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Assessment of the risks of viral transmission in non-confined crowds
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TLDR
In scenarios with a moving crowd, it is found that density is the main factor influencing the estimated infection rate, and the efficiency of street and venue redesigns in mitigating the viral spread is explored.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.read more
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References
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Report 9: Impact of non-pharmaceutical interventions (NPIs) to reduce COVID19 mortality and healthcare demand
Neil M. Ferguson,Daniel J Laydon,G Nedjati Gilani,Natsuko Imai,Kylie E. C. Ainslie,Marc Baguelin,Sangeeta N. Bhatia,A Boonyasiri,Z Cucunuba Perez,Gina Cuomo-Dannenburg,Amy Dighe,Ilaria Dorigatti,Han Fu,Katy A. M. Gaythorpe,W Green,Arran Hamlet,Wes Hinsley,Lucy C Okell,S Van Elsland,H Thompson,Robert Verity,Erik M. Volz,Haowei Wang,Y Wang,Patrick G T Walker,Caroline E. Walters,Peter Winskill,Charles Whittaker,Christl A. Donnelly,Steven Riley,Azra C. Ghani +30 more
TL;DR: Neil M Ferguson, Daniel Laydon, Gemma Nedjati-Gilani, Natsuko Imai, Kylie Ainslie, Sangeeta Bhatia, Adhiratha Boonyasiri, Zulma Cucunubá, Gina Cuomo-Dannenburg, Amy Dighe, Ilaria Dorigatti, Han Fu, Katy Gaythorpe, Will Green, Arran Hamlet, Wes Hinsley, Lucy C Okell.
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Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis.
Derek K. Chu,Elie A. Akl,Elie A. Akl,Stephanie Duda,Karla Solo,Sally Yaacoub,Holger J. Schünemann,Holger J. Schünemann,Amena El-Harakeh,Antonio Bognanni,Tamara Lotfi,Mark Loeb,Anisa Hajizadeh,Anna Bak,Ariel Izcovich,Carlos A. Cuello-Garcia,Chen Chen,David Harris,Ewa Borowiack,Fatimah Chamseddine,Finn Schünemann,Gian Paolo Morgano,Giovanna E.U. Muti Schünemann,Guang Chen,Hong Zhao,Ignacio Neumann,Jeffrey Chan,Joanne Khabsa,Layal Hneiny,Leila Harrison,Maureen A. Smith,Nesrine Rizk,Paolo Giorgi Rossi,Pierre AbiHanna,Rayane El-Khoury,Rosa Stalteri,Tejan Baldeh,Thomas Piggott,Yuan Zhang,Zahra Saad,Assem M. Khamis,Marge Reinap +41 more
TL;DR: The optimum distance for avoiding person-to-person virus transmission is investigated and the use of face masks and eye protection to prevent transmission of viruses is assessed to investigate the effects of physical distance, face masks, and eye Protection on virus transmission in health-care and non-health-care settings.
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Quantifying SARS-CoV-2 transmission suggests epidemic control with digital contact tracing.
Luca Ferretti,Chris Wymant,Michelle Kendall,Lele Zhao,Anel Nurtay,Lucie Abeler-Dörner,Michael Parker,David Bonsall,Christophe Fraser +8 more
TL;DR: A mathematical model for infectiousness was developed to estimate the basic reproductive number R0 and to quantify the contribution of different transmission routes and the requirements for successful contact tracing, and the combination of two key parameters needed to reduce R0 to less than 1 was determined.
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Respiratory virus shedding in exhaled breath and efficacy of face masks.
Nancy H. L. Leung,Daniel K.W. Chu,Eunice Y.C. Shiu,Kwok-Hung Chan,James J. McDevitt,Benien J.P. Hau,Benien J.P. Hau,Hui-Ling Yen,Yuguo Li,Dennis K. M. Ip,J. S. Malik Peiris,WH Seto,WH Seto,Gabriel M. Leung,Donald K. Milton,Benjamin J. Cowling +15 more
TL;DR: A study of 246 individuals with seasonal respiratory virus infections randomized to wear or not wear a surgical face mask showed that masks can significantly reduce detection of coronavirus and influenza virus in exhaled breath and may help interrupt virus transmission.
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Commentary on Ferguson, et al., "Impact of Non-pharmaceutical Interventions (NPIs) to Reduce COVID-19 Mortality and Healthcare Demand".
Stephen Eubank,I. Eckstrand,Bryan Lewis,Srinivasan Venkatramanan,Madhav V. Marathe,Christopher L. Barrett +5 more
TL;DR: A coarse taxonomy of models is discussed and the context and significance of the Imperial College and other models in contributing to the analysis of COVID-19 are explored.
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