Risks of COVID-19 exposure by group size

This has a good graph showing risk of SARS-CoV-2 exposure by group size depending on community prevalence.

The article is here.

Note that the graph is logarithmic—that means it increases by powers of 10 (100, 1000, 10 000, etc) not linearly (1,2,3). So, a straight line is an exponential curve on a regular graph.

This illustrates why as we open economic activity back up, self-isolation and keeping our family’s “contact bubble” as small as we can remains important.

it also shows why I don’t think things like church services, concerts, or sports events will be happening for quite some time yet.

Lethbridge hospital has its first COVID case in ICU, and it isn’t an “old person” from a nursing home. We’ve expected that our real risk period would start a bit behind other areas, so this may be the start of our “surge.”

The meat packing plant outbreaks are a good example of what we’ve by and large avoided through social distancing. We can’t keep doing what we’ve done for long, but we should avoid the sense that everything can go right back to normal. That will probably just prolong or worsen the agony.

As Churchill said at one point in World War II, we have not reached the beginning of the end, but we’ve probably reached the end of the beginning.

(This is US data, but the same statistical principles will apply everywhere.)