Information about (simple) mask wearing (concerning covid19) is a complete mystery to me. On several official places it is not recommended for a person without symptoms to wear a mask. For example:

https://youtu.be/Ded_AxFfJoQ (time 0:20)

or here:


However no explanation is given - which makes me wonder (and even angry). I think everybody should wear a mask because:

  • Many persons feel ashamed wearing it, even those with symptoms. If everybody wears it, they do not feel ashamed and wear it.

  • As far as I know, one is (wrt covid19) contagious before developing symptoms. So if everybody wears the mask also these people do.

The two above points act as a collective protection.

  • Simple mask certainly will lower "getting / spreading illness" probability. Of course the "holes" (in a simple mask) are too big to prevent completely virus to enter (or get out when coughing), but it lowers probability! Even if it lowers the transmission probability by e.g. 5%, it might be a lot. As a hypothetical example: it might reduce R0 from 1.02 to 0.97 and so stop the virus spread so fast.

The videos are full of self-contradiction. In the same video


time 0:50 the lady says I should wear a mask if I am in contact with an infected person... why if it is inefficient?

Question: What are reasons for not recommending wearing a mask?

  • I am not a medical professional, thus only providing a comment. There is not enough masks available, so they recommend that let the medical service people have them. Most countries do not manufacture masks anymore (low tech, low profit). The #1 manufacturing country is China, they need it themselves in these days, very minimum export in the past two months. I am talking about surgical masks and lower levels. N95 is another story.
    – Nobody
    Commented Mar 23, 2020 at 14:02
  • Then rather say "do not wear it" they should say "wear something", e.g. scarf, home-made mask. But good point.
    – F. Jatpil
    Commented Mar 23, 2020 at 14:11
  • I just found this news report by New York Times.
    – Nobody
    Commented Mar 23, 2020 at 14:38
  • @F.Jatpil In countries like Czech Republic and Slovakia wearing something (scarf, home-made masks) is now obligatory. People are making home made masks and donating to other people or even to hospitals. The epidemiologists in charge in these countries consider it an important factor to lower the number of infected people from every infected individual. Every lowering of R0 counts even if the protection of one individual is not big.. Commented Mar 23, 2020 at 17:33
  • I've seen pictures of people with "home made masks" which continuously fall off their faces. Or, even if they aren't slipping off, the majority of non-trained individuals will habitually touch the mask or mess with it in some way, bringing their hands to their faces. I feel like it's mostly to avoid people doing dumb crap like this to try and prevent the disease, when all they end up doing is making things worse. Commented Apr 5, 2020 at 13:52

1 Answer 1


TL;DR: please WEAR A MASK!

(unless your nearby hospitals are out of it, in which case give your masks to them and stay at home)

The link you mentioned provides the reason that the CDC likely has in mind (though I agree it doesn't identify it clearly as the reason):

The worldwide supply of masks is limited. It's critical that we use them appropriately. [i.e., prioritizing them for high-risk people].

Thought the CDC is now considering recommending general public wear face coverings in public.

{1} compiled different government guidelines on the use of mask. You'll see that some of them do recommend wearing a mask whereas others such as the UK mentions that "there is very little evidence of widespread benefit for members of the public". Some governments such as the South Korean government even distribute free respiratory masks (2 KF94 per person per week in South Korea).

A great summary on the use of fask masks from Stanford researcher Michael Lin, PhD-MD:

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  • {1} Feng, Shuo, Chen Shen, Nan Xia, Wei Song, Mengzhen Fan, and Benjamin J. Cowling. "Rational use of face masks in the COVID-19 pandemic." The Lancet Respiratory Medicine (2020). https://doi.org/10.1016/S2213-2600(20)30134-X
  • Comments are not for extended discussion; this conversation has been moved to chat.
    – Carey Gregory
    Commented Mar 31, 2020 at 13:52

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