Once there was a time, days of freedom and ignorance vaguely remembered as the 70’s, when we didn’t worry about wilderness water quality. We drank when and where we pleased. Yes, there was a tale of backpackers in Utah who became ill with “beaver fever” caused by Giardia, but we tried to ignore this challenge to our assumptions. The die was cast, however, and discussions began over whether we needed to disinfect the water.
Physician and outdoor educator Thomas Welch wrote an editorial on water disinfection in the Journal of Wilderness and Environmental Medicine 2004. He points out that this classic 1976 Utah incident of Giardia caused diarrhea, which brought this protozoa to our attention and probably sparked the water disinfection era, looks in hindsight like a hygiene, not a water disinfection problem. Other groups using the same area didn’t get sick, cysts could not be isolated from the water, and the patients all became ill at the same time, and with a short incubation period, suggesting this was not a waterborne protozoa illness.
Giardia’s reputation is enhanced by an association bias. People go camping, get diarrhea and assume the source was the water. This perception is encouraged when the diagnosis of Giardia is based on a history of a recent camping trip, but without testing. The patient leaves believing they may have Giardia, when in fact there is often no proof. They leave thinking it was the water they drank, when the cause of the illness may have been hand-to-mouth transmission. They might need a lecture about hand washing from their health care provider, along with the advice to be more diligent with water disinfection.
The editorial makes the point that water disinfection is not a substitute for hand washing or alcohol-based hand cleaners.
Someday we may have the science to give us a better sense of when we need to disinfect water. Until then, routine water disinfection has low health risks and is prudent. And hygiene, especially hand washing, is vital for avoiding illness on a wilderness trip.
Welch, TR. Evidence-based medicine in the wilderness: The Safety of Backcountry Water. 2004. Wilderness Environ Med. 15:235-237.