Re[4]: [at-l] Water filters...

[Bob C." <ellen@clinic.net (Bob C.)]

Rick: Many thanks for an excellent reference. The key message to AT hikers
strike me as:

" The water that wilderness travelers are apt to drink, assuming that they =
use a
little care, seems almost universally safe as far as Giardia is concerned. =
The
study referred to earlier, in which the researchers concluded that the risk=
 of
contracting giardiasis in the wilderness is similar to that of a shark atta=
ck,
is telling. What they did find is that Giardia and other intestinal bugs ar=
e for
the most part spread by direct fecal-oral or food-borne transmission, not b=
y
contaminated drinking water. Since personal hygiene often takes a backseat =
when
camping, the possibility of contracting giardiasis from someone in your own
party=97someone who is asymptomatic, probably=97is real. Recalling that up =
to 7
percent of Americans, or 1 in 14, are infected, it is not surprising that
wilderness visitors can indeed come home with a case of giardiasis contract=
ed
not from the water=85but from one of their friends.

"This theme, that reduced attention to personal hygiene is an important fac=
tor
for contracting giardiasis in the wilderness, is becoming more frequent in =
the
literature.

"Outside of the Sierra, Giardia cysts in concentrations =93as high as four =
per
gallon =94 have been detected in untreated water in northeastern and wester=
n
states.  But even with this concentration, one would have to consume over n=
ine
liters of water to have a 50 percent chance of ingesting 10 or more cysts.

Indeed, there may be as much unwarranted hysteria surrounding Giardia in
wilderness water in these other areas as there is for the Sierra. For examp=
le,
an oft-cited report describing acquisition of the disease by 65 percent of =
a
group of students hiking in the Uinta Mountains of Utah is now viewed with
considerable skepticism. Specifically, the attack rate was far beyond that
usually seen with water-contracted giardiasis, no cysts were identified in =
the
suspect water, there was no association between water consumption rates and=
 the
likelihood of the disease, and the authors categorically discounted food-bo=
rne
or fecal-oral spread, stating that it had never been reported (correct at t=
he
time).

  Weary