There is no way of telling just by looking at the water whether giardia is present. Giardiasis is not usually life threatening. Disease symptoms often include diarrhea, increased gas, loss of appetite, abdominal cramps, and bloating. Weight loss may occur from nausea and loss of appetite. Discomfort may first appear within a few days after ingestion of giardia, but may last as long as six weeks.
Most people are unaware they have been infected until they return home from vacation.
If not treated, symptoms may disappear on their own, only to recur intermittently over a period of many months. If you begin to show symptoms of Giardiasis after drinking untreated water, you should inform your doctor. With proper diagnosis the disease is curable with appropriate prescribed medicine. Boiling will also destroy other organisms causing waterborne disease. Although chemical disinfectants such as iodine or chlorine tablets work well against most waterborne bacteria and viruses that cause disease, they are not yet considered as reliable as heat in killing giardia.