How to Read Epidemiological Parameters

Basic guide for using CDC data to understand how many people must die for a society to reach herd immunity.

David J. Sencer CDC Museum in Atlanta, GA (public domain image from Jim Gathany, downloaded from Wikimedia Commons)

An epidemic is not a single number. Knowing exactly how bad an epidemic is requires knowing both how quickly it is going to spread and how bad its effects will be on those who are affected by it. To make matters worse, parameters that characterize each of these separate factors usually…