By Ramon P. DeGennaro, Phd
popular link circulating on the internet shows the results of a demonstration. Dr. Richard Davis sneezed, sang, talked, and coughed into agar cultures wearing a standard surgical mask, and again using no mask. The result is a powerful image: The cultures without the mask clearly show more microorganism growth.
The strongly worded conclusion from the post’s author? Wear a mask. That way, “Lives will be saved.”
A picture is worth a thousand words, but a picture is not a good substitute for thoughtful analysis. Does the image actually support the conclusion? Or even worse, is the image misleading, steering you to an incorrect conclusion?
Indeed, Dr. Davis’ own conclusion of his demonstration is considerably less emphatic than the author’s: “A mask preventing your spit & breath from flying out of your mouth, even if doesn’t catch it all, will stop some spread of bacteria (see [in this demonstration]) AND LIKELY VIRUS (not seen [in this demonstration]).” ~ Rich Davis, PhD, D(ABMM), MLS June 27, 2020, emphasis in the original.
That’s far less powerful. First, as Dr. Davis is careful to say, the cultures show bacterial growth, not viral growth. Bacteria are much larger than viruses, so a test showing that a mask blocks bacteria gives us no direct evidence that masks help block COVID-19 and other viral infections, such as the flu.
This doesn’t mean the demonstration is necessarily irrelevant for viral infections. But to inject a dramatic photo of bacterial cultures into the COVID-19 conversation is at best misleading. Masks may or may not be a good idea for you, but Captain Michael Doyle, the commanding officer of a coronavirus testing site, says, “The only mask that the CDC considers safe from you getting the coronavirus, the only way to actually prevent you from inhaling it, is the N95 mask.”
So, based on Captain Doyle’s statement, should we not bother to wear a mask? Again, masks may or may not be a good idea for you, but his statement is also potentially misleading: Although Captain Doyle is absolutely correct, he is discussing whether the mask protects the wearer. Perhaps we should consider those around us.
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