The primary necessity for survival is the availability of air. Once you have air to breathe, water, food, and shelter become the next requirements for your continued existence on the planet; that is, clean water and properly prepared food.
Even in normal times, there are many instances where an outbreak of infectious disease occurs due to water of poor quality. Ingesting food that was incompletely cooked caused the deaths of medieval kings in medieval times and may even have sparked the Ebola epidemic in 2014.
Epidemics caused by organisms that cause severe diarrhea and dehydration have been a part of the human experience since before recorded history. If severe enough, dehydration can cause hypovolemic shock, organ failure, and death. Indeed, during the Civil War, more deaths were attributed to dehydration from infectious diseases than from bullets or shrapnel.This post was originally published on this site