Re[2]: [at-l] Re: water filters...

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

I don't know how easy it is to detect other bugs that can make a hiker sick, but
according to the above study "Giardia cysts in concentrations as high as four
per gallon have been detected in untreated water in northeastern waters."

That suggests to me that "small, sterile sample bottles" are unlikely to find
giardia cysts even in seriously contaminated streams.

The sparse concentrations may also explain why so few hikers seem to have
confirmed cases of giardiasis. The study suggested that it generally takes 10
cysts to infect a human. At four per gallon or less, one has to drink an awful
lot of contaminated water to have any likelihood of ingesting enough cysts to
make a hiker sick.

Since people in third world countries, who regularly drink from giardia infested
waters, tend never to have symptoms, that suggests that immunization occurs at
some point. Those of us who have spent considerable time in the outdoors, may be
immune.

Weary