Connect with us


Backpackers, Don't Listen To Slate: Science Does Support Stream Water Treatment

The risk might be low, but the alternative is maybe months of debilitating diarrhea. It’s your choice. Photo Credit: Timothy Epp/Shutterstock

While we like to think of ourselves as rational creatures, there’s no doubt that human beings are actually quite awful at assessing risk. So I can understand why Ethan Linck thought to contextualize the risk of drinking from backcountry streams with data. “Life is triage, a constant series of negotiations between risks of varying severity,” he wrote. “And how we talk about those risks matters.”

Yes, it does—which is exactly why his piece in Slate last week was so damaging. It was anything but a careful, scientific evaluation of the risks. Wes Siler over at Outside Magazine already pointed out a myriad of issues with the article, but I want to zero in on the actual data, because Linck claimed to be looking at the matter scientifically. Instead, he cherry-picked sources to argue against doing one of the simplest things you can do to protect yourself from some truly awful diseases when you’re backpacking: treating your water.

Last week, @Slate published an article that said backpackers don’t need to filter stream water. That’s simply not true.

— Outside Magazine (@outsidemagazine) February 7, 2018

The Bad

Simply put: when you drink water straight from a stream, river, or lake, you have no idea what’s in it. And that’s bad, because, as epidemiologist Tara Smith, PhD, explained for SELF last month, it can be contaminated with all sorts of nasty things. “These include Giardia, a parasite found in streams and rivers that causes “beaver fever” in campers and hikers, and bacteria like Shigella and Campylobacter that can cause bloody diarrhea,” she wrote.

These organisms exist in waters because they exist in our digestive tracts and those of other animals. So anywhere that there’s poop near water, that water could contain pathogenic strains of Escherichia coli, Salmonella, Campylobacter, Aeromonas, Yersenia enterocolitica, Leptospirosis, Listeria, or Vibrio, in addition to a suite of viruses and protozoan parasites like Giardia and Cryptosporidium. Some of these bugs only cause short-term, if severe, gastrointestinal distress. Others can cause issues that last for weeks, months, or even years.

“Even water that appears pure or clear can be contaminated by people or animals,” explains Jonathan Yoder, MPH, who is deputy chief of CDC’s Waterborne Disease Prevention Branch. I asked Yoder and his colleague, epidemiologist Kathy Benedict, PhD, what their thoughts were on the bold claim that science doesn’t support backcountry water treatment (that “the scientific evidence shows that this mandate [to filter water] rests on a shaky foundation”). Needless to say, they disagreed.

Because appropriately assessing risk requires a clear understanding of what’s at stake, it’s important to point out that with many of these pathogens, we’re not just talking inconvenient cases of the runs. The gastrointestinal symptoms that can occur—intense diarrhea, vomiting—aren’t easily managed by hikers on long trips in the middle of nowhere. “If they have an acute situation, it can actually be quite scary,” says Benedict, “especially if they’re out there by themselves, because they can get themselves into a lot of trouble very quickly.” And people, even people with rapid access to medical care, do sometimes die.

A 3D rendering of Giardia lamblia a protozoan parasite that can set up shop in your intestines and be pretty hard to remove. Image Credit: fotovapl/Shutterstock

A 3D rendering of Giardia lamblia a protozoan parasite that can set up shop in your intestines and get pretty comfortable there. Image Credit: fotovapl/Shutterstock

To his credit, Linck doesn’t exactly downplay the dangers of Giardia or other potential pathogens. But, he argues, that their dangers are not important. It’s totally ok to drink any water you might come across while backpacking (or as the title says, “You Don’t Need to Filter Your Stream Water”) because: “The idea that most wilderness water sources are inherently unsafe is baseless dogma, unsupported by any epidemiological evidence”.

It’s a lovely little straw man that he immediately sets to tearing apart. To paraphrase his argument: everyone says most water is chock full of terrible things. So as long as most water sources are safe, then you’re good to drink from any stream. And look! Here’s a study that says feces contamination was only found in a minority of the sites tested! And one by… a magazine… that says the same thing!

But let’s take a quick look at those sources. The first study examined lakes and streams in Kings Canyon, Sequoia, and Yosemite National Parks looking for feces-associated bacteria (fecal coliform), because where there’s feces, there could be something dangerous in the water. And they found it at 22 of the 55 chosen sites. So yes, that’s a minority, but it’s 40%—and of those, ~16.3% (9) had “higher levels”. And that magazine one? Well, Linck didn’t directly link to it, but Google is a wonderful thing. They surveyed seven locations three times throughout the year for parasites, five of which had at least one test come up positive for either Giardia or Cryptosporidium—just over 71%. But, they claimed, only one had close to dangerous levels. That’s still 1/7—or a little over 14%. It’s a shame that Linck didn’t include the percentages in his article, because for all his talk about appropriately assessing risk, he doesn’t give the information needed to actually do that.

And those studies—if you can really call the magazine investigation that—were conducted in the early 2000s, each testing a miniscule fraction of the waters that are accessed by U.S. hikers every year on a handful of occasions. There is other research he could have cited—like this 2009 study from Georgia, which found 79% of water samples from rivers and streams in southern Georgia over a year tested positive for Salmonella. Or this 2011 one which found “Salmonella, Campylobacter, Staphylococcus aureus, Vibrio vulnificus, and V. parahaemolyticus were widespread—12 of 22 O’ahu streams had all five pathogens.” And even if he didn’t want to count Hawai’i (though it is a U.S. state), then he could have cited this 1987 study in Washington instead, which found Campylobacter at ~36% of sites tested (5 of 14), including a mountain stream. According to the authors, “Campylobacter spp. are widely distributed in central Washington and are present in a variety of aquatic habitats including ponds, lakes, and small mountain streams, which ranged in elevation from 1,460 to 5,400 feet above sea level.”

Even if he just looked at other papers by the same authors as his study, he’d have found this 2004 study, which found that out of 31 backcountry sites, 45% tested positive for fecal coliforms, and just over 25% had high levels. Or this 2006 study which found fecal coliform at 1/15 sites used by backpackers (~6.7%). Or this one from 2008, which found coliform bacteria in 18% of human day use areas, and 14% of backpacker sites. But really, they all tell the same story: one-in-five to one-in-ten sites test positive, which means they might get you sick if you drink their water untreated.

Even the cleanest water can harbor these pathogens. Photo Credit: michaeljung/Shutterstock

Even the cleanest water can harbor these pathogens. Photo Credit: michaeljung/Shutterstock

Of course, even counting every sample in every study I just mentioned, only a tiny fraction of potential hiker drinking sources have been tested, so a lot remains unknown. And because these pathogens are associated with human and animal activities, their presence can be as transient as the wildlife. None of these studies really explains just how variable the risks can be, which is actually something that was noted in that Backpacker article:

“Risk in this area is very hard to quantify,” explains Tod Schimelpfenig, curriculum director for the Wilderness Medicine Institute, of the Wyoming-based National Outdoor Leadership School. “Sample a creek at one point in time and you could have a flush of organisms from an animal that just defecated upstream. Sample it 20 feet upstream 2 hours later and you could find nothing. The risk of drinking untreated water in the wilderness depends entirely on when and where.”

If any conclusions can be drawn, it’s that not all areas carry the same risks, and that even remote streams can harbor dangers. Even if you could assume something like 10%-20% of water sources test positive for fecal contamination (and thus may get you sick)—then, yeah, technically, only a minority of sites are ‘unsafe’ (not that anyone was arguing that most of them were). But just imagine going to a buffet and seeing a sign that said “Nine out of ten of our menu items tested negative for fecal bacteria!”—would you want to eat?

Yoder wouldn’t. Of course, he’s had Giardia before, so he knows exactly what he’d be risking. “I think after you have a one of the more severe diarrheal infections—and I speak from my personal experience—I think you understand that even though you know ninety-nine times out of a hundred, if you drank from that water source, you’re not going to get infected, it’s worth it to protect yourself for that one percent chance.”

The Ugly

While Linck’s prevalence analysis is a straw man at best, he goes on to claim something that’s patently false: that “research to date has failed to demonstrate any significant link between wilderness water consumption and infection with these threats.”

Again, he turns to decades-old data, citing a 1993 study where only 5.7% of backcountry travelers in California’s Sierra Nevada had Giardia, and none of them felt sick. Mind you, he failed to note that more than half of the travelers did purify their water, so they’d have been protected from the parasite. And he didn’t mention that 16.7% of them did return with gastrointestinal illnesses—they just weren’t that one. Then he cites a survey of health departments and a meta-analysis from the same researcher looking at Giardiasis in the US, both of which found that the majority of cases came from non-wilderness sources. But again, that’s a straw man—no one was arguing that backcountry streams were the main source of Giardia infections. That’s like saying most house fires aren’t started by deep-frying a frozen turkey, so by all means, it’s totally safe! And Giardia seems like a very specific hill to die on. What about the myriad of other possible disease agents? Nothing about Campylobacter, Leptosporosis, Shigella, Norovirus, E. coli—and the list goes on.

Heck, if we’re going back decades for our data, why not mention this 1984 study that found people who drank untreated water taken from a stream, river, or lake were about ten times as likely to have Campylobacter jejuni infections than their neighbors who didn’t? Or this 1983 one, which found both Campylobacter jejuni (23%) and Giardia lamblia (8%) in people who came back from Grand Teton National Park with diarrheal disease. They also found that Campylobacter occurred “most frequently in young adults who had been hiking in wilderness areas and was significantly associated with drinking untreated surface water in the week before illness” [emphasis mine]. They even isolated Campylobacter from one of the mountain streams suspected as a source.

You might not realize what has happened upstream. Photo Credit: Ruud Morijn Photographer/Shutterstock

You might not realize what has happened upstream. Photo Credit: Ruud Morijn Photographer/Shutterstock

Or, Linck could have looked at more recent data—like this 2016 study of Giardia outbreaks in the US from 1971-2011, which found six linked to rivers or streams. Or this 2017 study looking at waterborne illness outbreaks in the US in 2013 and 2014, which found another six outbreaks of Giardiasis affecting 91 people which were “caused by ingestion of water from a river, stream, or spring.” And these are just outbreaks where multiple people got infected and sought treatment—they don’t look at the countless individual cases, many of which are not reported to authorities because we don’t go to the doctor for diarrhea unless it’s really bad (diarrheal diseases are notoriously underreported). And it can take a week or more for signs to show in some cases, so you might not even connect your bowel troubles to your recent hiking experience.

Linck does mention a camping related outbreak of Giardia from 1976 which was thought to be waterborne. But he claims, citing a 2004 editorial, that the analysis was wrong. Instead, “the afflicted campers failed to properly wash their hands after using the bathroom.”

“I don’t disagree with the author that, in addition to water treatment, there are other very important things that people can do to stay safe in the backcountry,” says Yoder, “and those include the proper disposal of waste and using good hand-washing hand hygiene, particularly after using the bathroom and before eating before preparing food.”

By pointing to hand-washing, Linck is basically making the turkey argument again; the fact that poor hand-washing also causes outbreaks, maybe even more of them or worse ones, doesn’t mean that drinking untreated water never causes any.

In fact, the idea that every case reported from backpackers comes from poor hygiene instead of streams is not just hard to believe—it’s unsupported by the science. “We have data that there is a risk from backcountry water,” says Yoder. “There certainly are waterborne disease outbreaks—more than twenty that have been reported to CDC—where consumption of water in the backcountry has been linked to illness.”

The Good

The simple fact is, if you drink untreated water, you’re taking on a non-negligible amount of risk. The good news is that risk—however large or small it may be—can be mitigated. And no, not just with fancy filters.

Linck is quick to chastise the outdoors industry for “claiming the average hiker or camper needs a $99.95 microfilter pump to avoid illness and death.” Maybe expensive devices are talked up by their makers (are we really blaming companies for wanting to sell their products?), but luckily, the people that study waterborne diseases and pretty much everyone who has had any kind of training in wilderness survival will tell you that decent water treatment can be done a myriad of ways, many of which are dirt cheap. “Boiling water is one of the most effective ways to inactivate parasites, viruses, and bacteria,” Yoder notes. Or you could get chlorine dioxide tablets that treat a liter of water for about $0.50 each.

Boiling water goes a long way if you're going to be off the grid for awhile. Photo Credit: AlisLuch/Shutterstock

Boiling water goes a long way if you’re going to be off the grid for awhile. Photo Credit: AlisLuch/Shutterstock

Ultimately, the choice of what you drink is yours and yours alone. The point of this isn’t to shame you if you choose to drink untreated stream water—it’s to provide you with what is known from scientific research, rather than hyperbolic rhetoric. Now that you have the information, you can decide to trust in your ability to pick safe water sources, or to take precautions.

As for me, I’ll go with the instincts of the guy who studies these things. Yoder has analyzed the data, and his choice is simple: “I think that having that extra level of protection and making your water safer is worth it, because you’re trading that for more enjoyment out of the backcountry and not having to experience an illness that, at least temporarily, is pretty debilitating.”

It seems like the overwhelming majority of Slate’s twitter followers agree. (Ah, the ratio…)

Actually backpackers, you don’t need to filter stream water. Fresh water is fine to drink:

— Slate (@Slate) February 1, 2018

Continue Reading
Click to comment


The Aftermath of Michael Jackson’s Antigravity Lean

The infamous lean.

In Michael Jackson’s 1987 music video “Smooth Criminal,” the legendary performer leans forward 45 degrees from a straight-up position — and comes back. It’s a feat that seemingly defies both physics and physiology, and the move has become another element of MJ’s aura of mystery.

Some type of cinematic or mechanical trick must be responsible, since most people can manage only a 20-degree forward tilt before toppling headlong. Yet Jackson performed the move live on tours around the world for years.

Lean In

In a study published this week in the Journal of Neurosurgery, three scientists examine the so-called Antigravity Lean, not from a physics but from a physiological perspective. The three neurosurgeons, all at the Postgraduate Institute of Medical Education and Research in Chandigarh, India, combine in the article their knowledge of Jackson with data on spine biomechanics.

It’s been known for years how Jackson defied gravity. His shoes had a slot that slid onto a bolt in the floor, allowing him to perform the dramatic lean.

Bending forward is limited by the erector spinae muscles, which act like cables to support forward bends up to 20 degrees, though some dancers can achieve 30 degrees, the paper says. When near the max of a bend, you can feel the strain on the Achilles’ heel as the ankles become the fulcrum for balance. People soon return to vertical or catch themselves from falling headlong.

Though Jackson’s 45-degree bend is not physically possible without trickery, the King of Pop still needed incredible core strength and leg muscles to pull it off, the authors write. Not just anyone can lock their shoes into the floor and become Michael Jackson, it seems.

“Several MJ fans, including the authors, have tried to copy this move and failed, often injuring themselves in their endeavors,” the researchers write.

Figure A shows the Antigravity Tilt (a 45-degree forward bend) and the normal limit that most people can bend forward. Jackson used shoes with a slot that slid onto a bolt in the floor. Figure B shows the shift when the body’s fulcrum is the hip and when it’s the Achilles’ tendon. (Illustration courtesy of Manjul Tripathi)

Figure A shows the Antigravity Tilt (a 45-degree forward bend) and the normal limit that most people can bend forward. Jackson used shoes with a slot that slid onto a bolt in the floor. Figure B shows the shift when the body’s fulcrum is the hip and when it’s the Achilles’ tendon. (Illustration courtesy of Manjul Tripathi)

Tough Act to Follow

Jackson’s sleight of foot inspired generations of dancers who push the limits physically. This has resulted in spinal stresses not previously seen by neurosurgeons.

This is not to point the finger at Jackson. But it does suggest the reality that injuries can occur that might require implant spinal surgery, the article says, something potentially devastating to a dancer.

But it’s not all bad news — neurosurgeons have gained a lot of new information on how to treat spinal cord injuries in recent years, something that could be in part thanks to MJ’s envelope-pushing dance moves.

“The King of Pop has not only been an inspiration but a challenge to the medical fraternity,” Tripathi says.

Continue Reading


Your Emergency Contact Does More Than You Think

(Credit: Shutterstock)

You know when you’re filling out your medical paperwork and it asks for your emergency contact? Sure, the process might be annoying, but that emergency contact could actually be put to good use by researchers.

Since many of us use a family member, those contacts can help scientists create family trees. And they can also be used for genetics and disease research, according to a study released Thursday in Cell. Discovering what diseases are inheritable can be a laborious and expensive process — patients must be recruited and researchers must clearly determine patients’ phenotypes (physical traits that include eye color, height, and overall health and are often influenced by your genes).

To make that process easier researchers from three major New York medical centers generated family trees from millions of electronic medical records to create a database.This is the first time electronic health records have been used to trace ancestry and it’s the largest study of heritability using such records.

The More You Know

The researchers identified 7.4 million relatives with an algorithm that matched names, addresses and phone numbers from three medical centers. They found 500 inheritable phenotypes in the data just by looking at test results and observations in health records. The traits included diseases affecting skin, blood and mental health.

The data can help determine the heritability level of many common diseases. For example, researchers found that having an increase of HDL (good) cholesterol is 50 percent heritable, while LDL (bad) cholesterol is only 25 percent heritable. The study’s findings were consistent across the participating medical centers and published studies.

Previous heritability research primarily documented Caucasians of northern European descent, according to the study’s first author Fernanda Polubriaginof, but this research is much broader.

“This dataset will allow us for the first time to compute whether there are differences in other races and ethnicities,” said Polubriaginof in a news release.

Future studies could look at medical records for the hereditary contribution of any trait. Due to privacy issues, patient identifiers were removed for the data, which can only be used for research at the moment. Though, with patient consent, emergency contacts could be put to important use in the future.

Continue Reading


Mosquito Bites Leave A Lasting Impression On Our Immune System

(Credit: Kokhanchikov/Shutterstock)

Mosquito bites are like a gross form of French kissing — the insects swap your blood with their saliva, and leave a trail of salivary secretions behind like mosquito cooties. Some of those compounds prevent clotting as the insects slurp up your blood. Now researchers find mosquito spit aggravates your immune system for days afterward. The findings could help scientists develop vaccines for mosquito-born diseases like Zika.

Rebecca Rico-Hesse, a virologist at Baylor College of Medicine in Houston, Texas, wanted to know how mosquitoes exploit our immune systems with their drool. So, she and her team exposed mice with human-like immune systems to live mosquitoes. Then, they sized up the mice’s immune response as it reacted to the mosquito spittle.

The bug’s saliva toyed with their immune systems in both bone marrow and skin cells with effects that lasted up to seven days after biting, the team reports today in PLoS: Neglected Tropical Diseases. The researchers say their discovery could explain how these tissues might act as virus incubators and help spread disease.

Master Manipulators

In 2012, Rico-Hesse was looking to untangle how Dengue virus causes Dengue hemorrhagic fever — an illness that affects 400 million people each year and can lead to death — when she came across a strange occurrence. Mice infected with the virus from mosquito bites fared far worse than mice that had received an injection of the virus but hadn’t been served as a mosquito meal. The result made Rico-Hesse take a step back.

It seems that mosquito bites caused the immune system to behave differently, and in ways that could potentially give infectious diseases a leg up.

To find out, Rico-Hesse and her team set starving Aedes aegypti mosquitoes on mice that had received a dose of human stem cells to make their immune systems look more like a human’s. Each mouse endured eight mosquito bites total. Then the team checked out different parts of the immune system — blood, bone marrow, spleen, and skin cells — six and 24 hours after biting, as well as seven days later. By then, the immune system should have returned to normal.

Sneaky Viruses

Instead, the team discovered immune cells that had disappeared from the skin at least six hours post-bite came back seven days later after maturing in bone marrow, something that shouldn’t have happened. If those cells harbored a virus, they could then pass it on to new mosquitoes, who could infect others.

The research is pointing out new ways in which mosquito bites affect our immune systems, and it goes beyond simple itching and scratching.

“Mosquito saliva has evolved to modify our immune system,” Rico-Hesse said. And as their new research shows, viruses and parasites could be hijacking that activity to get to the cells they reproduce in, like bone marrow cells, faster, according to her.

Essentially, viruses might be taking advantage of the immune system’s response to travel from their point of entry — the skin — to a place they can multiply in that’s away from attacks by the immune system.

“It’s mind-blowing,” Rico-Hesse said. “No one has ever seen this before.”

Ultimately, the work could lead to infection-blocking vaccines, said Duane Gubler, an international health expert who was not involved in the research.

That’s what Rico-Hesse hopes, too. “If we can make a vaccine that would protect us against the effects of the [mosquito] saliva, or blocking our immune reaction … then we could stop global vector-born diseases,” she said.

Continue Reading