One of the most amazing disease-related things I've ever read was something about cholera (of course I will never remember the original source), and the fact that it doesn't have to be fatal at all, so long as you rehydrate properly. Apparently in the vast majority of cases the body will fight off cholera just fine, so long as it doesn't run out of fluids in the meantime. If only people had known that they couldn't just drink plain water...

The (possibly apocryphal) article also went into modern educational efforts in rural India, where people were being taught the proper handfuls of sugar and salt to add to water, to combat cholera there.