system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it so unsafe to drink untreated water in the wild today? Haven't humans been drinking any available water since the beginning? What has changed?
gpt
It was never safe to begin with.  Historically, and today in parts of the world lacking safe drinking water supplies, water-borne illnesses are a major problem and a major cause of sickness and death, especially in children.  People just didn't/don't have any other choice but to take the risk.