Eric Greenwell wrote:

Recently, I've begun to wonder if some pilots are experiencing sickness
caused (or at least increased) by a contaminated water container....snip

Plausible? Is there any evidence?

Yes, Eric, I think you're quite right. I've seen some Camelbak tubes
which are almost completely opaque with some form of living crud! A
friend who was sick at a comp suspected a dirty water bladder - and the
problem stopped when he changed to a clean, new one.

Since they can never be drained completely, I've taken to emptying my
bladders and tubes and putting them in the freezer when they're not in
use. So far, no crud after several years - and no sickness.

GC