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The Swiss Cheese Defense Against Airborne Viruses

Swiss Cheese Metaphor

You may recall we mentioned recently that the COVID-19 virus only gets faster and stronger and better at aerosol transmission? Well, as if to prove the point, a new COVID-19 variant of concern has been identified (CDC).

In light of the newly identified Omicron variant of SARS-CoV-2, we’d like to re-up a metaphor we’ve used and appreciated quite a lot this year:

The swiss cheese metaphor

Protection against COVID-19 (in all its various forms) is like Swiss cheese. Specifically, it’s like a block of Swiss cheese made up of individual slices.

In this metaphor, each slice is one effort put forth to slow the spread of this disease.

Masks are one slice. Vaccines are another slice. Social distance is yet another slice. You get the idea.

Ventilation is another slice. HEPA filtration air cleaning is another slice.

And so on.

The thing about each slice is that there are holes (because it’s Swiss cheese). A slice will block some aerosols, but some will sneak through those holes.

The next slice has a different set of holes; those aerosols that snuck through the previous slice are far less in number, but again, since there are holes in the next slice, a few will get through.

No single slice offers perfect, 100% protection from a virus. The key is to have so many slices that the block of cheese is, ultimately, as solid as possible. As the infographic points out: multiple layers improve success.

HEPA filtration


Additional protection


Illustration and descriptions by Dr. Ian M. MacKay, PhD, et al. (, et al.) – Read more from the original source here: The Swiss cheese infographic that went viral

This image was first brought to our attention by Dr. Kimberly Prather, PhD, and we encourage everyone to share this image as well!

CDC Science Brief: Omicron (B.1.1.529) Variant

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