Water water water

Water purification

I attended the Northeast Wilderness Medicine Conference on October 14. Dr. Tom Welch (his website is adirondoc.com) gave a great talk about water. So, is Giardia much of a risk? Well, it turns out that the original study about a supposed water-borne outbreak of giardiasis among backpackers was flawed. It wasn’t the water, it was surfaces contaminated by the hands of someone (or someones) who harbored giardia. You need 10 giardia cysts to become infected, and even contaminated water has perhaps 1-2 cysts in a few liters.

The take home messages for me: You don’t have to worry about catching giardia from a few drops of water on the threads of your water bottle. But don’t let other hikers touch your water bottle. Or your food. (Another study showed that 1/3 of backpackers have fecal contamination of their hands.) The only water purification method that eliminates viruses is chemical treatment. And viruses are the number one cause of wate-borne intestinal illness. If you want to treat your water by boiling, you  don’t have to boil it for minutes. Just bring it to a boil. Because that’s 100 degrees centigrade, and all you really need is to get the water above 60 degrees centigrade to denature proteins and kill organisms.


Well, this is sort of tech gear. I realize that when I hit the trail next year, I will probably blog via my iPhone. So how to edit my pictures to 660×330 for the blog? I tried one solution today, an app called Crop-Size. It worked easily. The caveat? I could crop my image, which meant only a little portion of the actual image would be used. Rather than resizing it – shrinking the whole thing down to a small size. But it’s a start. This post was created via computer. And the featured image was taken today with my “real” camera (digital SLR which I won’t be hauling on the AT!). But it was so much nicer than the iPhone pic that I also snapped at the same time.

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Comments 3

  • Buck Nelson : Oct 17th

    With all due respect to you, Dr. Briggs, Dr. Welch is a major source of misinformation on backcountry water. He fooled me, like many others, until I got giardiasis and did my own research. The real experts, professional epidemiologists, have very different conclusions.

    That outbreak he talked about? It WAS a CDC verified waterborne outbreak. To have a foodborne outbreak, as he claimed, infected people should be in the same food sharing group. They weren’t. But all the infected persons drank from the same stream which was downstream from a beaver lodge. https://bucktrack.blogspot.com/2012/09/backpacker-giardia-debunking-skeptical_8.html There have been other CDC documented backcountry water giardiasis outbreaks as well, regardless.

    Dr. Welch’s claim about dirty hiker hands? Well they weren’t as dirty as when they started their trip, or as dirty as the hands of British commuters. https://bucktrack.com/water.html The only study of which I’m aware (“Medical risks of wilderness hiking”) that compared hygiene to water treatment found water treatment was a greater factor in backpacker health. It’s a false choice anyway, both are important.

    You don’t need to ingest 10 giardia cysts to become infected as Dr Welch claims, the best science says there is some risk with a single cyst. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1405147/pdf/amjph00206-0039.pdf. And studies have found as many as 26 cysts per liter from a river characterized as pristine.

    If he’s saying viruses are the greatest concern in backcountry water, that’s another of his manufactured facts. I have studied this topic at length and to the best of my recollection I haven’t even heard that hypothesis, let alone seen a peer-reviewed paper supporting such a claim.

    All this isn’t just one person’s opinion. The CDC specifically refuted Dr. Welch’s research saying: “Although the advice to universally filter and disinfect backcountry drinking water to prevent disease has been debated, the health consequences of ignoring that standard water treatment advice have been documented…”

    • sggrirb : Oct 19th

      I won’t debate you here, but I’d suggest you take it up with Dr. Welch himself. I still think the evidence of risk for giardia among campers tends to be overstated.

      Better to worry about fecal contamination and norovirus. https://thetrek.co/norovirus/

      Or for a more nuanced discussion than I have time for, about giardia and other risks of backcountry water:


      • Buck Nelson : Oct 21st

        I checked out the links. I don’t think bloggers and retailers are the best place to get medical advice. I trust the CDC unless I have specific, verifiable reasons not to.

        REI is making a mistake in presenting the science behind backcountry water treatment as a “tie.” It’s not.

        Dr Welch takes an extreme view that does not stand up to scrutiny and contradicts the CDC and every other public health agency in North America as far as I know. Both sides cannot be right.

        I have exchanged emails with Dr. Welch. He won’t debate me either, likely because of his weak arguments. If he changes his mind, I’ll happily debate him right here.

        Better to worry about fecal contamination? Backcountry water is frequently fecally contaminated. That’s where giardiasis and several other pathogens in the water come from.

        Hygiene vs clean water is a false dichotomy in any case.

        Here’s a link to most of the peer reviewed scientific papers on the subject. https://bucktrack.com/water.html


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