Dr. Metcalf has always considered the gold standard of microbe inactivation procedures to be: Will the person recommending a specific procedure actually drink heavily contaminated water which has been treated by the particular method? Dr. Metcalf will, and has many times, with solar water pasteurization using a CooKit and a WAPI. Certainly the folded sari method is dangerous. The SODIS method is effective at reducing viable bacteria. However, its ability to inactivate viruses, particularly the dangerous rotavirus, is less certain. And there is no inexpensive, easy device that indicates when SODIS-processed water is safe to drink.