Does wearing a mask prevent one from getting swine flu?

The answer: Yes and no and the jury is still out.

Mexico City is full of people wearing small, gauze or paper facemasks.  I saw plenty of drivers in cars, a few bicyclists, most of the waiters at the local taquerías, and even a guy going for a run all wearing a blue or white tapaboca (literally “covers mouth”).  So I thought it would be a good idea to figure out if they actually do any good.  Here’s the results of a brief foray into medical science:


The hypothesis: It seemed to me that, in most situations, wearing a mask doesn’t help… after all, flu germs are viruses and way too small to be stopped by a gauze mask.  (In reality, you’d need a very special filter to completely stop them.)  Masks do stop big droplets in the air, such as those you exhale when you sneeze.  However, by being big, these droplets tend to fall out of the air very quickly, so there isn’t much for a mask to stop when you inhale.  On the other hand, masks do stop droplets from sneezes when you exhale, so it might be very helpful for a sick person to wear one; surgeons wears masks to reduce their risks of contaminating a patient.  

The method: I did some checking by first googling “does wearing a mask prevent you from getting the flu”.  There are a ton of answers out there, most of which are on those sometimes useful “wiki-type answer” blogs.  However, in this case, I found a lot of smart-ass answers like “only if you wear it” and “more than not wearing one.”  Wow, talk about a waste of e-space.   

But there is a real answer: Since I’m the type of doctor that reads journal articles, I next decided to go straight to the source: I searched for recent scholarly publications on face masks and the flu.  What I found is that there have been few scientific studies on whether wearing a mask helps (to be specific, one).  Researchers have found that a person is 80% less likely to catch the flu from a sick (and, presumably snotty) child in their own home if they wear a mask.  But the researchers aren’t sure why.  It may be that, by wearing a mask, a person is less likely to touch their own face with their hands (or their child’s), thus preventing the spread of flu by physical contact, and that it has very little to do with breathing in germs.

2008 Article: CITE: The First Randomized, Controlled Clinical Trial of Mask Use in Households to Prevent Respiratory Virus Transmission, MacIntyre et al., International Journal of Infectious Diseases, Volume 12, Supplement 1, December 2008, Page e328 — LINK: Science Direct (a pay site – grrr!), or find a nice summary on the Imperial College of London’s website.

The conclusion: The latest scientific studies show that masks help reduce the chances of getting the flu from someone in your own home but they do not suggest that the benefits of wearing a mask extend outdoors, or are better that being good about washing your hands.  If, indeed, it turns out that wearing a mask helps because it prevents a person from touching their face, the smartass comments could be wrong.  In fact, it might be better if you took your mask and put it on your sick child.  

Of course, we all might be better off if people just washed their hands more.  (An informal survey at ITAM finds that there are a lot of Mexican college-age males who need to learn this.)


México, D.F.



The conclusion, part 2: I’m not sure which is more annoying, the useless and smart-ass wikis, the accountants at science direct, or the undergrads at ITAM who don’t wash their hands.


2 Responses

  1. […]  Perhaps one of the most ubiquitous changes are the presence of the ever-popular face masks.  I’m still convinced that they don’t do very much, but if they keep people from rubbing their faces and (hopefully […]

  2. […] to criticize the initiative, but I had some significant reservations about the practice (such as here and here).  Why?  Simply put, I don’t believe the benefit outweighs the costs.  Not only […]

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