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This is Scientific Americans, 60-second science. I'm Steve Merski.

Here in New York, the coronavirus cases are exploding. We're on the steep part of the curve.

Now, you've probably heard about the basic reproduction number, R0 or R0.

And that's basically how many people, an infected person, goes on to infect themselves.

And the other night, I happened to see a tweet that showed just how big a difference there is

over 10 cycles of transmission between a basic reproduction number of 1.3 and a basic reproduction number of

three. The difference was astounding. The 1.3 after 10 cycles infected, on average, 14 other people

total. The basic reproduction number of 3.0 led to 59,000. Looking at those numbers was

startling. So I got a calculator out. And I'm going to repeat this exercise that I did with the

calculator. And you can do it too. It's even a little bit fun and it's kind of amazing. So I've got two calculators because I'm going to do the two different basic

reproduction numbers, the R-0s, together.

Okay, so the calculator on my left, I'm going to assume 1.3 as the basic

reproduction number. Each person infects 1.3 other people on

average. The calculator on the right, I'm going to do 2.5, just to pick a number, and because that

looks like it may be fairly close to what the coronavirus number is. So we'll start with one person on each side.

We multiply by 1.3 on the left to get 1.3, obviously. We multiply by 2.5 on the right to get, not

surprisingly, 2.5. For cycle 2, we multiply the one on the left by 1.3 again, and we get 1.69.

...