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Date: June 25, 2020 02:03AM
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31142-9/fulltext"The findings of this systematic review of 172 studies (44 comparative studies; n=25 697 patients) on COVID-19, SARS, and MERS provide the best available evidence that current policies of at least 1 m physical distancing are associated with a large reduction in infection, and distances of 2 m might be more effective. These data also suggest that wearing face masks protects people (both health-care workers and the general public) against infection by these coronaviruses, and that eye protection could confer additional benefit. However, none of these interventions afforded complete protection from infection, and their optimum role might need risk assessment and several contextual considerations. No randomised trials were identified for these interventions in COVID-19, SARS, or MERS."
"The use of face masks was protective for both health-care workers and people in the community exposed to infection, with both the frequentist and Bayesian analyses lending support to face mask use irrespective of setting. Our unadjusted analyses might, at first impression, suggest use of face masks in the community setting to be less effective than in the health-care setting, but after accounting for differential N95 respirator use between health-care and non-health-care settings, we did not detect any striking differences in effectiveness of face mask use between settings."
https://www.researchgate.net/publication/340603522_Face_Masks_Against_COVID-19_An_Evidence_Review"The preponderance of evidence indicates that mask wearing reduces the transmissibility per contact by reducing transmission of infected droplets in both laboratory and clinical contexts. Public mask wearing is most effective at stopping spread of the virus when compliance is high. The decreased transmissibility could substantially reduce the death toll and economic impact while the cost of the intervention is low. Thus we recommend the adoption of public cloth mask wearing, as an effective form of source control, in conjunction with existing hygiene, distancing, and contact tracing strategies. We recommend that public officials and governments strongly encourage the use of widespread face masks in public, including the use of appropriate regulation."
https://www.reuters.com/article/us-health-coronavirus-masks-study/widespread-mask-wearing-could-prevent-covid-19-second-waves-study-shows-idUSKBN23G37V"Population-wide face mask use could push COVID-19 transmission down to controllable levels for national epidemics, and could prevent further waves of the pandemic disease when combined with lockdowns, according to a British study on Wednesday.
The research, led by scientists at the Britain’s Cambridge and Greenwich Universities, suggests lockdowns alone will not stop the resurgence of the new SARS-CoV-2 coronavirus, but that even homemade masks can dramatically reduce transmission rates if enough people wear them in public.
The study found that if people wear masks whenever they are in public it is twice as effective at reducing the R value than if masks are only worn after symptoms appear.
In all scenarios the study looked at, routine face mask use by 50% or more of the population reduced COVID-19 spread to an R of less than 1.0, flattening future disease waves and allowing for less stringent lockdowns"
https://www.acpjournals.org/doi/10.7326/M20-2567"Physical distancing, hand hygiene, and disinfection of surfaces are the cornerstones of infection control during the coronavirus disease 2019 (COVID-19) pandemic. At the same time, governments, international agencies, policymakers, and public health officials have been debating the validity of recommending use of nonmedical masks by the general public to reduce the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We believe that these decisions should be informed by evidence. Although no direct evidence indicates that cloth masks are effective in reducing transmission of SARS-CoV-2, the evidence that they reduce contamination of air and surfaces is convincing and should suffice to inform policy decisions on their use in this pandemic pending further research.
Cloth does not stop isolated virions. However, most virus transmission occurs via larger particles in secretions, whether aerosol (<5 µm) or droplets (>5 µm), which are generated directly by speaking, eating, coughing, and sneezing; aerosols are also created when water evaporates from smaller droplets, which become aerosol-sized droplet nuclei. The point is not that some particles can penetrate but that some particles are stopped, particularly in the outward direction. Every virus-laden particle retained in a mask is not available to hang in the air as an aerosol or fall to a surface to be later picked up by touch.
When we apply the principles of evidence-based medicine to public policy, there is high-quality, consistent evidence that many (but not all) cloth masks reduce droplet and aerosol transmission and may be effective in reducing contamination of the environment by any virus, including SARS-CoV-2. No direct evidence indicates that public mask wearing protects either the wearer or others. Given the severity of this pandemic and the difficulty of control, we suggest that the possible benefit of a modest reduction in transmission likely outweighs the possibility of harm."