Bears, Noro, and Lyme: What to Worry About (or not) on Your Thru-Hike

So, you’re planning to head out on trail for a long walk. Maybe even a thru-hike of one of the Triple Crown trails — the Appalachian Trail, Pacific Crest Trail, and Continental Divide Trail.

You’ve probably gotten a lot of questions from people who think you are out of your mind, many of which begin with, “Aren’t you afraid of…”

Veteran thru-hikers will tell you that while there are inevitable dangers on trail, stereotypical fears are usually overblown. Here’s a hard look at three common concerns on the trail—bears, Lyme disease and norovirus—how much you should (or shouldn’t) worry about them, and how to minimize their impact on your hike.



Let’s start with the bugaboo that friends and family fret about when they imagine you—a tasty human hors d’oeuvreout in the wild for six months.

Bears are a fact of life on all three Triple Crown trails. The American black bear (Ursus americanus) is common on all three trails, while the brown bear, aka grizzly (Ursus arctos) is found only near the northern reaches of the CDT. If you see a polar bear, Ursus marinus, you’re either taking a zero in a city with a zoo or considerably off course.

Grizzlies and black bears were once hunted to near extinction. Today they are thriving, with as many as 465,000 black bears and 200,000 grizzlies (mostly in Canada and Alaska) roaming the continent.

So, how dangerous are they? Here’s a clue: Most long-distance hikers consider bear sightings a highlight, not a nightmare. Consider these stats:

  • Between 2000 and 2019, there have been just 53 documented fatal attacks on humans by bears in North America, or about 2.8 per year.
  • Of those, just ten fatal grizzly attacks and 10 fatal black-bear attacks occurred in the Lower 48, or about one per year.
  • No fatal grizzly attacks occurred in states traversed by the AT; one occurred in a PCT state (California, but with this notable asterisk: a captive bear killed its handler); nine were in CDT states.
  • Of CDT-state grizzly attacks, six occurred in Yellowstone National Park (around four million annual visitors) or Grand Teton National Park (around three million annual visitors).
  • Of fatal black-bear attacks, four occurred in AT states, two were in CDT states, and none were in PCT states.
  • No fatal black-bear attacks occurred on the AT, PCT, or CDT. The two CDT-state black-bear attacks occurred far from the trail. Of the AT-state attacks, two occurred about ten miles from the trail (one in the Smokies; the other was the first recorded bear fatality in New Jersey history); the other two were at least 50 miles from the trail.

There is no reliable data on nonfatal attacks on or near Triple Crown trails. But considering the millions of people who annually visit some part of the trails — the Appalachian Trail Conservancy estimates that more than two million people visit the trail every year, for example, and some seven million people a year visit Yellowstone and Grand Teton national parks, traversed by the CDT — your chances of a dangerous bear encounter are vanishingly small, considerably less than one in a million. Statistically speaking, you’re about 60,000 times more likely to be killed by a human than a bear.

That said, it pays to be bear-smart.

  • The ATC now recommends that hikers carry food in a bear-resistant container approved by the International Grizzly Bear Committee. Canisters are required on significant portions of the PCT and CDT.
  • Learn how to properly hang a bear-bag. (Dangling a non-bear-proof bag from a spindly limb four feet from the ground does not count.)
  • Prepare and eat food away from your sleeping quarters.
  • Keep your dog in check. One study of black-bear attacks found that more than half involved an off-leash dog.
  • Educate yourself of how to respond if a bear does attack.

Conclusion: Be bear-smart, but your chances of having a negative encounter with a bear are extremely low, bordering on non-existent.

Lyme disease

If you are a CDT or PCT hiker, you’re mostly off the hook for this one, as incidence of Lyme disease is negligible in the West (though it is rising faster in California than in any other state except Florida).

But if you are an AT hiker, Lyme disease should concern you much more than bears. Believe it or not, one out of every 20 AT thru-hikers will contract this tickborne disease in 2019.

In fact, the AT passes through ten of the 15 states with the highest Lyme incidence (cases per 100,000 residents), according to 2017 statistics compiled by the Centers for Disease Control. The worst state may surprise you: Maine, with 1,850 cases, or 106 per 100,000 residents. But number three Pennsylvania is tops in raw numbers, with a whopping 11,900 cases, more than twice as many as the next two contenders, number 13 New York (5,155 cases) and number seven New Jersey (5,092). These AT states also rank in the top 15 for cases per 100,000 residents: number two, Vermont (1,092 cases); number five, New Hampshire (1,381); number six, Connecticut (2,051); number 11, Maryland (1,891); number 12, Massachusetts (410); and number 14, Virginia (1,657). Lyme disease is considerably less common in southern AT states so far — in 2017, 45th-ranked Georgia reported just 0.1 cases per 100,000 residents; Tennessee (0.2) was 42nd, and North Carolina (0.7) was 26th — but bites from the lone-star tick, Amblyomma americanum, can cause STARI, or southern tick-associated rash illness, which can cause similar symptoms.

cdc lyme disease appalachian trail

lyme disease appalachian trail

Possible erythra migrans rash, taken in emergency room in Reading, PA.  Clay Bonnyman Evans photo.

If caught early, Lyme disease is easily treated with common antibiotics such as Doxycycline and Amoxicillin. If left untreated, Lyme can cause serious, even life-threatening symptoms, including heart disease and partial paralysis. You do not want to mess around with Lyme.

But here’s the catch: the disease cannot be definitively diagnosed, even through laboratory tests, for up to six weeks.

“Antibodies against Lyme disease bacteria usually take a few weeks to develop,” according to the CDC. “During the first few weeks of infection, such as when a patient has an erythema migrans rash, the test is expected to be negative.”

Another bummer: The ticks most likely to transmit the disease are in the nymphal stage. They are teeny-tiny little pests, the size of a poppy seed or even smaller. Hard to find.

But don’t worry: Doctors in Lyme-endemic states are hip to all this. Rejected by a doc-in-a-box clinic because my fever was “too high” (104 degrees), I staggered into an emergency room in Reading, PA, during my 2016 AT thru-hike. There, the no-nonsense doc swiftly prescribed doxycycline based on a) my symptoms (including a non-bulls-eye rash) and b) circumstances, i.e., living in the woods and infrequently showering. It sucked, but after a few days of misery, I was on my way north.

You may have heard stories of a debilitating, ongoing illness called “chronic Lyme disease.” The CDC is skeptical of this alleged diagnosis, preferring the label “Post-Treatment Lyme Disease Syndrome.” The agency cautions that some treatments prescribed by doctors for the syndrome, including prolonged courses of antibiotics, are not effective and can cause long-term complications.

Your best bet, of course, is to avoid contracting Lyme (or STARI) in the first place. Here are a few good rules recommended by the ATC.

  • Wear clothes treated with permethrin. You can buy pre-treated clothes, spray them yourself or even send your gear to be treated by a company called Insect Shield.
  • Wear long pants and sleeves in tick territory. (Confession: Even after suffering the symptoms of Lyme, I couldn’t bear wearing long sleeves and pants while trudging through the mid-Atlantic inferno in high summer.)
  • Wear light-colored clothing.
  • Apply Deet-based insect repellent to exposed skin.
  • Do tick checks nightly. Recruit a pal to check, uh, the areas you can’t see yourself; make sure he or she is a really good pal, since the tiny nymphal ticks most likely to transmit Lyme are very hard to see.
  • Ask your doctor if she will prescribe a course of doxycycline or Amoxicillin prior to your hike. If you develop flu-like symptoms, take the antibiotics as prescribed, and you’ll save yourself the hassle and cost of going to a doctor who will simply prescribe the same medication.

Conclusion: Lyme-bearing ticks are be a lot smaller than a bear—800 million times smaller—but they should take up much more of your concern.


This nasty little bug is millions of times smaller than a tick, but it frequently causes distress and suffering among long-distance hikers.

Noro, as it is often referred to, is a tiny viral particle that causes diarrhea and vomiting. The most common cause of acute gastroenteritis in the United States, noro annually causes up to 71,000 hospitalizations and 800 deaths. It’s a tenacious little bugger that can survive on a dry surface for weeks.

There aren’t good statistics about the incidence of noro on trails — but the ATC typically puts out several noro warnings each year for AT hikers. It’s a people thing: the more crowded the trail, the more likely it is that the disease will be present. Suffice it to say that it’s common, and all-too-easy to contract by:

  • Having direct contact with an infected person.
  • Consuming contaminated food or water.
  • Touching contaminated surfaces, or consuming food that has touched contaminated surfaces.
  • “You can get norovirus,” according to the CDC, “by accidentally getting tiny particles of poop or vomit from an infected person in your mouth.” Yum.

Symptoms usually develop 12 to 48 hours after exposure and the illness usually runs its course in one to three days. Disturbingly, people may continue to “shed” the virus for up to two weeks.


 Instead of gross illustrations of norovirus, here’s a shot looking up from the bottom of Mahoosuc Notch in Maine.  Clay Bonnyman Evans.

It’s hard not to be filthy on trail — it’s part of the fun, right? But there are plenty of things you can do to reduce the likelihood of contracting a nasty case of noro on the trail.

  • Wash your hands, early and often. With soap and water (at least 200 feet from any water source). Antibacterial hand sanitizer isn’t as good as washing, but it’s better than nothing.
  • Don’t share food, water bottles or utensils.
  • Don’t shake hands. Fist bumps are not just an affectation!
  • Properly treat water.
  • Follow Leave No Trace guidelines for disposal of human waste.
  • Report outbreaks or incidence of norovirus. Email to help the ATC notify hikers of outbreaks.

Conclusion: Norovirus is small—millions of times smaller than a bear or tick—but it’s brutal, and can cause miserable havoc on trail. You have a right to be worried about it, and don’t forget to wash your hands!



A few corrections regarding the Lyme section:

  1. You are never “off the hook” with tick-borne illness.  Maps showing the locations of ticks have been used against patients for decades – and they are constantly changing due to migrating birds depositing them everywhere:  Plus, there are many other pathogens you should be worried about besides Lyme: (BTW:  the actual number is 18 and counting)
  2. As you read the paragraph based on CDC numbers of infected people, please remember these are notoriously low.  The actual numbers are frightening and it’s only getting worse.  Lyme/MSIDS is a true pandemic, showing no signs of slowing down.
  3. Regarding STARI – it looks, smells, and feels exactly like Lyme so don’t think it’s a walk in the park.  Shenanigans abound when it comes to the South and tick-borne illness.  For more on that debacle:,
  4. I’m not sure what “Lyme is a very specific disease” means to this author but it is as vast and wide as you can imagine with symptoms all over the place. It’s unbelievable and had I not lived this nightmare on steroids, I probably wouldn’t believe it myself.  And rarely does Lyme come alone: For the first time, Garg et al. show a 85% probability for multiple infections including not only tick-borne pathogens but also opportunistic microbes such as EBV and other viruses.  Do you call that a “specific disease?”  It sounds like a pathogen storm to me. This issue complicates cases exponentially and necessitates different medications.  The few minor symptoms they mention are far from the picture of Lyme/MSIDS.  This is probably the most complex illness known to man.
  5. The percentages given for the EM rash are highly inflated.  In the first ever patient sample in Lyme, Connecticut only a quarter had the rash 1976circularletterpdf.  Then there’s this, showing a wide range (27-80%) depending on who’s counting:  I hardly call that completed and accepted science, yet they throw that number out ALL the time as if Moses etched it on stone tablets.
  6. While everyone claims Lyme is “easily treated” with common antibiotics, I’m concerned the CDC’s recommended mono-therapy of doxycycline is setting people up for potential Alzheimer’s, dementia, and other neurological diseases later:,  Until they acknowledge that borrelia is pleomorphic, this fact remains in the dark about the importance of addressing ALL forms of Bb in treatment.  Doxy doesn’t do that.  To demonstrate treatment complexity, please see:
  7. His statement, “But don’t worry: Doctors in Lyme-endemic states are hip to all this,” is completely ignorant.  Lyme/MSIDS is in a desperate state of affairs and until much change occurs, do not head to a mainstream doctor if you become infected.  You need an experienced practitioner trained by ILADS for this:  Mainstream doctors will treat you with the antiquated and unscientific guidelines of 21 days of doxycycline, which has been proven over, and over again NOT to work.
  8. The CDC can be “skeptical” all they want, but there are numerous subsets of folks that remain ill:  Suffice it to say the science remains unsettled but people are suffering.  As to prolonged courses of antibiotics not being effective and causing long-term complications, I would probably be dead without them and I’m sure many, many others would say the same. This IDSA founder from Wisconsin used 6-8 grams of IV antibiotics for 6 weeks and longer if they required it. Interestingly, Dr. Waisbren stated, “Back in the 1950’s, when many of these drugs were first coming out, infectious disease doctors studied and used them widely. We would put children with rheumatic fever on penicillin for twenty years or more to prevent strep throat and it (the penicillin) did not hurt them. Trust me when I say that nobody in Lymeland wants to be on antibiotics. Treatment is hard, painful, and expensive.  We are on them because despite what the CDC states, they work better than anything else at present, and compared to most other treatments are affordable.