Surgical masks prevent infection

Saturday, March 14th, 2020

Thomas Talhelm, Associate Professor of Behavior Science at the University of Chicago Booth School of Business, founded Smart Air, “a social enterprise to help people in China breathe clean air without shelling out thousands of dollars for expensive purifiers,” and he decided to look at N95 masks versus surgical masks:

Scientists tested this question by randomly assigning over 2,000 nurses to wear N95 or surgical masks. Then they tracked how many of them caught the flu.


Differences weren’t significant, although surgical mask users actually had slightly lower infection rates.


Researchers in Canada randomly assigned 446 nurses to wear N95 or surgical masks during a few months of cold and flu seasons (September to December). Then they tracked how many got the flu or a cold.

Again, no significant difference! Both masks performed just as well at preventing the transmission of the viruses. Twenty percent of nurses wearing surgical masks got sick versus 22% wearing N95 masks.


Researchers in Australia studied parents taking care of their children, who were sick with the flu.


In raw percentages, 17% of all participants got sick versus 5% among surgical masks and 4% wearing N95 masks.


Bottom line: There’s scientific evidence finding that (1) masks prevent flu infection and (2) surgical masks prevent infection of viruses like the coronavirus (Covid-19), as well as more sophisticated N95 masks.


  1. Kirk says:

    I’ve always wondered about the real source for the masks working… Obviously, the cloth ain’t filtering particles as you breathe, but… I would lay money that the real reason they work is because they keep people from putting their booger hooks near their mouth.

    Which is why the surgical masks work as well as the N95 ones. It ain’t the filtering, it’s the prevention of finger-banging your mouth-hole.

  2. Joe says:

    Masks may be filtering aerosols

  3. Paul from Canada says:

    I think you are probably right, but some of it will be the filtering effect also.

    Now the current Corona virus seems to be airborne in and of itself, but most airborne diseases are associated with sneezed or coughed aerosol droplets, and it the mask keeps you from actually breathing them in/ingesting them (i.e. by getting caught in the mask).

    Much the same way hand washing and other hygiene methods don’t eliminate all of the infectious material, just reduces the total amount of it to the point where your body can deal with this smaller virus or bacterial load.

    Also, it probably acts as a subconscious signal that the wearer is sick, and people keep a slightly greater distance, but overall, I think you are right. If it is in your mouth and or other mucous membranes, and you can’t touch your mouth, you won’t get it on your hands,and thus won’t put it on the doorknob, phone handset, hands of the person you shake hands with etc. etc.

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