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No matter which of those two mask types are employed, a relevant May 2020 meta-study on pandemic influenza published by the CDC found that face masks had no eff

No matter which of those two mask types are employed, a relevant May 2020 meta-study on pandemic influenza published by the CDC found that face masks had no effect, neither as personal protective equipment nor as a source control. "In pooled analysis, we found no significant reduction in influenza transmission with the use of face masks". "Disposable medical masks (also known as surgical masks) are loose-fitting devices that were designed to be worn by medical personnel to protect accidental contamination of patient wounds, and to protect the wearer against splashes or sprays of bodily fluids (36). 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. Our systematic review found no significant effect of face masks on transmission of laboratory-confirmed influenza." "Proper use of face masks is essential because improper use might increase the risk for transmission." Has the CDC analysis been refuted? https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article

dragonwriter 6y ago
> May 2020 meta-study on pandemic influenza That's probably quite important if you are trying to control pandemic influenza, but SARS-COV-2 isn't influenza. Different pathogens have different characteristics, and thus different responses to protective measures. AFAIK, most influenzas are much more prone to airborne transmission than SARS-COV-2, where the main concern is droplet transmission (though some airborne transmission seems to occur), against which masks that are ineffective against airborne transmission can be quite effective. You wouldn't judge the value of condoms in preventing the spread of AIDS by studies of how effective they were in preventing the spread of the flu, either.
- EB-Barrington 6y ago
  What size particle/droplet is most important in stopping Covid transmission?
jcheng 6y ago
https://www.cdc.gov/coronavirus/2019-ncov/more/masking-science-sars-cov2.html https://www.cdc.gov/coronavirus/2019-ncov/more/masking-scien... https://www.nature.com/articles/d41586-020-02801-8 https://www.nature.com/articles/d41586-020-02801-8
aeturnum 6y ago
As I said, I'm a layman, but several things jump out to me. The first thing I think of is that the meta-study you linked is for influenza. Obviously covid and influenza are similar but I think there are important differences (we did not, for instance, have as many cases of influenza in any of the last fifty years as we have of covid this year). In particular, I know that the asymptomatic transmission of covid is unusual and is not something that happens in influenza[0]. The studies that support mask wearing in my link are on mask mandates (though there are also case studies that suggest masks have been effective). I believe that mandating masks reduces transmission of the virus and I don't think it's necessary to reconcile that fact with the fact that masks don't reduce the spread of influenza. The version of the study you linked is formatted oddly and the tables are on another page. A pdf of their article is easier to read, I think [3]. From Table 2 (and the discussion around it) I take that they are hoping to catalog open questions and are not seeking to make a recommendation about proper procedure. Therefore I think it's perfectly in keeping with Jingyi Xiao, et. al. to recommend wearing masks based on the covid-specific studies while recognizing we have no evidence that masks prevent influenza. [0] While you can transmit influenza when you're not showing symptoms, my understanding is that covid is different enough that we shouldn't compare them. That could be wrong and if you have anything to contribute I'd be interested to see it. [1] https://www.healthaffairs.org/doi/10.1377/hlthaff.2020.00818 https://www.healthaffairs.org/doi/10.1377/hlthaff.2020.00818 [2] https://www.researchgate.net/publication/342198360_Association_of_country-wide_coronavirus_mortality_with_demographics_testing_lockdowns_and_public_wearing_of_masks_Update_June_15_2020 https://www.researchgate.net/publication/342198360_Associati...

dragonwriter 6y ago

> May 2020 meta-study on pandemic influenza That's probably quite important if you are trying to control pandemic influenza, but SARS-COV-2 isn't influenza. Different pathogens have different characteristics, and thus different responses to protective measures. AFAIK, most influenzas are much more prone to airborne transmission than SARS-COV-2, where the main concern is droplet transmission (though some airborne transmission seems to occur), against which masks that are ineffective against airborne transmission can be quite effective. You wouldn't judge the value of condoms in preventing the spread of AIDS by studies of how effective they were in preventing the spread of the flu, either.

EB-Barrington 6y ago
What size particle/droplet is most important in stopping Covid transmission?

jcheng 6y ago

https://www.cdc.gov/coronavirus/2019-ncov/more/masking-science-sars-cov2.html https://www.cdc.gov/coronavirus/2019-ncov/more/masking-scien... https://www.nature.com/articles/d41586-020-02801-8 https://www.nature.com/articles/d41586-020-02801-8

aeturnum 6y ago

As I said, I'm a layman, but several things jump out to me. The first thing I think of is that the meta-study you linked is for influenza. Obviously covid and influenza are similar but I think there are important differences (we did not, for instance, have as many cases of influenza in any of the last fifty years as we have of covid this year). In particular, I know that the asymptomatic transmission of covid is unusual and is not something that happens in influenza[0]. The studies that support mask wearing in my link are on mask mandates (though there are also case studies that suggest masks have been effective). I believe that mandating masks reduces transmission of the virus and I don't think it's necessary to reconcile that fact with the fact that masks don't reduce the spread of influenza. The version of the study you linked is formatted oddly and the tables are on another page. A pdf of their article is easier to read, I think [3]. From Table 2 (and the discussion around it) I take that they are hoping to catalog open questions and are not seeking to make a recommendation about proper procedure. Therefore I think it's perfectly in keeping with Jingyi Xiao, et. al. to recommend wearing masks based on the covid-specific studies while recognizing we have no evidence that masks prevent influenza. [0] While you can transmit influenza when you're not showing symptoms, my understanding is that covid is different enough that we shouldn't compare them. That could be wrong and if you have anything to contribute I'd be interested to see it. [1] https://www.healthaffairs.org/doi/10.1377/hlthaff.2020.00818 https://www.healthaffairs.org/doi/10.1377/hlthaff.2020.00818 [2] https://www.researchgate.net/publication/342198360_Association_of_country-wide_coronavirus_mortality_with_demographics_testing_lockdowns_and_public_wearing_of_masks_Update_June_15_2020 https://www.researchgate.net/publication/342198360_Associati...