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Comment by octodog | Hacker News Reader

This is seriously and dangerously wrong information.

Surgical masks are particularly helpful in stopping _infected_ people from spreading the disease.

New information and data on asymptomatic spreaders means that the CDC (and many other Western health authorities) are considering changing their advice. The idea is that everyone must assume they are an asymptomatic spreader.

Additionally, surgical masks aren't the only PPE that medical workers use to protect themselves. Furthermore, hospitals and medical workers need surgical masks for many different non-coronavirus activities.

See here for more info:https://www.npr.org/sections/health-shots/2020/03/31/8245604...

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Unfortunately, I think you are on the wrong side of the science on this one.

First, you're implying that the data is new, but it's been around for a long time:

https://docs.google.com/document/d/1HLrm0pqBN_5bdyysOeoOBX4p...

> Surgical masks are particularly helpful in stopping _infected_ people from spreading the disease.

One of the ways the CDC twisted the information was to pretend this is only about surgical masks. There are also N95 masks, but the advice from the CDC and Surgeon General was generalized to all masks, not just surgical masks. Like this tweet:

    Seriously people- STOP BUYING MASKS!  

    They are NOT effective in preventing
    general public from catching #Coronavirus,
    but if healthcare providers can’t get
    them to care for sick patients, it puts
    them and our communities at risk!

Nothing in there distinguishes surgical from N95 masks, which really do block 95% of pathogens.

Furthermore, even surgical masks block 60-80% of pathogens. And if you seal the sides with tape, they block as much as other respirators.

And for the public, 60-80% is wayyyyy better than nothing!

So although it's true that there is a shortage of medical-grade masks for healthcare workers, and it's true that we should give them priority for any masks we have, it's absolutely a lie to say that "masks" in general are not effective at stopping the virus for the public.

No, what you just said is seriously wrong. The CDC even coauthored a paper that found during the SARS-1 outbreak that among contacts of known cases, those untrained people that regularly wore surgical masks had a 70% reduced risk of contracting SARS. 60% for those that wore them intermittently. And in fact, research suggests that masks are actually MORE protective for the people wearing them.

Note the following points, with sources (The context is a bit off because I did this research in response to another question, but the points are still pretty much relevant here):

1. Regular old surgical masks (not N95 respirators), when worn by the public without training, had a strong protective effect for the people wearing them during the SARS-CoV-1 outbreak. They reduced the risk of infection by ~70%. (Source: https://wwwnc.cdc.gov/eid/article/10/2/03-0730_article)

2. Despite being very different in their ability to actually filter out fine particles, N95 respirators and surgical masks actually show no significant difference in their ability to prevent diagnosed respiratory infections including influenza, when worn by healthcare workers according to two large meta-studies. Though both had a protective effect over no mask. (Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4868605/) (2nd source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5779801/)

3. Improvised, homemade masks have only a marginally lower filtration efficiency than surgical masks (which we established are about as effective as an N95 respirator anyway). (Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2440799/) (2nd source: https://www.researchgate.net/publication/258525804_Testing_t...)

4. There is evidence in the studies linked in item 2 that hand hygiene alone did not demonstrate much of a protective effect (for civilians caring for a sick family member) against transmission of influenza compared to use of any type of mask.

5. When infected people wear a mask, it helps reduce the amount of viral shedding which occurs, presumably making them less likely to infect others. (Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3591312/)

From your study on point 2: "Results of our systematic review and meta-analysis show that there was no significant difference between N95 respirators and surgical masks when used by health care workers to prevent transmission of acute respiratory infections from patients. However, wide 95% CIs from our meta-analysis must be interpreted as insufficient evidence to determine whether there is a clinically significant difference."

What the study says is that we don't have enough information. As an example, one of the studies referenced in that study gives odds of 0.58 for getting infected with surgical and 0.42 with N95.

Bonus quote: "Furthermore, we do not have an adequate understanding of the number, size and dispersion of the droplets that contain live, infectious particles produced by infected patients.56 A laboratory-based study reported data that humans infected with influenza rarely produce aerosols that contain infectious viral particles.57 In 2 other laboratory studies, participants infected with influenza produced droplets containing viral RNA, but viral RNA could not be detected on manikin headforms or on filters of breathing manikins at distances as close as 0.1 m following participants breathing, counting, coughing or laughing.7"

I don't understand your point.

The quote you're referring to, regarding 95% CIs, in context specifically applies to comparing surgical masks vs. N95 respirators, not mask vs. no-mask. In other words, surgical masks are not shown to be worse than N95 respirators.

That's in complete agreement with the point 2 that you're apparently trying to refute.

Except they didn't specify surgical masks as opposed to N95.

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