Seneca, the Roman philosopher, knew the term “virus,” that for him had the meaning of our term “poison.” But of course, he had no idea that a virus, intended in the modern sense, was a microscopic creature reproducing inside host cell. He also lived in a time, the 1st century AD, when major epidemics were virtually unknown. It was only more than one century after his death that a major pandemic, the Antonine Plague, would hit the Roman Empire.
But Seneca was a fine observer of nature and when he said that “ruin is rapid” he surely had in mind, among many other things, how fast a healthy person could be hit by a disease and die. Of course, Seneca had no mathematical tools that would allow him to propose a quantitative epidemiological theory, but his observation, that I have been calling the “Seneca Effect,” remains valid. Not only people can be quickly killed by diseases, but even epidemics often follow the Seneca Curve, growing, peaking, and declining.
Of course, the concepts of growth and collapse depend on the point of view. In many cases one man’s fortune is someone else’s ruin. What we see as a good thing, the end of an epidemic, is a collapse seen from the side of the virus (or bacteria, or whatever). But, then, why do epidemics flare up and then subside? It is a fascinating story that has to do with how complex systems behave. To tell it, we have to start from the beginning.
One thing that you may have noted about the current Covid-19 pandemic is the remarkable ignorance not just of the general public about epidemiology, but also of many of the highly touted experts. Just note how many people said that the epidemic grows “exponentially.”…