All it takes is ONE microscopic Giardia Cyst Egg to be Swallowed into your Stomach and then your GUTS, .....and then Walla ....in a couple days...instant HOT GUSHING Liquids out the Back door and up the front Door. All it takes is ONE CYST . Any system can have a Horrendous and Painful - Contaminating Transference . In English....this Means..... Explosive Diarrhea , Major League Headache , and Straight Stream Vomiting. This means Weight Loss , as in Now , For Days . Until the Doctor gives you the Bottle of Magic Pills. So perform Water Purification.. Very Carefully . Other wise they will call you the Mighty ... " TWO STEP " .... Cheers ! GST