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> Just like they are about the masks for covid-19

What is the CDC saying about masks for covid-19? Are you saying they're not effective or the CDC is downplaying their effectiveness?




CDC plain saying they are not effective and not recommending them


Wrong. It's much more nuanced than that.

Surgical masks are not effective at preventing infection. They are effective at spreading infection.

New data on asymptomatic spreaders means than public health authorities are considering changing their advice. The default assumption would then be that everyone has it, and should therefore wear a mask to prevent spreading it.


>Surgical masks are not effective at preventing infection. They are effective at spreading infection.

This is a common misconception, for which CDC is also partially the one to be blamed.

Laboratory tests find that improvised cloth masks block 60 – 80% of virus particles

Most experts in the early 2000s agreed that these masks were probably better than nothing.

https://bmjopen.bmj.com/content/bmjopen/5/4/e006577.full.pdf

https://www.cambridge.org/core/services/aop-cambridge-core/c...

http://akkie.mods.jp/2019-nCoV/images/c/c0/%E3%82%B5%E3%83%B...


> Laboratory tests find that improvised cloth masks block 60 – 80% of virus particles

How many virus particles do you need to become infected? Is 20% of the load in a typical aerosol droplet from an asymptomatic infected person above or below that critical number?


https://www.thelancet.com/journals/laninf/article/PIIS1473-3...

>higher viral loads associated with severe clinical outcomes


It's a numbers game. There is a certain probability that each virion can spur and infection, so the less you get the better. If virions had a 100% infection chance then sure, but it's much lower than that.


>Surgical masks are not effective at preventing infection.

Actually, they very much are.

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) The CDC even coauthored this one.

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. When infected people wear a mask, it does help 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/)

In fact, if you dig into the research evaluating different mask types including homemade masks, one of them suggests that the masks are actually MORE protective on the way in than they are in preventing shedding of aerosols: (Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2440799/) (2nd source: https://www.researchgate.net/publication/258525804_Testing_t...)


Weeks ago the CDC lied, saying that masks aren't effective and that the general public shouldn't wear them. They did this ostensibly to keep the existing mask supply available only to medical workers. Needless to say, if they're ineffective for the general public, they're ineffective for doctors and nurses. And so people saw through the bullshit


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...


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.


I remember reading the CDC website, and I don't remember them saying that.

Their Jan 8 publication says:

> CDC currently recommends a cautious approach to symptomatic patients with a history of travel to Wuhan City. Such patients should be asked to wear a surgical mask as soon as they are identified and be evaluated in a private room with the door closed. Personnel entering the room to evaluate the patient should use contact precautions and wear an N95 disposable facepiece respirator

- https://emergency.cdc.gov/han/HAN00424.asp

And on Feb 21 their FAQ said:

> Q: Does CDC recommend the use of facemask in the community to prevent COVID-19?

> A: CDC does not recommend that people who are well wear a facemask to protect themselves from respiratory illnesses, including COVID-19. You should only wear a mask if a healthcare professional recommends it. A facemask should be used by people who have COVID-19 and are showing symptoms. This is to protect others from the risk of getting infected. The use of facemasks also is crucial for health workers and other people who are taking care of someone infected with COVID-19 in close settings (at home or in a health care facility).

- https://wayback.archive-it.org/13529/20200221195555/https://...

So I'm not seeing where they ever said they were not effective. It says that if you are sick or showing symptoms you should wear a mask, but that they don't advise the general public to wear a mask because they are crucial to health care workers. To me this sounds like very good advice.


Right but if you can't tell if you're infected then you should always wear a mask. I mean how much more additional trouble is that then making everyone stay home.


That there wasn't enough masks?

To be clear, I'm just saying the CDC never lied. You can disagree with its recommendation to try and save the masks supplies for Health Workers and people showing symptoms, but it never said that masks are ineffective. If anything, it might have said that it's still unclear how effective they are, but even then, it clearly took the cautionary approach.

If you read to the contrary, that was probably just a poor news source spewing misinformation. Or at least, I cannot find where on the official CDC channels they would have lied.


> Needless to say, if they're ineffective for the general public, they're ineffective for doctors and nurses.

This isn't necessarily true. Doctors and nurses could have training on how to use masks, whereas most people will touch their faces more with them on.


Not sure why this is getting downvoted. Wearing a mask correctly, in a way that gets a proper seal, is something health care pros are trained to do and most people aren’t. If you’re constantly touching the mask (which has been concentrating particles in the air) and then touching other parts of your face, the mask is less effective.


When you know touching your face is the worst thing you can do this has personally been a proven lie. I assume if there is science behind a study that tracks people through out the day and shows people touch their face more often, that they were not told to avoid touching their face. I think to touch an eye brow or my hair and my face subtly moves and I feel the mask on my face and realize that I should not come anywhere close to my face. People are not stupid, they just need to be educated.




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