I even heard an "expert" saying on national TV that non-professional masks were worse, because the virus could actually stick to it :S

They recommend against wearing medical to help cull the shortage, and they recommend against wearing non-medical because they can provide a false sense of security, especially when worn incorrectly. Both very good reasons, IMO.

I just assume that anyone wearing a mask is doing so because they're infected, as per the recommendations, and I'm giving them a wide berth.

Maybe a minority, as there will always be, but I think most people are aware of the difference between medical and non-medical masks, and feel the messaging is consistent.

If mask use becomes mandatory, will there still be groups of people standing in the middle of supermarket shouting to each other? Sure, just like there are now. The difference is those people will at least have masks on.

Another reason to wear a mask.

I think I'm helping more by going with the recommendations and not wearing a mask. Some people feel better wearing them, and that's fine too.

Further, just yesterday on HN, there was a post about how a University study of airplane travelers showed mask-wearers got both benefits - they rarely caught anything and rarely infected anyone, even with the simplest masks.

Do you have a source for this? It's contrary to most of what I've read (droplets through air is primary vector).

"In an adjusted analysis of compliant subjects, masks as a group had protective efficacy in excess of 80% against clinical influenza-like illness." -https://www.ijidonline.com/article/S1201-9712(08)01008-4/ful...

All the folks saying masks don't work literally never cite to any actual study - I think it's something like 90+ studies showing masks work and maybe 1 or 2 without a good result for masks.

> Droplets through the air is not primary vector

and

> hand to nose mouth contact is THE primary vector for this illness

In contrast, Johns Hopkins guide currently states: "Transmission - By respiratory droplets and by fomite. Virus found in respiratory secretions and saliva. - Viral shedding by asymptomatic people described, uncertain to what degree this occurs and abets transmission. - Stool shedding also described, but uncertain what role, if any, that plays." https://www.hopkinsguides.com/hopkins/view/Johns_Hopkins_ABX...

In daily living you touch door handles, gas pump handles, elevator buttons, railings, subway hang straps and bars etc. Even before covid, how many people sneezed on you? Far fewer.

If we just were worried about folks sneezing on us we could stop washing our hands.

Here's the best article I've found on transmission, and a key excerpt. http://www.cidrap.umn.edu/news-perspective/2020/03/commentar...

> In risk communication guidelines for healthcare, however, the WHO states, "COVID-19 appears to spread most easily through close contact with an infected person. When someone who has COVID-19 coughs or sneezes, small droplets are released and, if you are too close, you can breathe in the virus" (emphasis added).9 But wait: Inhalation is not part of the traditional definition of droplet transmission.

> For healthcare organizations, the CDC recommends airborne, in addition to standard (contact) and droplet precautions, for the care of COVID-19 suspected or confirmed patients.10

> For the general public, the CDC describes SARS-CoV-2 transmission as primarily by droplets from coughs or sneezes, which "land in the mouths or noses of people who are nearby or possibly inhaled into the lungs" (emphasis added).11 But, again, inhalation is a new addition to the traditional definition of droplets. In contrast to its recommendations for healthcare, the CDC makes no mention of airborne transmission in public settings.

> The CDC admits some possibility that COVID-19 may be transferred by hands to mouth, nose, or eyes from contaminated surfaces, but notes that "this is not thought to be the main way the virus spreads."11

It's hyper local. I got lucky and hit Costco in December. Feel like I still see it in stores sometime, but people need to shop around.

Acetaminophen is trickier now.

Also, don’t forget that in medical facilities N95 masks are fitted specifically to individuals. You can’t just throw one on and be protected. Most people won’t go through the trouble of doing that properly. At that point it’s like putting your shirt over your nose: looks like you are protected but there are giant gaps that let in air.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3373043/

A cut t-shirt over your nose is actually quite good, so long as the pattern is somewhat tested. No, its no where close to an N95 mask, but even aerosol sprays can be somewhat mitigated with a simple cut t-shirt.

There are some internet studies suggesting an efficacy of 70% for T-shirts against 1-micron (bacteria) and 0.02 micron (viruses) particles. That's 6x worse than an N95 mask, but much better than unprotected.

EDIT: It seems like the flu (also a 0.02 micron virus) is primarily on water-droplets 5 microns in size. So we don't actually have to reach N95 mask levels for a major amount of protection, aiming at the 5 micron sized moisture bubbles is already going to help us severely.

Your argument about trapping virus inside the mask is not very convincing. If you are putting a physical barrier between your respiratory system and air in high-risk areas (general stores, pharmacies and public transportation), then statistically there should be far more prevented contacts with viruses than trapped virus particles.

The incorrectly fitted masks should provide some benefit over no mask, so this doesn't seem as a good argument for not wearing masks. I would think that even putting shirt over nose gives some protection as it prevents touching face and diminishes odds of contamination with spit particles. Besides, the article is about home-made masks and not N95 masks.

The only convincing reason against masks is that they give false sense of security, so they shouldn't be the _only_ measure. Washing hands, wearing masks and physical distancing can only be beneficial.

Where is that evidence?

"in medical facilities N95 masks are fitted specifically to individuals. You can't just throw one on and be protected. Most people won't go through the trouble of doing that properly."

Most people haven't been washing their hands properly either, and yet the government has gone to great lengths to educate people on how to properly wash their hands. There's no reason they couldn't do the same with mask fitting.

Lets not over-dramaticize N95 masks. An N95 mask is just 95% effective. Its not N99 or N100.

N95 is the relatively cheap and disposable mask. Its "custom fit seal" is the little metal bar that you push down on your nose.

Here is 3M's official fitting video. Its actually not very hard to use: https://www.youtube.com/watch?v=05wyH1-mLGk

Then elastic bands shove the mask against your face, forming an airtight seal. This can be effectively replicated with a decent hand-made mask solution (although the filtration of a hand-made DIY mask is much much worse, and completely untested compared to N95 designs)

Given the fact that we're in an N95 mask shortage situation, I think DIY home-made masks are the only solution for the general public. It just takes some scissors and a T-Shirt to make.

Even if it only reduces R0 by a few procent that would mean a lot?

So, they're recommending we don't use masks, so that more masks are available for medical professionals, so that when most of us get sick via community transmission (because we don't have masks), the medical professionals can also run out of masks while they treat us.