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The studies you cite focus on the use of masks to protect the wearer of the mask. The purpose of masks is not to protect the wearer of the mask but to protect o

by yodon 6y ago

The studies you cite focus on the use of masks to protect the wearer of the mask. The purpose of masks is not to protect the wearer of the mask but to protect others. In simple hand-waving terms the mask diffuses the wearer's exhalation reducing the velocity of the air stream and its contained particles, thereby reducing the distance the particles can travel and increasing the odds that the particles drop out of the airstream and onto a surface before they encounter another person. The diffusive effects of masks does not provide a 100% barrier but given that Covid-19 appears to be predominantly transmitted via airborne particles rather than surface contact, mask wearing can still have a large impact on transmission without being directly protective of the wearer.

blisseyGo 6y ago
No, the first study I cited states: > There is limited evidence for their effectiveness in preventing influenza virus transmission either when worn by the infected person for source control or when worn by uninfected persons to reduce exposure. And the later study states non-N95 masks allow 97%.
- yodon 6y ago
  The Xiao, et al study you refer to is a historical literature review of transmission of prior non-Covid-19 viruses. It is unclear if the historical studies involved social distancing or close proximity (critical to current understanding of Covid-19 mask efficacy) and it is concerning that the paper reports "most studies were underpowered because of sample size and some studies also reported suboptimal adherence in the face mask group." More importantly, Covid-19 appears to have different transmission characteristics than other influenza style viruses, making literature reviews such as the one you cite less predictive of Covid-19 behaviors than would often have been the case with other viruses. The paper is interesting but it's definitely not supported by their data to say the paper shows masks worn by infected individuals are ineffective at reducing the spread of Covid-19 in a social distance context. [edit: updated with additional detail from the cited paper]

by yodon 6y ago

blisseyGo 6y ago

No, the first study I cited states: > There is limited evidence for their effectiveness in preventing influenza virus transmission either when worn by the infected person for source control or when worn by uninfected persons to reduce exposure. And the later study states non-N95 masks allow 97%.

yodon 6y ago
The Xiao, et al study you refer to is a historical literature review of transmission of prior non-Covid-19 viruses. It is unclear if the historical studies involved social distancing or close proximity (critical to current understanding of Covid-19 mask efficacy) and it is concerning that the paper reports "most studies were underpowered because of sample size and some studies also reported suboptimal adherence in the face mask group." More importantly, Covid-19 appears to have different transmission characteristics than other influenza style viruses, making literature reviews such as the one you cite less predictive of Covid-19 behaviors than would often have been the case with other viruses. The paper is interesting but it's definitely not supported by their data to say the paper shows masks worn by infected individuals are ineffective at reducing the spread of Covid-19 in a social distance context. [edit: updated with additional detail from the cited paper]