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Deadly Threats You Never Heard of Lurk in Our National Parks


Some deadly diseases you’ve never heard of lurk in our national parks. It's extremely unlikely that you'll ever be infected, but the odds are not zero. And if you are among of the unfortunate few, may the Good Lord have mercy on you.

If you are visiting or working in a western park and you are messing around in a backcountry cabin or other structure that gets closed up for lengthy periods (all winter, for example), for heavens sake don’t stir up the dust and breathe it. And if you soak in a backcountry hot spring while visiting a national park – the hot springs at Yellowstone and Death Valley’s Saline Valley leap to mind – think twice before you duck your head under water or allow water to be splashed into your nose. Inhaling a noseful of sealed-cabin dust or a few drops of hot springs water isn’t just unpleasant. There’s a credible chance it might kill you.

On March 25, 2004, Glacier National Park Deputy Superintendent Jerry O’Neal died after contracting hantavirus pulmonary syndrome (HPS). There is no evidence that he contracted the illness while performing his duties at Glacier, but he did become infected with HPS in that area,quite possibly at his home.  

HPS is extremely dangerous. There is no effective treatment for it, and about half of the victims die.

HPS, which was first recognized in the Four Corners area of the southwestern U.S. in 1993, is a type of hemorrhagic fever transmitted to humans primarily via inhalation of airborne dust containing infected rodent droppings. The disease, which begins with flu-like symptoms, can also be transmitted by ingesting contaminated dust, such as the dust that accumulates on the lids of canned soft drinks and foods. It can also be transmitted through contact with the saliva of an infected rodent.

While campers and hikers are at some risk of HPS (the virus lurks in the duff on the forest floor and other places with rodent droppings), the greatest threat is to park workers involved in the seasonal opening and cleaning of park structures in the western states. If the workers performing such duties want to stay healthy, they must use effective respiratory protection (!!). Park workers who poo-poo this precaution and refuse to wear respirators are rolling the dice with the devil.

Hantivirus is not as rare as you might think. The Centers for Disease Control and Prevention (CDC) reported that rodents (rats and mice) carrying hantavirus have been found in at least 20 national parks, and there is good reason to believe that they’re present in nearly all of the national parks. The empirical data support the conclusion. Rodents carrying hantivirus have already been reported in every single western state and in many eastern states as well.

Danger lurks in national park waters, too. A very nasty amoeba, the Naegleria fowleri, occurs naturally in bodies of warm fresh water. While it is found in some lakes, it is especially found in warm or hot springs – places where, given acceptable temperatures, visitors might reasonably choose to bide a while and soak. Warm water to ease your aches and pains at the end of a long day’s hike. Warm water to soothe your worries away. Warm water to cleanse and rejuvenate you. Aaaaaaaaaah!

The thing is, you don’t want that water to get into your nose. If you duck your head, or perhaps get water splashed into you nose, you might inhale a few drops of that water. And then, just possibly, you could be in very deep trouble. The water could have Naegleria fowleri in it.

The Naegleria fowler amoeba, which is sometimes called the “brain-eating amoeba,” is very dangerous (to put it mildly). It typically enters the body through the nasal passages, then attacks brain tissue. The results are usually catastrophic. There were 33 cases of Naegleria fowleri infection recorded between 1998 and 2007, and 32 of the victims (including all six infected in 2007) died. That’s a mortality rate of 97 percent. You’d have a better chance of surviving a bullet wound in your chest.

Research has established that this nasty amoeba very probably inhabits a lot of warm water sources in our national parks. A study that Montana State University researchers conducted in 2003 found it in nearly two dozen hot springs sampled in Yellowstone and Grand Teton. It is almost certainly present in hundreds and hundreds of pools and lakes that have not yet been tested.

The bottom line is that a park visitor who soaks in a warm spring would be foolish to assume that there are no Naegleria fowleri in the water. That being the case, warm water bathers should avoid ducking their heads in the water or splashing water in their noses.

Postscript: You need to be aware of the risk of plague in western parks as well. Transmitted primarily by the bites of fleas from infected rodents, plague is known to occur in parts of California, Utah, Arizona, Nevada, and New Mexico. The three most common forms of plague are bubonic plague (infects the lymph nodes), pneumonic plague (infects the lungs), and septicemic plague (infects the blood). Don’t contract plague if you can help it. Your chances of surviving bubonic plague are about fifty percent. Pneumonic plague is even more dangerous. You’ll probably live if it’s treated (only 5% mortality), but if it isn’t properly diagnosed and treated, your chances of survival are very close to zero.


What a story. I have enjoyed the warm springs in Saline Valley over the course of three days and broke all of the rules of safety as did others with me. Suppose we were lucky. Hope there are signs posted now. Beautiful area and aside from a few people that like to play their stereo full blast, it was very nice. Think signs would be out of place? I know the loud music was.

Geez, Bob, are you trying to take all the fun away from a park visit?

As for plague, we shouldn't forget that it killed an NPS wildlife biologist in Grand Canyon National Park in 2007.

Other threats, though not disease-related, include altitude sickness (aka acute mountain sickness) that can strike if you head above 8,000 feet and are not acclimated; heat stroke or heat exhaustion, which are very common in the Grand Canyon during the summer months; hypothermia, which can occur in many parks if you're not careful, and; various nasty intestinal ailments that are common to Colorado River rafting parties.

All that said (and I'm sure we missed some threats), I wouldn't let any of these keep me out of the parks.

I agree that none of these perils should discourage visits to parks, but they are a good reminder that prudent measures are a good idea - for visitors and employees.

This article also brought to mind a humorous personal experience (although it probably didn't seem so at the time):

Back in the 1980s, I worked in the Big Thicket National Preserve in Texas, and the park staff agreed to participate in a study by the state Health Department to try to determine if ticks in the area were carriers for Rocky Mountain spotted fever. I can testify from personal experience that the thickets of southeast Texas qualify as critical habitat for both ticks and chiggers, so the park staff also provided a pretty good test group for effective repellents against those critters.

For several months, when we went to the "field" we were armed with a set of small glass vials and some official Texas Dept. of Health labels. If we found a tick on our person, we collected it, put it in the vial, secured the lid, and completed a stick-on label with details (was the tick attached to us or merely crawling, date and location, etc.) The bottled ticks were then shipped off to the lab, where they presumably gave their lives for the sake of science.

One afternoon, the Chief Ranger called me into his office near the end of the day, and a rather unusual conversation ensued. After some preliminary small talk, the short version went something like this:

Chief: "So, how are you feeling today?"

Ranger J (who has just returned from a delightful day in the woods and swamps, where the readings for both humidity and heat exceeded "90"): "Okay."

Chief: "Any unusual medical problems lately?"

Ranger J: (Increasingly puzzled): Nope.

Chief: (after a bit more beating around the bush): "Well, I just thought I should let you know three of the last four ticks you sent in came back positive for Rocky Mountain Spotted Fever."

Ah, the joys of rangering!

As a follow-up, my personal experience was that powdered sulphur, applied topically as a dusting powder, was the best anti-tick measure. The military-issue insect repellent, which contained something like 95% DEET as the active ingredient, was also fairly effective, but since it melted plastic camera lens caps and water bottles, super DEET fell out of favor as a classic case of the preventive being worse than the threat.

Fortunately with the new rule changes regarding guns in the park, I'll just blast those little amoebas to peices!

Better bring lots of ammo, Hobblefoot. Naegleria fowler is a single-cell organism and kinda on the small side.

I'm curious - are there other "gotcha's" one should worry about in the northern parks / states? The Isle Royale National Park (Island) in Michigan has had an ongoing wolf / moose - predator/prey study that has been going on for 50 years (as of 2008). There is a good possibility that I will be working in the study this May (the park is only open from May - September), and probably a good chance that I will be the first to open up some cabins, sheds and other enclosures that are closed from October to April. Recommended protocol? There is obviously a rodent population in every single state, in all environments - that goes without saying - yes?

Being a native Texan, your comments on Rocky Mountain Spotted fever and the use of powdered sulfur as a deterrent are not lost. My youth was spent crawling around on the forest / plains floors, hiding in piles of leaves during paint ball matches, crouching behind blinds for hours while hunting and waiting for that one 'shot' while photographing. I figure that from what yall depict, me and all my buddies probably should be dead by now (40+ years.. be nice). In all sincerity, it's timely information at any age - wish we had known back then what we know now. Also - don't forget that ticks also carry Lyme's (sp) disease and a few other rarer ones. You can bet - if you catch sickness from a tick / flea bite, it won't be a pleasant ordeal.

Lastly - while I've never heard of someone getting sick from a chigger bite, there has been many a night spent trying everything (smothering them with nail polish on your skin at the bite/entry area, clawing at them, ripping your skin off, etc...) to get rid of the darn things. They are a bane to all Texans - in all areas.

Bill, I've got a story about the Saline Valley hot springs in the works, and if I can clear some of this backlog I'll finish it and post it in the near future. Meanwhile, I've never heard of anyone being harmed by infectious disease lurking in the water there. Your signage suggestion put a smile on my face. I'd guess that the typical Saline Valley bather has about as much use for a warning sign as he has for a swimsuit.

Tom, I'm afraid I'm not familiar with the disease threats at Isle Royale. I trust that you've already thought of directing your questions to the park superintendent and your research program manager(s). They ought to feel some sense of obligation in this matter. BTW, when I read Nevada Barr's most recent book Winter Study, the novel that has super ranger Anna Pigeon working with the ISRO wolf study program, I noticed that a whole bunch of scientists were listed in the books credits section. It's a good bet that somebody on that list is a goldmine of information you can use.

Your query puts me in mind of an event that happened in July 1963. I was then an undergraduate student assistant (free lodging and tuition) at a six-week geology field camp based at an old CCC camp on a lake WAY back in the Seney Swamp in Michigan's Upper Peninsula. (Serious fans of Ernest Hemingway will recognize this as the the Big Two-Hearted River setting for one of Hemingway's lesser known productions -- the one that has protagonist Nick Adams in need of wilderness retreat and soul-healing.) Anyway, we students and the professor in charge opened the big old CCC-built lodge after it had been sitting unused for goodness knows how long. In addition to the mummified porcupine we found in the chimney, there was an incredible number of very live mice scurrying around. That evening we sat around the big kitchen table, drank Pabst Blue Ribbon (Lloyd Schmaltz was a very live-and-let-live professor) and amused ourselves by setting mousetraps for these rodents -- the very rodents whose droppings we had swept out of the huge lodge earlier that day. Mouse after mouse after mouse would pop into view, head for the nearest cheese-baited trap, and BAM! -- the trap, a newly dead mouse in its lethal embrace, would fly into the air accompanied by cheers that grew louder and louder as the evening progressed and our beer supply diminished. We could have repeated the exercise out in the shed where a similar colony of rodents was ensconced. I remember coughing every morning at dawn when I went out to the shed to start the diesel generator that powered the lodge's electrical system. This was an incredibly dusty environment, and I have no doubt that my deep coughs drew a good deal of powdered rodent crap deep into my lungs. Forty-five plus years down the road, I am left to assume that either the dust was not contaminated by hantivirus or my immune system is better than average.

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