Keeping safe while visiting the parks depends on your predeparture preparations, daily routines and how you handle any dangerous situations that develop. While the potential problems can seem quite frightening, in reality most park visitors don't experience anything worse than mosquito bites or a skinned knee.

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Before You Go

Health Insurance

Review the terms of your health-insurance policy before your trip. Some policies won’t cover injuries sustained, or emergency evacuation required, as a result of ‘dangerous’ activities such as backpacking, rock climbing or mountaineering. Some policies require you to get pre-authorization for medical treatment from a call center before seeking help. Be sure to keep all receipts and documentation.


If you’re planning on doing any hiking, start getting regular physical exercise a few weeks prior to your trip. When possible, visitors from lower elevations should allow at least a day or two to acclimatize before undertaking any strenuous activity.

Medical Checklist

In addition to any prescription or over-the-counter medications you typically take, consider adding these to your first-aid kit:

  • acetaminophen/paracetamol (eg Tylenol) or aspirin
  • adhesive or paper tape
  • antibacterial ointment for cuts and abrasions
  • antidiarrhea and antinausea drugs
  • antifungal cream or powder
  • antihistamines (for hay fever and allergic reactions)
  • anti-inflammatory drugs (eg ibuprofen)
  • bandages, gauze pads and rolls
  • calamine lotion, sting-relief spray or aloe vera
  • cortisone (steroid) cream for allergic rashes
  • elasticized support bandage for knees, ankles etc
  • eye drops
  • insect repellent
  • moleskin (for blisters)
  • nonadhesive dressings
  • oral rehydration mix
  • pocketknife
  • poison-oak skin cleanser
  • scissors, safety pins, tweezers
  • sunscreen and lip balm


Yosemite National Park – Safety (

Sequoia & Kings Canyon National Park – Safety (

Wilderness Medicine Institute ( Classes, case studies and articles.

Further Reading

Backcountry First Aid and Extended Care (Buck Tilton, 2007) Inexpensive, pocket-sized wilderness-survival manual.

NOLS Wilderness Medicine (Tod Schimelpfenig, 2016) Comprehensive wilderness first-aid curriculum.

Recommended Vaccinations

No vaccinations needed.

In Yosemite & the Sierra Nevada

Availability & Cost of Health Care

For emergencies call 911. Inside the parks, cell phones often won’t work. Carrying a satellite phone or personal locator beacon is an option for backcountry trips. Park rangers with medical training can provide basic first aid, free of charge. For serious ailments, drive to the nearest hospital emergency room (ER). Hospital costs can be astronomical, especially if providers are 'out of network,' which they're bound to be. Search-and-rescue (SAR) and helicopter evacuations are only for life-threatening emergencies; they are very costly for the parks and put employees’ lives at risk.

Yosemite Area

In Yosemite Valley, Yosemite Medical Clinic is just east of Yosemite Village.

Hospitals near Yosemite:

Doctors Medical Center The nearest Level II trauma center, in the Central Valley.

John C Fremont Hospital A 24-hour emergency room, west of Yosemite.

Mammoth Hospital A 24-hour emergency room in the Eastern Sierra.

Sequoia & Kings Canyon Area

First aid is available at visitor centers and ranger stations. Hospitals nearby:

Adventist Medical Center Limited emergency services, closer to Kings Canyon.

Community Regional Medical Center The region’s Level I trauma center, west of Kings Canyon.

Kaweah Delta Medical Center A 24-hour emergency room near Sequoia's south entrance.

Eastern Sierra

Mammoth Hospital and Northern Inyo Hospital in Bishop are both full-service modern facilities.

Infectious Diseases

Amoebic Dysentery

Serious diarrhea caused by contaminated water is an increasing problem in heavily used backcountry areas. If diarrhea occurs, fluid replacement is key: drink weak black tea with a little sugar, or a soft drink allowed to go flat and 50% diluted by water.

With severe diarrhea a rehydrating solution is necessary to replace minerals and salts. Commercially available oral-rehydration salts are useful. Gut-paralyzing drugs such as diphenoxylate or loperamide can be used to bring relief from the symptoms but do not actually cure the problem.


If you drink snowmelt, stream, lake or groundwater, you risk being infected by waterborne parasites. Giardiasis is an intestinal disease marked by chronic diarrhea, abdominal cramps, bloating, fatigue and weight loss; symptoms can last for weeks. Though not usually dangerous, giardiasis requires treatment with antibiotics. To protect yourself, always boil, filter or chemically treat water before drinking. Do not even brush your teeth or rinse dirty dishes with untreated water.

Hantavirus & Plague

Hantavirus and plague are rare but serious diseases endemic to the Sierra Nevada. Hantavirus is transmitted by infected rodents through droppings, urine, saliva or blood. Plague is most commonly transmitted by the bite of infected fleas who live on plague-carrying rodents. Initial flu-like symptoms usually manifest within a week of exposure to the plague, and up to seven weeks afterward for hantavirus. If you show symptoms or suspect you were exposed, seek medical attention immediately.

Rare cases of both diseases have occurred in the parks, most recently in Yosemite. In 2012 several visitors were infected with hantavirus after staying in tent cabins in Yosemite Valley and the high country. In 2015 two visitors to the Yosemite region were diagnosed with plague. To protect yourself from infection, store all food in animal-proof containers, avoid pitching your tent near rodent habitat (eg woodpiles), use insect repellent with DEET, check for rodent droppings and avoid stirring up dust in park lodgings, and never feed or touch (alive or dead) a wild animal.

Environmental Hazards


Most people adjust to altitude within a few hours or days. Occasionally acute mountain sickness (AMS) occurs, usually at elevations greater than 8000ft. Being physically fit offers no protection, and the risk increases with faster ascents, higher altitudes and greater exertion. When traveling to high elevations, avoid overexertion, eat light meals, hydrate and abstain from alcohol and sedatives.

Initial symptoms of AMS, which is essentially the result of insufficient oxygen in the blood, may include headaches, nausea, vomiting, dizziness, weakness, shortness of breath and loss of appetite. The best treatment is descent. If symptoms are severe or don’t resolve promptly, seek medical help. AMS can be life-threatening.



Temperatures in the mountains can quickly drop from balmy to below freezing. A sudden downpour and high winds can also rapidly lower your body temperature.

Seek shelter when bad weather is unavoidable. Woolen clothing and synthetics, which retain warmth even when wet, are superior to cotton. Always carry waterproof layers and high-energy, easily digestible snacks such as chocolate or dried fruit.

Symptoms of hypothermia include exhaustion, numbness (especially in fingers and toes), shivering, stumbling, slurred speech, disorientation or confusion, dizzy spells, muscle cramps and irrational or even violent behavior.

To treat the early stages of hypothermia, get victims out of the wind or rain, remove any wet clothing and replace it with dry, insulating clothing. Give victims warm liquids (no alcohol or caffeine) and high-calorie, easily digestible food.

In advanced stages gently place victims in warm sleeping bags with heat packs or hot-water bottles (insulated to prevent burns) cocooned inside a waterproof outer wrapping. Do not rub a victim’s skin.


Frostbite refers to the freezing of extremities, including fingers, toes and nose. Signs and symptoms include a whitish or waxy cast to the skin, as well as itching, numbness and pain.

Warm the affected areas by immersion in warm (not hot) water, only until the skin becomes flushed. Frostbitten body parts should not be rubbed, and blisters should not be broken. Pain and swelling are inevitable. Seek medical attention immediately.



To prevent dehydration drink plenty of fluids (minimum one gallon per day). Eat enough salty foods – when you sweat, you lose electrolytes, too. Avoid diuretics such as caffeine and alcohol.

Because your body can only absorb about a quart (1L) of water per hour, prehydrate before starting a long hike.

Heat Exhaustion

It’s easy to forget how much fluid you are losing through perspiration while you are hiking, particularly at cooler, higher elevations or if a strong breeze is drying your skin quickly.

Symptoms of heat exhaustion include feeling weak, headache, irritability, nausea or vomiting, dizziness, muscle cramps, heavy sweating and/or cool, clammy skin and a fast, weak pulse.

Treatment involves getting out of the heat and/or sun to rest, removing clothing that retains heat (cotton is OK), cooling skin with a wet cloth and fanning continuously. Rehydrate with water, sugar drinks with a teaspoon of salt, or sports drinks. Recovery is usually rapid, though you may feel weak for days afterward.


Heatstroke is a serious, life-threatening condition that occurs when body temperature rises to dangerous levels. Symptoms come on suddenly and include weakness, nausea, hot, flushed and dry skin (sweating stops), elevated body temperature, dizziness, confusion, headaches, hyperventilation, loss of coordination and, eventually, seizures, collapse and loss of consciousness.

Seek medical help immediately. Meanwhile rapidly cool the person by getting them into the shade, removing clothes, spraying with water, covering them with a wet cloth or towel, fanning vigorously and applying ice or cold packs to the neck, armpits and groin. Give fluids if they’re conscious.


You face a greater risk from sun exposure at high elevations. Sunburn is possible on hazy or cloudy days, and even when it snows. Use sunscreen and lip moisturizer with UVA and UVB protection and an SPF of 30 or greater, and reapply throughout the day. Wear a wide-brimmed hat and sunglasses, and consider tying a bandanna around your neck for extra protection.

Tap Water

Tap water is available at all national-park facilities, including visitor centers with fountains designed to make refilling water bottles easy. All tap water in the area is drinkable.