Potential Health Problems

Knee Pain & Swelling

With every step hikers take, the weight of their backpacks comes crashing down onto their knees. Regardless of pre-hike training, nothing can prepare the knees for 6-8 hours of pounding every day for months on end. In the first month of a thru-hike, especially the first two weeks, knees swell and can become so painful and stiff you can hardly walk around.


The exact, medical prognosis of knee pain and swelling could be many things: a sprain or strain (tears of a tendon), tendinitis (inflammation triggered by overuse), Ilio-tibial band syndrome, or patellar compression syndrome (a dull, constant ache behind the kneecap).



Tendinitis, strains, and sprains are the most common problems during a hike and treatment in the field is pretty basic: stay off the leg for a few days, take it easy, eat lots of anti-inflammatory meds like ibuprofen. However, these problems can end your hike and send you home. Because of this, we prefer to focus on prevention, which is easy and requires only four things:

   1)  use trekking poles 

   2)  stretch your legs in the morning after warming up

   3)  go slow and do as low-mileage a day possible during the first two weeks 

        — long distances between water sources will make it impossible to do truly short days (6 miles, etc) 

   4)  eat ibuprofen in the evening during the first two weeks to prevent swelling overnight




Stretch every morning before leaving camp, or soon after leaving and briefly warming up. Your middle school PE coach might have taught you stretches that involve lying on the ground and bending the lower back, but don't do these. They are bad for your lower back, which will have a backpack filled with gear strapped to it all day. Instead, do these three standing stretches:


Eye Irritation

While not much of a problem as on the PCT or Florida Trail, the threat of severe dry eye and irritation confronts anyone who spends a lot of time outdoors: construction workers, landscapers, paddlers, hikers, et cetera.


It can be quite painful and the key is prevention. First, have lubricant  eye drops and use them often, before redness and irritation appear. Lubricant drops can be used while wearing contacts. Do not use Visine or similar products that contain vasoconstrictors. These constrict blood flow to the eyes and cause “rebound redness.” In other words, Visine makes the problem worse. Instead, choose brands like Refresh or Systane.



Even though the AT is a "green tunnel" there are lots of bright, sunny, exposed places where you need to wear sunglasses that block 100% of UVA & UVB rays. (Polarized lenses are nice, but they make it difficult to read LCD screens. If you plan to take lots of pictures avoid polarized lenses.)


Hypothermia doesn't just happen in sub-zero temperatures. You can get it in 60 degree weather if you are damp. Also, if you are exerting yourself (like while backpacking) and then stop hiking, your body temperature can drop rapidly. To prevent this from happening to runners after a marathon, they are wrapped in thermal blankets at the finish line.



The keys to avoiding hypothermia are staying dry and layering clothes up and down quickly, so jackets with full-length zippers are better than pull-overs.

For an in-depth review of hypothermia's symptoms, effects, treatments, et cetera, visit this page from Princeton University. I think it is important for hikers to know the symptoms for each stage of hypothermia. Page 167 of Cold: Adventures in the World's Frozen Places by Bill Streever has an incredible mnemonic device for remembering the signs of each stage:


The Umbles


   First you mumble,

   then fumble,

   then grumble,

   then stumble,

   and finally tumble.


Cotton Kills

The expression "cotton kills" has been around for decades. Do not wear cotton while backcountry hiking. Cotton is cool and comfortable against the skin, but it also dries very slowly. Because of this, when you sweat or become wet while wearing cotton, that moisture remains against your skin and draws heat from your body. Wearing cotton in damp conditions can lead to hypothermia, even in mild temperatures like the 60s.


Dead Air

The key to warmth is to make sure air does not flow across your body. You do this by trapping air in small places close to your body to create "dead air." Your body warms this unmoving dead air and it keeps you warm. So in effect, it is not the clothing that keeps you warm but the air trapped by the clothing. Unlike cotton, synthetic fibers such as fleece create dead air, even when wet, and they dry very quickly.



graphic via urinecolors.com
graphic via urinecolors.com

While completely preventable, dehydration happens anyway, usually because of laziness or impatience.


Filtering water takes time. Stopping to get water means getting to camp late. You want to keep going, to get the miles in, so you ration what you've got and don't drink as much as you should. You tell yourself you're fine and that you'll filter water in camp. You cameled-up before leaving camp that morning. It's not that hot. You're used to the heat. Just three more miles and then you'll stop for lunch. You'll get water then.



We've all been there. Fight these inclinations. Your urine should be copious and clear. If not, you aren't drinking enough water.

Heat Stroke / Hyperthermia

Hyperthermia, or the overheating of your body, advances in stages:

   1) heat cramps

   2) heat exhaustion

   3) heat stroke.


The final stage, heat stroke, will be fatal if it happens to someone on the PCT. The danger of heat stroke when in remote, rural areas cannot be overstated, so let's explore the progression of heat illness to understand how to prevent it.


1) Heat Cramps

We have all experienced heat cramps. We've all overexerted ourselves in high temperatures when playing sports, working in the yard, chasing our kids around, kayaking, or backpacking and felt the symptoms:

   1)  lots of sweating

   2)  thirst  (once you feel thirsty, you are already dehydrated)

   3)  lightheadedness

   4)  fatigue

   5)  cramps in the stomach, arms, or legs.


Treatment of heat cramps is common sense: stop what you are doing, get out of the sun, sit down and rest, and drink lots of water or Gatorade (but never beer). Trouble begins when we ignore the signs of heat cramps and push ourselves to keep going.

2) Heat Exhaustion

We bring heat exhaustion on ourselves when we do stupid things like:

   1)  assume we're used to the heat

   2)  don't want to stop having fun

   3)  get impatient and say things like, "We're almost there. Let's just keep going," or "We just

        took a break."

   4)  et cetera


Symptoms of heat exhaustion are similar to but more intense than the symptoms of heat cramps. The line between heat cramps and exhaustion is blurry, but progression from one to the next means you are dehydrated or have lost too much salt from sweating.

   1)  headache  (an early sign of dehydration)

   2)  dizziness, lightheadedness

   3)  nausea, vomiting

   4)  cool, damp skin

   5)  muscle cramps

   6)  rapid heart rate

   7)  bright spots in your vision, followed by fainting


We have fainted while playing football and vomited while mountain biking. It happens to the best of us, and when it does, you can treat it the same way you would treat heat cramps: stop what you are doing, get out of the sun, sit down and rest, and drink lots of water or Gatorade (but never beer). If possible, jump in a pool or lake, lay in a creek, take a shower, or get inside where it is air conditioned.


3) Heat Stroke

No one is too tough to get heat stroke. No one can be "used to the heat." So once you have heat exhaustion, drinking water and Gatorade is not enough. If you drink up but do not stop what you are doing and get out of the sun and heat, your core body temperature will continue to rise and you will get heat stroke, which will wreck your internal organs and possibly kill you. 


If someone faints and does not wake up moments later, they have heat stroke. Other symptoms include:

   1)  absence of sweating

   2)  hot red or flushed dry skin

   3)  tiny pupils

   4)  rapid pulse

   5)  difficulty breathing

   6)  strange behavior

   7)  hallucinations / bright lights in vision

   8)  confusion

   9)  disorientation

   10)  seizure

   11)  coma


Heat stroke happens when your core body temperature reaches 104 or 105 degrees (depending on who you talk to). It is a medical emergency. and you must go to the hospital immediately. When someone's body temperature remains at 104 or above for more than a few minutes, they enter a death zone. Their organs shut down, the brain is damaged, and they never regain consciousness.


This is why heat stroke on the PCT will almost certainly be fatal. The trail is remote, and even if you get a cell signal, an EMS team will not be able to reach your location and get the person to a hospital in time. Also, while waiting for the EMTs, you will not be able to get the person indoors, into a shower, and dump ice on them, which will save their life. The best you could hope for is dragging the person into a creek or spring.



Fortunately, heat stroke is entirely preventable.


hantavirus cases by state / image via the CDC
hantavirus cases by state / image via the CDC

Yes, hantavirus.


The presence of hantavirus on the AT seems to be a discussion many hikers don't want to have. During in-person conversations and on online forums we have experienced hikers dismissing hantavirus off-hand and refusing to admit it's present. Bill Bryson is regularly criticized for bringing it up in his book. While the risk of infection is small, unfortunately, the virus is present. Here are the facts: 


In 1993 an AT thru-hiker from Australia was diagnosed with hantavirus. The CDC concluded that "the patient's infection probably was acquired along the Appalachian Trail in Virginia." In 2012 there was an outbreak on the Appalachian Trail that caused at least one hiker to be hospitalized.


What is Hantavirus?

Hantavirus is a family of viruses found in the Americas and Asia. While the virus usually infects rats and mice it does not lead to disease in rodents. Not every variation of the virus causes disease in humans, but a few North American strains can cause a respiratory condition called Hantavirus Pulmonary Syndrome (HPS), which is fatal 38% of the time. 


Signs & Symptoms

According to the CDC, the virus's incubation time is not positively known but it appears that symptoms develop 1 to 5 weeks after exposure to fresh urine, droppings, or saliva of infected rodents. Universal early symptoms include fever and muscle aches in the thighs, hips, back, and shoulders. Half of infected people experience headaches, dizziness, chills, nausea, vomiting, diarrhea, and abdominal pain.  As the disease progresses the lungs fill with fluid. 



The virus appears in rodent urine, droppings, and saliva. However, the exact details of transmission to humans have not been discovered. Some researchers suspect you can get the virus by eating food contaminated with urine, droppings, or saliva or by touching a contaminated surface and then touching your nose or mouth.


What is certain is that HPS is a respiratory disease, and infection will  take place if the virus is inhaled, which can happen when fresh rodent urine, droppings, or nesting materials become airborne, say by someone sweeping out a shelter. Fortunately, hantavirus is not  transmitted between people, like when touching or kissing. 


Likelihood of Infection on the AT

It’s greater than on any other American long-distance trail. While hantavirus is native to the American West, the absence of AT-like shelters on the PCT and CDT means hikers do not congregate in large groups at single locations where their crumbs and trash feed populations of mice and rats.


On the AT however, shelters provide rodents with a place to live and attract people who support rodent populations with their crumbs. Additionally, hikers sleep in shelters where rodents feed, nest, and defecate.


What To Do


There has not been a reported hantavirus outbreak since 2012 but if you are concerned about the virus, it's best not to sleep in the shelters. Sleep in your tent instead. Ultimately the solution to the hantavirus problem won’t be found in changing the behaviors or individual hikers. The ATC needs to co-ordinate a sustain large-scale rodent population control effort at all shelters, and shelters must be kept immaculately clean.

Water-Born Illnesses

Water sources on the AT may contain bacteria, cysts, and parasites like fecal coliform bacteria and giardia. These illnesses are discussed on the water treatment page.

Ass-to-Mouth Disease

You are your own biggest health-hazard in the backcountry. Outdoor novices worry about poison ivy, snakes et cetera, but if you get sick in the backcountry, you probably did it to yourself through poor hygiene. Tips for keeping clean are discussed on the sanitation page.

Insect-Born Illnesses

Mosquitoes and ticks are vectors for diseases that are discussed on the insects page.