Quote:
Originally Posted by blueash
Is this simple enough? Even a stable genius can understand.
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Gee that's really scientific!
DR Fauci on if masks really work
"Masks Don't Work" Dr Fauci tells the truth about masks | #debunkthisfauci - YouTube
Two Doctors and experts in respiratory diseases review the science at CIDRAP
We do, however, have data from laboratory studies that indicate cloth masks or face coverings offer very low filter collection efficiency for the smaller inhalable particles we believe are largely responsible for transmission, particularly from pre- or asymptomatic individuals who are not coughing or sneezing.
The guidelines from the Centers for Disease Control and Prevention (CDC) for face coverings initially did not have any citations for studies of cloth material efficiency or fit, but some references have been added since the guidelines were first posted. We reviewed these and found that many employ very crude, non-standardized methods (Anfinrud 2020, Davies 2013, Konda 2020, Aydin 2020, Ma 2020) or are not relevant to cloth face coverings because they evaluate respirators or surgical masks (Leung 2020, Johnson 2009, Green 2012).
We are concerned that many people do not understand the very limited degree of protection a cloth mask or face covering likely offers as source control for people located nearby.
Cloth masks and face coverings likely do not offer the same degree of protection as physical distancing, isolation, or limiting personal contact time.
Will face coverings 'flatten the curve' and stop the pandemic?
We have reviewed the many modeling studies that purport to demonstrate that cloth masks or face coverings have the potential for flattening the curve or significantly decrease the number of cases. These studies fail to recognize several important facts:
The filter performance of a cloth material does not directly translate or represent its performance on an individual, because it neglects the understanding of fit.
Cloth masks or coverings come in a variety of shapes, sizes, and materials and are not made according to any standards.
Transmission is not simply a function of short random interactions between individuals, but rather a function of particle concentration in the air and the time exposed to that concentration.
A cloth mask or face covering does very little to prevent the emission or inhalation of small particles. As discussed in an earlier CIDRAP commentary and more recently by Morawska and Milton (2020) in an open letter to WHO signed by 239 scientists, inhalation of small infectious particles is not only biologically plausible, but the epidemiology supports it as an important mode of transmission for SARS-CoV-2, the virus that causes COVID-19.
COMMENTARY: Masks-for-all for COVID-19 not based on sound data | CIDRAP