The National Outdoor Leadership School has recorded about one incident per 5,000 person-field days by following strict protocols on hygiene and water treatment.
[5] Based on reviews of epidemiologic data and literature, some researchers believe that the risks have been over-stated and are poorly understood by the public.
[citation needed] Most cases begin abruptly and usually result in increased frequency, volume, and weight of stool.
Other commonly associated symptoms are nausea, vomiting, abdominal cramping, bloating, low fever, urgency, and malaise, and usually the appetite is affected.
Life-threatening illness resulting from WAD is extremely rare but can occur in people with weakened immune systems.
[citation needed] Infectious diarrhea acquired in the wilderness is caused by various bacteria, viruses, and parasites (protozoa).
[14] Many other varieties of diarrhea-causing organisms, including Shigella and Salmonella typhi, and hepatitis A virus, can survive freezing for weeks to months.
[15] Virologists believe all surface water in the United States and Canada has the potential to contain human viruses, which cause a wide range of illnesses including diarrhea, polio and meningitis.
[citation needed] A suspected case of wilderness-acquired diarrhea may be assessed within the general context of intestinal complaints.
[21] There are an estimated 99 million annual cases of intestinal infectious disease in the United States,[22] most commonly from viruses, followed by bacteria and parasites, including Giardia and Cryptosporidium.
[1] Water can be treated in the wilderness through filtering, chemical disinfectants, a portable ultraviolet light device, pasteurizing or boiling.
[citation needed] In a study of long-distance backpacking, it was found that water filters were used more consistently than chemical disinfectants.
[citation needed] Iodine resins, if combined with microfiltration to remove resistant cysts, are also a viable single-step process, but may not be effective under all conditions.
New one-step techniques using chlorine dioxide, ozone, and UV radiation may prove effective, but still require validation.
Some hikers use small portable UV devices which meet the U.S. EPA Guide Standard and Protocol for Testing Microbiological Water Purifiers, for example, the SteriPEN.
Various studies have sought to estimate diarrhea attack rates among wilderness travelers, and results have ranged widely.
[35] In contrast, a survey of long-distance Appalachian Trail hikers found more than half the respondents reported at least one episode of diarrhea that lasted an average of two days.
Campylobacter enteritis occurred most frequently in young adults who had hiked in wilderness areas and drunk untreated surface water in the week prior.