For every person you contact, you are indirectly contacting every other person they contact.

This is what I’m calling your ‘exposure circle.’ The more people you contact, the more your circle grows–exponentially.

The fundamental goal of social distancing is to
1) shrink each of our exposure circles and
2) minimize overlap of different exposure circles (and unless we only see people who only see us, every circle is different).

At this point we should assume community spread of SARS-CoV-2, the virus that causes COVID-19 illness. Travel to and from ‘hotbed’ areas is likely no longer the main source of new infections.

Each infected person is thought to infect, on average, 2 additional people (the basic reproduction number, or R0=2), so spread is exponential.

If you have a hard time picturing what this looks like, go to the last page of One Grain of Rice A Mathematical Folktake by Demi.  You can see the grid on Amazon by clicking the “Look Inside” icon.  Doubling one grain of rice every day yields over 536 million grains of rice on day 30, and over 1 billion total grains accumulated over all 30 days.

Because we have not been able to test widely in the United States, we cannot know who is infected and who is not. So targeted isolation is not feasible.

It may very well be that young healthy people are infected and don’t show symptoms, so they spread to many others out in community without knowing.

This is why school closures should NOT be seen as vacation, license to go shopping, eating out, seeing movies, partying, etc.

THIS is why we need to keep our distance from one another–all of us.

I know it sucks. I know it’s incredibly disruptive and feels like overkill. If it works, nothing will be that bad and we will think, why did we do all of that?

And that is, of course, the goal.

If we succeed, we may never know how bad it could have been.

If we fail, we will see all too soon and it will be too late to regret.