Fact: Medical facemasks are not effective at reducing the spread of viruses.
Source (From the CDC): https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article
This study, published by the CDC in May of this year, outlines over seven decades worth of real-world, empirical data on the effectiveness of facemasks and handwashing against viral spread. This study finds that there is some evidence that handwashing is effective at reducing viral spread but there is no significant evidence that facemasks reduce viral spread. This study is specific to influenza, but can be reasonably extrapolated to COVID-19 as approximately 20-50% of influenza viruses are coronaviruses depending on the year and region.
Excerpts from the study:
“In our systematic review, we identified 10 RCTs that reported estimates of the effectiveness of face masks in reducing laboratory-confirmed influenza virus infections in the community from literature published during 1946–July 27, 2018. In pooled analysis, we found no significant reduction in influenza transmission with the use of face masks (RR 0.78, 95% CI 0.51–1.20; I<sup>2</sup> = 30%, p = 0.25)”
“We did not find evidence that surgical-type face masks are effective in reducing laboratory-confirmed influenza transmission, either when worn by infected persons (source control) or by persons in the general community to reduce their susceptibility”
I suggest that people save a digital copy of this study on their computers in addition to printing physical copies of it. I anticipate that the study could be removed from the internet as its exposure increases.