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Comment by deelowe | Hacker News Reader

What's more frustrating is the exact same logic applies to "social distancing." Social distancing will not completely stop people from getting sick. It'll just slow the spread. So, according to the CDC, an imperfect solution for quarantine is totally fine, but when it comes to masks, only n95 or better are worth pursuing.

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It's quite likely that in all the scenarios a mask may have a useful effect, N95 or better is the only time it works.

For medical professionals in close contact with patients and dealing with airborne-protocol pathogens (which is what a droplet-mediated pathogens like SARS2 becomes classed as once patients are coughing and being intubated) then a bad mask is quite probably worse then no mask (this has precedent: ineffective masks obstruct breathing, which makes you take deeper breaths and draw more particles in deeper in your lungs - it's a big problem when dealing with fine dusts in construction).

It's highly likely that even basic surgical masks have some impact. A fit-tested N95 is the gold standard, but the widespread use of surgical masks in Asia during the SARS epidemic does seem to have had an impact.

https://wwwnc.cdc.gov/eid/article/10/2/03-0730_article

> It’s quite likely that in all the scenarios a mask may have a useful effect, N95 or better is the only time it works.

You’re saying you think anything less than an N95 has 0 effectiveness. Why do you believe this is likely? Are you aware of the data that says otherwise?

https://news.ycombinator.com/item?id=22655436

https://www.researchgate.net/publication/258525804_Testing_t...

N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial

https://jamanetwork.com/journals/jama/fullarticle/2749214

“As worn by health care personnel in this trial, use of N95 respirators, compared with medical masks, in the outpatient setting resulted in no significant difference in the rates of laboratory-confirmed influenza.”

To be clear, this trail was for outpatient care — not necessarily applicable to shoving tubes down throats, but probably applicable to people walking down the street.

That quote is saying that N95 masks are no better than medical masks, not that medical masks have 0 effectiveness.

The data from the Davies paper is not very convincing. The home made solutions offered significantly less protection and and had major problems with fit. Even their conclusions were — it’s better than nothing, but not a proper substitute.

> However, these masks would provide the wearers little protection from microorgan- isms from others persons who are infected with respiratory diseases. As a result, we would not recommend the use of homemade face masks as a method of reducing transmission of infection from aerosols.

Better than nothing is the whole point. N95 masks are not a substitute for avoiding exposure in the first place, but nobody’s saying N95 masks are ineffective because of that fact.

The recommendation here is assuming you have access to something better. If you have no access to something better, a homemade mask is better than no mask at all, until you can get something better. As others have pointed out here, it’s rather odd to suggest we should scoff at this imperfect solution, when there are no perfect solutions short of 100% full and complete quarantine, which is completely unrealistic.

This is about Influenza but I doubt it’s that different from Corona: https://pubmed.ncbi.nlm.nih.gov/20497389/

Are you a doctor? Can you explain why a study about influenza would apply to SARS-CoV-2? Or is your doubt baseless speculation?

SARS-CoV-2 is a spheroid with a diameter of about 120 nm.

There's a lot of variation in influenza viruses, but most are spheroids or ellipsoids with a diameter from 80-120 mm.

For simple mechanical filtering, such as with a mask, they are going to behave pretty similar.

The CDC does not say that only n95 or better are worth pursuing

https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/f...

Agree & upvoted; this needs to be better understood. Especially noteworthy is the section you linked to is written for health-care workers, and they’re confirming that a homemade mask is better than nothing (while also recommending the homemade mask dead last.)

Unfortuately, the CDC really is giving out conflicting guidance here. For example, higher up in the section for lay-people is this: “You do not need to wear a facemask unless you are caring for someone who is sick (and they are not able to wear a facemask). Facemasks may be in short supply and they should be saved for caregivers.” https://www.cdc.gov/coronavirus/2019-ncov/prepare/prevention... (In “How to Prepare | Protect Yourself”)

I don't see a contradiction. The CDC is trying to maximize public health benefit. They recommend stronger protection for people with more exposure to higher levels of the virus. Coincidentally, the people with higher levels of exposure also happen to be health care workers, who need the best available protection to save lives

If you are not exposed to high levels and are not required to put yourself at risk to care for patients, you are at low risk. You can protect yourself with milder measures like social distancing and face protection that is not as effective but not in such short supply

Maybe I misread your intent. I thought you were mostly pointing out the section titled “When No Facemasks Are Available, Options Include”, which would mean we’re talking about something that is not in short supply. I thought you were pointing out that, among other things, the CDC is saying that home-made masks are better than nothing, even for health care professionals, and even if it’s a last resort.

I mean I agree, of course, that they’re trying to maximize public health benefit, I just don’t think the guidance is at all clear to the public. The idea that anything less than N95 is useless is pervasive, you can see it right here on HN. My parents and co-workers believe it because it’s been reported in the mass media in the last weeks: “the CDC said masks don’t protect you!”.

For people who need to work or shop in public places, any kind of masks at all might well be statistically significant alternatives for people who are unable to practice social distancing. China seems to be doing it effectively right now; people are required to wear masks to go to work. They’re not telling the public to avoid masks because doctors need them, they’re telling the public not to leave the house and not to enter a work building without something over your face. It seems like the CDC is saying the opposite, you should not wear a mask unless you’re a doctor. If a bandana is even 50% or 30% or even 5% effective, and they want to maximize public health benefit, why aren’t they recommending people start with what they have at home for times when public exposure is necessary? Seems like that would both increase public health and deflect demand for surgical masks & N95 masks at the same time, no?

That's not necessary so. While "not doing social distancing right" will not increase your risk compared to not trying, with masks it's not so clear cut: You have to touch your face to put them on and take them off, and people might touch their face more often to adjust them etc. That increases the risk, at least if you wear them to protect yourself. And people might take greater risks because they feel safe. If this is not counterbalanced by the risk reduction through wearing a mask, it's a problem. Additionally, if there is a mask shortage, it might increase the risk indirectly, even for those who don't want to spread it.

> So, according to the CDC … only n95 or better are worth pursuing.

Current CDC guidance is “facemasks are an acceptable alternative when the supply chain of respirators cannot meet the demand”.¹

¹ https://www.cdc.gov/coronavirus/2019-ncov/infection-control/...

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