Symptoms can last anywhere from a few days to months. Warm blooded animals, such as elk, deer, muskrats, beavers, domestic or farm animals, and humans can be hosts for this protozoan. Giardia is excreted into the environment from the fecal material of the warm blooded hosts. It is then washed into lakes, rivers, and streams. For this reason, consumption of untreated water while hiking, camping or at any time is not recommended.
Travelers often contract giardiasis in foreign countries, as well.
Seattle Public Utilities provides continuous disinfection and monitoring of it's water supplies to demonstrate that effective treatment is being carried out.