“ Symptoms usually begin 1 to 3 weeks after exposure”

Water now will let you get to treatment next week.

I second this; a couple of years back I went hiking with a buddy, we had water but planned for a day hike that extended overnight, and we had to drink water from some streams. While I worried about illness, having water then meant we were able to get back to civilization, where if we got sick we could seek medical attention.