Giardia

Giardiasis is a waterborne intestinal illness caused by the microscopic parasite Giardia lamblia, commonly contracted by hikers and campers who drink untreated water from streams, lakes, or springs. The infection causes severe diarrhea, stomach cramps, nausea, and dehydration that can last for weeks if untreated. This is why outdoor enthusiasts must always purify, filter, or boil water from natural sources before drinking, even in seemingly pristine wilderness areas. Giardiasis is one of the most common reasons backpackers and hikers become seriously ill on multi-day trips.

Cryptosporidium is a microscopic parasite commonly found in natural water sources like streams, lakes, and rivers that can cause severe gastrointestinal illness in hikers and campers. This waterborne pathogen is particularly concerning for outdoor enthusiasts because it's resistant to standard water treatment methods like iodine and chlorine tablets. Symptoms include diarrhea, stomach cramps, and dehydration, which can be especially dangerous in backcountry settings. To protect against Cryptosporidium, campers should use water filtration systems with pore sizes smaller than 1 micron or boil water for at least one minute before consumption.