Giardia is a microscopic parasite that can cause gastrointestinal infections in humans and animals. Synonyms for giardia include giardiasis, beaver fever, traveler's diarrhea, and contagious diarrhea. Giardiasis is the clinical term used to describe the intestinal infection caused by this parasite, while beaver fever is named after the animal that is often associated with the transmission of giardia. Traveler's diarrhea is a common term used to describe diarrhea that is acquired while traveling to different parts of the world, and giardia is one of the common causes. Contagious diarrhea refers to the possibility of giardia being transmitted from person to person, especially in daycare centers and other communal settings.