Books and Viruses

Thanks to COVID-19, more of us know about R₀—or at least we should. As The Harvard Global Health Institute puts it:

R-naught calculates how fast communicable diseases spread. It represents, on average, the number of people that a single infected person can be expected to transmit that disease to. In other words, it is a calculation of the average “spreadability” of an infectious disease.

If that definition doesn't wet your whistle, try Wikipedia.

Either way, as we learned in the early days of COVID-19, when it comes to viruses, a large R-naught means trouble. If it's ten, then every person exposes the disease or virus to 10 others. Ten becomes 100, and then 1,000, and bad things happen. An R₀ of 0.2, however, means that ten people expose the virus to 2, who then expose 0.2 people. If we can flatten the curve, then we can avert a crisis.

Changing the Lens

Think about R₀ in a very different context, however: books.