Ask a Virologist: Found Water on the Trail, Is it Safe?

I recently spoke with J. David Beckham, MD and Assistant Professor in the Infectious Diseases Division at the University of Colorado Denver School of Medicine about hydration issues during outdoor activities in Colorado. He is an avid mountain biker, hiker and camps frequently with his wife, 2 young sons and 2 dogs.

Colorado enjoys plenty of warm, sunny days, perfect for exploring the mountains and trails throughout the state. With all that sun comes serious hydration concerns. It’s too easy to run through an entire pack before you’re “out of the woods”. We discussed some of the issues and risks associated with found water, and what you can do to mitigate those risks.

JZ: How great is the risk of illness from improperly filtered water on the trail?
DB: Risk of diarrhea illness is significant from drinking unfiltered or improperly filtered water from rivers and streams. Most common illness are self-limited and related to infection due to giardia, cryptosporidium and some bacterial pathogens including campylobacter and less commonly e. coli.

JZ: What contaminants might be in water you find on the trail?
DB: Giardia and cryptosporidium are the most common infections but depending on the water source, bacterial causes of illness are common as well.

JZ: What can happen if you ingest contaminated water you find on the trail?
DB: Diarrheal illness is by far the most common. The loss of fluids from vomiting and diarrhea with insensible losses and decreased oral intake can result in significant water losses and significant illness.

JZ: How can you tell if you are dehydrated or have a water-borne pathogen infection?
DB: Dehydration is often associated with headache, confusion, dizziness, and  loss of consciousness in severe cases. Water-borne pathogen infections can be associated with fever, diarrhea, vomiting, abdominal pain, loss of oral intake and dehydration.

JZ: What action can you take to cure dehydration/infection? Any natural/in the field remedies?
DB: Curing dehydration/infection often involves appropriate anti-parasitic or antibacterial treatment but this is secondary to volume fluid replacement with either intravenous fluids or oral rehydration solutions in the field. In cases of cholera outbreaks, oral rehydration solutions consisting of glucose, sodium chloride and water have been show to be as effective as IV hydration.

JZ: What concerns should hikers have about sharing water with each other?
DB: Water sharing can increase the likelihood of pathogen transmission between hikers.

JZ: Are you confident relying on an inline filtration system, being able to fill your pack from a stream and have it filter thru the line and be immediately potable? Why or why not?
DB: Yes and No. This is a complicated question and answer. First, the inline filtration system used for this pack is a basic carbon filter which will filter most pathogens found in lakes and streams. The main concern with this approach involves the dwell time of the nonpotable water in the pack. Basically, when the water reservoir is filled with nonpotable water, my main concern is that the increased dwell time in the reservoir could allow bacterial replication, increased bacterial load and subsequently overload the filter capacity of the carbon filter. If lake or stream water is allowed to dwell in the reservoir for a long period of time (12 to 24 hours), bacterial replication in the pack would overload the carbon filter and result in transmission of bacteria from the reservoir to the person drinking the water. Many of these bacterial pathogens require a low innoculum to cause infection in humans, especially campylobacter.

This can be studied by filling the reservoir with nonpotable water and taking quantitative bacterial cultures from the reservoir and the post-filtered line at time points over a 24 to 48 hour period. This would provide a growth rate in the reservoir and an estimated time for bacterial growth to overcome the carbon inline filter.

JZ: Some of the problems a spray nozzle solves are…
DB: Problems with contamination of the nozzle and sharing with friends if needed while on the trail.

JZ: Some other instances (non-drinking) where clean filtered water would be important are….
DB: Wound care, hygiene, and food preparation

JZ: Speaking of wound-care, are there any dangers from these guys: giardia, cryptosporidium, campylobacter, e. coli. etc., if you are using untreated/found water for wound care?

DB: Diarrhea pathogens like giardia, crypto, campy, and ecoli will not cause wound infections. But other bacteria in the water could cause wound infections such as clostridium, pseudomonas, aeromonas, etc.

JZ: Thinking about extended use, refilling the bladder with found water multiple times, if you turned the bladder inside out and exposed it to the sun, would that reduce the possible bacteria load?

DB: The sun probably wouldn’t help but turning the bladder inside out and allowing it to dry between use would really help decrease potential contamination. Many companies claim that the bladder material is ‘antibacterial’ but the treatments they use won’t help much for some/many water sources such as standing water. Stream water that is moving over rocks usually has lower bacterial loads. Standing water, warm, shallow water and thermally polluted water are more likely to have a higher degree of bacterial contamination or higher bacterial loads.

When You Might Get Sick

It’s important to note that if you become infected on the trail, it is unlikely to happen immediately. Most day hikers won’t realize that they have acquired a pathogen  on the trail and may likely attributed to a bad meal eaten a few days later. This is good news for those of us who are going to be in the comfort of our homes with ready medical access if we are hit.  No one wants to get sick, but for but for hikers and campers out for multiple days in a row without access to medical help, these infections be devastating.

Below are the common incubation periods for the pathogens discussed above:

Giardia: 1-3 weeks
Cryptosporidium: 1-12 days, commonly 7 days
Campylobacter: 1-11 days, commonly 2-5 days
E. coli.: 1-10 days, commonly 2-5 days

What You Can Do

In this as in most things, the best defense is a good offense. Follow this tips to stay hydrated and healthy on the trail:

• Bring enough water to cover your needs (and the needs of those in your care) during your trek, plus a little extra, just in case.
• If there is any chance that you will need to drink found water, bring an inline filter (and/or water treatment tablets).
• If you need to use found water, moving water (found in streams) is preferable to standing water.
• If you use an inline filter to treat questionable water, try to drink/use that water within 10 hours to reduce any bacteria’s time to replicate an potentially overwhelm the filter.
• If you find yourself needing to refill the bladder with found water multiple times: Empty the bladder completely and turn inside out to allow to dry thoroughly to help reduce bacterial overload. Spray some water through the tube before drinking.
• If you need to use found water for wound care, filter it to reduce infection from bacteria. Again, stream/moving water is preferable as it will carry a lower risk of bacterial infection than standing water.

What are your thoughts? Any experiences to share? Any questions for Dr. Beckham, I’ll ask!