zlacker

There's been a number of very short transmission chains. One of the things that's difficult for infectious diseases is that they have extremely long-tailed distributions. "This has happened before, and it got a couple people sick" is a distinct possibility. It also happens relatively frequently with diseases that have a lower pandemic potential than a coronavirus.

So the answer to "What makes COVID special?" is possibly "We failed our pandemic save."

I did some research during the early stages of the West African Ebola epidemic, when a lot of people were asking why, instead of the usual sporadic, self-limiting outbreaks of the past, we were seeing something larger and different. As it turns out, if you use the parameters people estimated from the older, smaller outbreaks, there's a small but not breathtakingly so probability of a very large epidemic. It's sort of the null hypothesis for pandemics.