This recent threat in the Adirondacks comes to us via the rivers and waterways. Giardia is ten microns in size very small: 16,000 cysts sit on a pinhead. This tiny protozoan, when injested, loges in our small intestine and causes a diarrhea virus reguiring antibiotics for a complete cure. It is best related to Mexico's "Montezuma's Revenge", but in our case, a "Marcy's Doom". It is to be avoided.