> Most epidemics disappear once populations achieve herd immunity and the pathogen has too few vulnerable bodies available as hosts for its self-propagation. T

> Most epidemics disappear once populations achieve herd immunity and the pathogen has too few vulnerable bodies available as hosts for its self-propagation. This makes it sound like most pandemic diseases reach a point where they essentially go extinct, but my understanding is that's not really accurate. They typically just reach an equilibrium where the negative effects fade into the background noise of general illness. This is what happened with the four human-endemic Coronaviruses which likely caused major pandemics in their time, but now fade into the background of cold season.