[SeekAndFind]

For the mathematically inclined:

R0 ∝ t × c × d

None of these three numbers are things we can directly measure, especially in the course of an epidemic spread, but we can take other information and estimate it using models. The key point here is that R0 by definition represents the number of new cases following an individual case.

That turns the progress of an epidemic into a familiar equation:

number of new cases = number of starting cases × R0n

where n is the number of "generations".

If that doesn't look familiar, look at your credit card bill. It's the same way interest is calculated — (1+r)n. R0 here is just principle and interest.

[wastoute]

Yes, epidemiology. No measure of “velocity”. Because every epidemic ever studied was retrospective. Now we desperately need a measure of velocity and not one with a lot of initegrals and Sigmas. The truest indicator I can think of is how many days until the number of dead each day doubles. That’s what I am watching.