surgical masks and disease transmission

With the coronavirus spreading, I’ve seen authority figures advising that surgical masks worn by sick people can prevent them from spreading disease, but surgical masks worn by healthy people can’t prevent them from contracting disease.

So why are immune-compromised patients (e.g. people in the middle of chemo) often seen wearing surgical masks?

Presumably wearing a mask provides some non-zero level of protection for the wearer, but just how much? Have there been controlled studies assessing to what degree exposure is reduced for mask-wearers?


People required to wear masks for such medical reasons are instructed in the proper manner to put on, adjust, and remove such masks to actually get some utility out of them.

At work we have a couple customers who have been wearing masks for 1-2 years now for medical reasons. They wear the N95 masks that the medical people treating those with infectious diseases wear, and they wear them properly fitted and don’t touch them or fiddle with them or pull them down to talk to the person next to them. Touching/fiddling/pulling them down are all mistakes the untrained commonly make and which sort of make wearing masks pointless.

The only thing flimsy, loose “surgical masks” are good for are containing coughs and sneezes. Which is why when you see video of infected people being transported they’re often seen wearing them. It’s to protect other people around them more than to protect them.

Damn little unless you know what you’re doing and wear them properly.

Having had to wear various masks/respirators as part of past jobs, if you are wearing them correctly they aren’t entirely comfortable. They aren’t agony, either, but you do notice them, they do make it harder to communicate with others, they can get uncomfortable, itchy, sweaty, dirty… A lot of people have trouble putting up with all that, but if they can’t put up with even a little discomfort then wearing them is pointless. Even wasteful and selfish if there are others with greater need who can’t get them due to hoarding by others.


I’m aware that some of the research regarding masks is from the 1950’s, and is being stretched beyond it’s original validity. What is the quality of the edidence showing that untrained mask wearing is pointless ?

The current pandemic came up at a dinner party I attended over the weekend, and both of the physicians present admitted that masks were pretty much just for show even saying some surgeons they know would dispense with them if they could get away with it.

But that’s also why we have nurses. Because doctors are known to ignore basic infection control (including hand washing) if they aren’t watched.

In a traditional setting, doctors are outcome oriented, and nurses are process oriented. Doctors moderate the pointless and counter-productive processes, and nurses moderate the inclination of doctors to ignore processes that don’t seem to have an immediately recognizable outcome.

Here is one cite.

That link is hardly a cite on the ineffectiveness of masks. All it talks about is how putting on a mask improperly could increase the amount of particles getting through.

While I agree that surgical masks do little in viral infection protection, there was a study/article I remember reading that quantified the degree of protection masks could offer. Unfortunately, this was a long time ago and I don’t have a link or any numbers. However, the biggest caveat that stood out in my mind was that masks needed to be changed every 15-20 minutes because the moisture from exhalation nullified the protective ability of the mask. On top of that, the experiments were done in such a controlled fashion that its results couldn’t be applied to a real-world scenario where people are putting on masks incorrectly, or constantly touching their face or mask, and not washing their hands often enough. In fact, it mentioned regular hand washing as the most effective method of preventing viral and bacterial infection.

Considering how often I see people not wash their hands, I’m surprised there aren’t more sick people.

The notion that they don’t help is complete nonsense. I actually heard one Dr. say masks can’t possibly work because the virus can fit through the pores of the mask, which is so asinine as to beggar belief. The idea is to block the aerosolized saliva containing the virus. Doctors are discouraging mask use because they:

  1. Fear a shortage of masks for those who urgently need them
  2. Fear a panic from those who don’t get them
  3. Fear the mask will provide a false sense of security leading to the abandonment of other preventative measures. The general public also needs to be informed how to don, wear, remove, and dispose them.

These are all completely valid concerns, but what they are saying simply isn’t true. Having said that I’d take washing my hands and avoiding touching my face any day over a mask.

What’s so asinine about that? Even masks that are PFE/VFE rated, (which aren’t the ones most people are panic buying), will allow viruses smaller than 0.1 microns to pass through. No mask offers or claims 100% filtration efficiency.

It’s asinine because it completely misses the point. Yes, viruses could fit through, but they travel on aerosolized saliva droplets usually larger than .1 microns (97% are <1, but .1 is the outside figure). Saying they are a guarantee is obviously wrong but I’ve seen a few doctors quoted as saying they are ineffective, which is just as clearly not true.

If you could get the folks with the viral infections to wear them, they’d be great.

Huh. I’m sure you know more about the subject than I do, but it’s certainly not the statement of a lone “asinine” doctor. Here’s Timothy Brewer a professor of epidemiology and medicine at UCLA’s Fielding School of Public Health and its David Geffen School of Medicine:

I’m kind of thinking with those credentials, he’s not too likely to say asinine things about an epidemic virus.

In other words, Brewer is not affirming the view that “masks can’t possibly work because the virus can fit through the pores of the mask”. He’s saying that, if you are currently uninfected, masks will do little to stop you getting infected, but he’s affirming that they do work for minimising the spread of the infection from those who are infected, which is what they are supposed to do. If you’re infected or think you could be you should wear a mask, and it will make a material difference.


He is talking about the ear loop type of “surgical mask” that does not seal against one’s face. That’s what he means by not tight enough. I’d like to ask those doctors, if you were out in public and someone sneezed directly at your face, would you want to have a mask on, or no mask on?

I’m not saying everyone should be wearing them, but what’s being said about them in the US is disingenuous and inconsistent even with other developed countries.

Then I guess it’s a matter of how you want to define “effective”. Will it block viruses? No. Will it act as a barrier to saliva? Sure, but so would these.

You’d rather have the mask on, obvously. But someone sneezing directly into your face is probably not the transmission risk you most need to worry about.


This is another example for which I think that good evidence is perhaps missing. It is not proved to what extent COVID-19 is spread by droplet emission, and to what is extent it is spread by “lone virus” emission. If it’s spread by droplets from your nose, anything just has to block droplets. If your expired air contains virus particles, virions, from your deep lungs, then masks may not be effective.

I don’t think we know for sure the ratio of infections to causation method.
We can know that droplets directly in the face from a sneeze or cough would definitely do it, so we could look at it as like wearing a helmet when riding a bike; the chance of me falling off my bike today is remote, but the helmet is there if that should happen.

And while surgical mask < N95 mask < mask + enclosing glasses < hazmat suit, that doesn’t make it daft to wear a surgical mask. So it annoys me to hear people making sneering at people wearing surgical masks, especially when it’s the only option for many. (I’m not accusing you at all of this, UDS, just making a wider point).

I think the point is that surgical masks are of more value in limiting transmission by those who are already infected than they are in guarding against infection in those who aren’t.

By all means wear a surgical mask to guard against infection, if it gives you comfort. But understand that it offers relatively little protection, and that frequent washing of your hands with soap and hot water is likely to provide a far greater measure of protection than the mask can.