during long- and short-haul flights. The aviation industry maintains that the probability of contracting the illness is small based on reported cases, modelling and data from aerosol dispersion experiments conducted on-board aircraft. Methods Using experimentally derived aerosol dispersion data for a B777–200 aircraft and a modified version of the Wells-Riley equation we estimate inflight infection probability for a range of scenarios involving quanta generation rate and face mask efficiency. Quanta generation rates were selected based on COVID-19 events reported in the literature while mask efficiency was determined from the aerosol dispersion experiments. Results The MID-AFT cabin exhibits the highest infection probability. The calculated maximum individual infection probability (without masks) for a 2-hour flight in this section varies from 4.5% for the ‘Mild Scenario’ to 60.2% for the ‘Severe Scenario’ although the corresponding average infection probability varies from 0.1% to 2.5%. For a 12-hour flight, the corresponding maximum individual infection probability varies from 24.1% to 99.6% and the average infection probability varies from 0.8% to 10.8%. If all passengers wear face masks throughout the 12-hour flight, the average infection probability can be reduced by approximately 73%/32% for high/low efficiency masks. If face masks are worn by all passengers except during a one-hour meal service, the average infection probability is increased by 59%/8% compared to the situation where the mask is not removed. Conclusions This analysis has demonstrated that while there is a significant reduction in aerosol concentration due to the nature of the cabin ventilation and filtration system, this does not necessarily mean that there is a low probability or risk of in-flight infection. However, mask wearing, particularly high-efficiency ones, significantly reduces this risk.

scholarly journals The prevalence and clinical significance of Presymptomatic COVID-19 patients: how we can be one step ahead in mitigating a deadly pandemic

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Juen Kiem Tan ◽  
Dalleen Leong ◽  
Hemalatha Munusamy ◽  
Nor Hazwani Zenol Ariffin ◽  
Najma Kori ◽  
...  
Keyword(s):  
Clinical Significance ◽  
Disease Transmission ◽  
Temporal Dynamics ◽  
Face Mask ◽  
Chi Square ◽  
Exact Test ◽  
Atypical Symptoms ◽  
One Step ◽  
Receive Treatment ◽  
Transmission Studies

Abstract Background Presymptomatic COVID-19 patients have been identified as a major stumbling block in efforts to break the chain of transmission. Studies on temporal dynamics of its shedding suggests it peaks 1–2 days prior to any symptom onset. Therefore, a large proportion of patients are actively spreading the disease unknowingly whilst undetected. However, lengthy lockdowns and isolation leads to a host of socioeconomic issues and are impractical. Conversely, there exists no study describing this group and their clinical significance despite their key role in disease transmission. Methods As a result, we devised a retrospective study to look at the prevalence of presymptomatic patients with COVID-19 from data sourced via our medical records office. Subsequently, we identify early indicators of infection through demographic information, biochemical and radiological abnormalities which would allow early diagnosis and isolation. In addition, we will look into the clinical significance of this group and their outcome; if it differs from asymptomatic or symptomatic patients. Descriptive statistics were used in addition to tabulating the variables and corresponding values for reference. Variables are compared between the presymptomatic group and others via Chi-square testing and Fisher’s exact test, accepting a p value of < 0.05 as significant. Results Our analysis shows a higher proportion of presymptomatic patients with atypical symptoms like chest pain while symptomatic patients commonly present with respiratory symptoms like cough and shortness of breath. Besides that, there were more females presenting as presymptomatic patients compared to males (p = 0.019) and these group of patients were likely to receive treatment (p < 0.001). Otherwise, we were not able to identify other statistically significant markers suggesting a patient is presymptomatic. Conclusion As we have little means of identifying these silent spreaders, it highlights further the importance of general measures implemented to stop COVID-19 transmission like social distancing, face mask, and widespread testing.

scholarly journals Retail store customer flow and COVID-19 transmission

2021 ◽  
Vol 118 (11) ◽  
pp. e2019225118
Author(s):  
Robert A. Shumsky ◽  
Laurens Debo ◽  
Rebecca M. Lebeaux ◽  
Quang P. Nguyen ◽  
Anne G. Hoen
Keyword(s):  
Disease Transmission ◽  
Dominant Mode ◽  
Direct Transmission ◽  
Throughput Rate ◽  
Full Compliance ◽  
Population Prevalence ◽  
Direct Exposure ◽  
Close Proximity ◽  
Mode Of Transmission ◽  
Models Of Disease

We examine how operational changes in customer flows in retail stores affect the rate of COVID-19 transmission. We combine a model of customer movement with two models of disease transmission: direct exposure when two customers are in close proximity and wake exposure when one customer is in the airflow behind another customer. We find that the effectiveness of some operational interventions is sensitive to the primary mode of transmission. Restricting customer flow to one-way movement is highly effective if direct exposure is the dominant mode of transmission. In particular, the rate of direct transmission under full compliance with one-way movement is less than one-third the rate under two-way movement. Directing customers to follow one-way flow, however, is not effective if wake exposure dominates. We find that two other interventions—reducing the speed variance of customers and throughput control—can be effective whether direct or wake transmission is dominant. We also examine the trade-off between customer throughput and the risk of infection to customers, and we show how the optimal throughput rate drops rapidly as the population prevalence rises.

scholarly journals The mask dilemma: unmasking the myths and facts

2020 ◽  
Vol 8 (1) ◽  
pp. 453
Author(s):  
Varsha Narayanan
Keyword(s):  
Health Care ◽  
Economic Burden ◽  
Disease Transmission ◽  
Scientific Evidence ◽  
Face Mask ◽  
Mass Vaccination ◽  
Morbidity And Mortality ◽  
Public Places ◽  
The People ◽  
Practical Guidelines

Coronavirus 2019 (COVID-19) has been spreading across the globe in 2020 with most countries being affected significantly in terms of the number of infected cases, morbidity and mortality, as well as health care and economic burden. Currently the most important individual and community measures for curtailing disease transmission are social distancing, hand sanitization and wearing of masks in public. It is important to advocate wearing masks in an effective and balanced manner and dispense supportive scientific evidence as well as practical guidelines and information in the community. Till the event of mass vaccination for COVID being available, improving the awareness, compliance and acceptance of the people towards proper wearing of a face mask when in public places, can be the most effective way for several countries to control transmission of COVID. 

scholarly journals Year of the face mask: do`s and don’ts during exercise

2020 ◽  
Vol 32 (1) ◽  
pp. 1-2
Author(s):  
Dina Christina Janse Van Rensburg ◽  
Lervasen Pillay ◽  
Sharief Hendricks ◽  
Jessica Hamuy Blanco
Keyword(s):  
Disease Transmission ◽  
Scientific Evidence ◽  
Sports Participation ◽  
Face Mask ◽  
Public Spaces ◽  
Short Report ◽  
Informed Decisions ◽  
The Face

The COVID-19 pandemic causes widespread anxiety and uncertainty regarding disease transmission. In many countries people are obliged to wear a face mask in public spaces. Individuals involved in sports participation at any level need to make informed decisions on wearing a face mask during exercise. Currently there is no scientific evidence on what to advise regarding the safety of wearing a face mask during exercise, or what type of mask to use. This short report aims to answer these questions in a structured and practical way.

scholarly journals Knowledge and attitude toward coronavirus disease 19 pandemic among Saudi Arabia population: A cross-sectional study

2021 ◽  
Vol 9 ◽  
pp. 205031212110524
Author(s):  
Talal Shaikhain ◽  
Faisal Al-Husayni ◽  
Ghufran Bukhari ◽  
Bushra Alhawsa ◽  
Nora Shalabi ◽  
...  
Keyword(s):  
Saudi Arabia ◽  
Disease Transmission ◽  
Information Needs ◽  
Normal Population ◽  
Demographic Data ◽  
Face Mask ◽  
Cross Sectional Study ◽  
Sectional Study ◽  
Online Questionnaire ◽  
Cross Sectional

Background: Coronavirus disease 19 is a pandemic affecting millions worldwide. Since February 2020, new cases are reported in Saudi Arabia, and regulations have been imposed to control the spread of the disease and raise awareness. This study aimed to assess the knowledge and attitudes of the Kingdom’s residents toward coronavirus disease 19 during the early stages of the pandemic. Method: A cross-sectional study of 2071 participants who were recruited from various cities in Saudi Arabia. An online questionnaire was shared through social media, which contained questions about demographic data, general knowledge of coronavirus disease 19, and participants’ attitudes. Results: The mean age of the study population was 34 ± 12.4 years. Most of the participants agreed that coronavirus disease 19 is a pandemic and is more serious than seasonal influenza. More than 90% believed that handwashing and social distancing are effective in preventing disease transmission. No significant results were observed when comparing the knowledge of high-risk participants and the normal population. More than half of the cohort were strictly compliant with curfew regulations, handwashing, and face mask. Around 80% of the population is following coronavirus disease 19 news and information through official authorities’ press releases. Conclusion: The Kingdom of Saudi Arabia residents showed decent knowledge of coronavirus disease 19. Nevertheless, some information needs emphasizing and proper education. Frequent communication between healthcare authorities and the public is highly recommended.

scholarly journals The Prevalence and Clinical Significance of Presymptomatic COVID-19 Patients: How We Can be One Step Ahead in Mitigating a Deadly Pandemic

2020 ◽  
Author(s):  
Juen Kiem Tan ◽  
Dalleen Leong ◽  
Hemalatha Munusamy ◽  
Nor Hazwani Zenol Ariffin ◽  
Najma Kori ◽  
...  
Keyword(s):  
Clinical Significance ◽  
Disease Transmission ◽  
Respiratory Symptoms ◽  
Temporal Dynamics ◽  
Face Mask ◽  
Shortness Of Breath ◽  
Demographic Information ◽  
Atypical Symptoms ◽  
One Step ◽  
Transmission Studies

Abstract Presymptomatic COVID-19 patients have been identified as a major stumbling block in efforts to break the chain of transmission. Studies on temporal dynamics of its shedding suggests it peaks 1-2 days prior to any symptom onset. Therefore, a large proportion of patients are actively spreading the disease unknowingly whilst undetected. However, lengthy lockdowns and isolation leads to a host of socioeconomic issues and are impractical. Conversely, there exists no study describing this group and their clinical significance despite their key role in disease transmission. As a result, we devised a study to look at the prevalence of presymptomatic patients with COVID-19 and subsequently, identify early indicators of infection through demographic information, biochemical and radiological abnormalities which would allow early diagnosis and isolation. In addition, we will look into the clinical significance of this group and their outcome; if it differs from asymptomatic or symptomatic patients. Our analysis shows a higher proportion of presymptomatic patients with atypical symptoms like chest pain while symptomatic patients commonly present with respiratory symptoms like cough and shortness of breath. Besides that, there were more females presenting as presymptomatic patients and receiving treatment compared to males and this was found to be statistically significant. Otherwise, we were not able to identify other statistically significant markers suggesting a patient is presymptomatic. As we have little means of identifying these silent spreaders, it highlights further the importance of general measures implemented to stop COVID-19 transmission like social distancing, face mask, and widespread testing.

Face mask detection application and dataset

2021 ◽  
Vol 27 (2) ◽  
Author(s):  
Daniel Matthias ◽  
Chidozie Managwu ◽  
O. Olumide
Keyword(s):  
Disease Transmission ◽  
Face Mask ◽  
World Health ◽  
The World ◽  
The Face ◽  
Monitoring And Enforcement ◽  
Health Organization ◽  
Experimental Findings ◽  
Recognition Software ◽  
Deep Learning Model

The COVID–19 pandemic is, without any doubt, changing our world in ways that are beyond our wildest imagination. In a bid to curb the spiraling negative fallouts from the virus that has resulted in a large number of casualties and security concerns. The World Health Organization, amongst other safety protocols, recommended the compulsory wearing of face masks by individuals in public spaces. The problem with the enforcement of this and other relevant safety protocols, all over the world, is the reluctance and outright refusal of citizens to comply and the inability of relevant agencies to monitor and enforce compliance. This paper explores the development of a CCTV–enabled facial mask recognition software that will facilitate the monitoring and enforcement of this protocol. Such models can be particularly useful for security purposes in checking if the disease transmission is being kept in check. A constructive research methodology was adopted, where a pre-trained deep convolutionary neural network (CNN) (mostly eyes and forehead regions) used and the most probable limit (MPL) was use for the classification process. The designed method uses two datasets to train in order to detect key facial features and apply a decision-making algorithm. Experimental findings on the Real-World-Masked-Face-Dataset indicate high success in recognition. A proof of concept as well as a development base are provided towards reducing the spread of COVID-19 by allowing people to validate the face mask via their webcam. We recommend that the use of the app and to further investigate the development of highly robust detectors by training a deep learning model with respect to specified face-feature categories or to correctly and incorrectly wear mask categories.

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