Giardia is passed in the feces of an infected person or animal and may contaminate water or food. The disease can spread from person to person in day care centers or other settings where people sometimes don't wash their hands well enough. People who go camping or hunting can get Giardia by,drinking untreated water. People with Giardia may experience mild or severe diarrhea, stomach cramps, bloating and fatigue. Diarrhea may last several weeks or months and might cause weight loss.
Fever is rare.
However, some people infected with Giardia do not become ill. Many young children have no symptoms. Diarrhea usually begins within 10 days, but it can begin as early as 5 days or as late as 25 days after infection with Giardia. An infected person can spread Giardia for a few weeks to a few months. Treatment may shorten this length of time.