system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How did diarrhea kill so many people before and now it’s not that big of a deal?

Title really, is it just that our diet is better and decent food is much more abundant or is it just general hygiene?
gpt
Diarrhea causes dehydration, easy fix is to just drink more water right? Well(no pun intended) your water source may be what gave you the diarrhea bug to begin with. If you have another water source you may be able to let the bug run it’s course, but drinking from the same contaminated water will just keep reintroducing what’s giving you the Hershey squirts so your body can never really deal with it properly. Today, we treat drinking water for that sort of thing, and have better medicine if you do catch it by drinking out of a pond or something.