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Our local Pediatrician's office and General Practitioner's office both have a policy of giving a disposable face mask to each patient or visitor who has a noticeable cough or runny nose, and insist that it be worn before proceeding with check-in.

These surgical-style disposable face masks were also "popular" during outbreaks of respiratory illnesses over the past decade, including SARS, "Swine Flu" (H1N1), and "Bird Flu" (H3N8).

Is there any evidence to support or discount the effectiveness of disposable face masks in the spread of disease?

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    As a point of reference, being that I work at a company that makes a massive amount of respirators... a surgical style respirator may prevent the spread of infection from someone who's infected. Wearing those types to prevent breathing in airborne microbes is useless, though. You need true particulate respirators that seal against one's face for that. Surgical masks are just a barrier between your orifices and the outside. Filtration respirators (N/P 95 Niosh standards) will prevent breathing in things above their lower particle threshold.
    – Hendy
    Jul 29, 2011 at 22:01
  • I don’t understand. Wearing the mask can block the passage of airborne microbes from someone’s mouth or nose to outside their mask (to other people). But it doesn’t work in the reverse direction? Why are said microbes blocked in the first direction but not in the opposite direction.
    – froimovi
    Jan 26, 2021 at 1:24
  • To the well-credentialed individual above (the credential being that they work at a company that makes massive—not few, but massive—amounts of respirators): how exactly does the mask function as an effective barrier in one direction of airflow, but not for the reverse direction (more precisely, is “completely useless” for the latter direction).?
    – froimovi
    Feb 24, 2021 at 12:19
  • Depends if you ask this before or after the pandemic (when the entire western medical convention regarding those masks changed arbitrarily over night....and then everyone pretended it didn’t change)
    – froimovi
    Apr 9, 2021 at 15:42

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The best answer I can find is here: http://www.ncbi.nlm.nih.gov/pubmed/17828691 By clicking on the link, you should find several other supporting studies.

However, for those not inclined to click on the link above, I'll give a brief: 10 students out of 953 were found to be carrying S. aureus. All developed the common cold. The study looked at S. aureus dispersal for street clothes vs scrubs vs scrubs and gown vs scrubs, gown and mask. The study found that the mask had minimal effect on dispersal of S. aureus when compared to scrubs or scrubs and gown alone.

In short(from the study), the mask itself doesn't do much. If the GP had been really concerned, they would have had sick patients dress in clean surgical scrubs.

My guess is that the GP is looking for a "halo" effect. Boost the esteem of those waiting in queue with a common mark (mask) and get some reduction in aerosol germ spread.

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  • "get some reduction in aerosol germ spread." - this seems like a fairly efficient redactor of transmissions considering that aerosol and mucus are the main vectors of transmission for viruses like that according to my GP. The study seems to be of medical personnell, NOT patients - for the latter, wearing of scrubs is less important as they don't walk all around the hospital and interact with large amounts of people/furniture etc... Also, it's 100% unclear if it was the scrubs that had the effect, or merely changing from "sneezed-on" contaminated cloths.
    – user5341
    Jul 30, 2011 at 12:44
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First, it needs to be understood as per @Hendy's comment that disposable face masks can trap or allow airborne particles to pass through.

There are several studies to back this up and indicates that up to 100% of the particles could pass through:

That being said there are studies that confirm the benefits of wearing a face mask and the maths speaks for itself, even a 10% improvement is better than no protection at all right?

There are two studies worth mentioning this study:

We observed significant reductions in ILI during weeks 4-6 in the mask and hand hygiene group, compared with the control group, ranging from 35% (confidence interval [CI], 9%-53%) to 51% (CI, 13%-73%), after adjusting for vaccination and other covariates.

Face mask use alone showed a similar reduction in ILI compared with the control group, but adjusted estimates were not statistically significant. Neither face mask use and hand hygiene nor face mask use alone was associated with a significant reduction in the rate of ILI cumulatively.

And this study:

Influenza transmission was not reduced by interventions to promote hand washing and face mask use. This may be attributable to transmission that occurred before the intervention, poor facemask compliance, little difference in hand-washing frequency between study groups, and shared sleeping arrangements. A prospective study design and a careful analysis of sociocultural factors could improve future NPI studies.

There are a number of studies which conclude there is a positive benefits to wearing a face mask.

I would suggest from the information out there and from the above information that face masks could provide some benefit (reduced risk), however this would depend on the environment. A high amount of particles can be trapped or flow through the mask and if the wearer is in an environment where they are touching the same surfaces or breathing the same air for an extended period of time then the benefit could be negligible.

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There are different kinds of face mask, which are more or less effective.

During the SARS "crisis," I remember people complaining that the masks being made available weren't the effective (sub-micron, well-fitting) kind.

For example, Medical Face Mask Standards and Regulations says,

Surgical and procedure masks are effective against droplet transmission.

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