Well, although the most prevalent example right now is of course the coronavirus pandemic, events like this have happened all throughout history. Think of the Black Death: it swept through Europe, killing tens of thousands and pretty much ending the system of feudalism. Though in modern times these pandemics have less potential to upend systems, they remain game changers. The H1N1 epidemic - the Spanish flu - sent shockwaves throughout the globe because of its scope and lethality.
