You could if you used the Lifestraw, a $3.00 personal water filtration device.  This filter was created for those in rural areas without access to clean water, and it removes waterborne diseases including 99.9% of bacteria and 98.7% of viruses for every 700 liters (app. 185 gallons) of water. It will filter bacteria like Cholera or viruses like Parvovirus. But it will not filter heavy metals or parasites like Giardia. See Treehugger for a brief description of this invention or the Lifestraw website for more detailed information. And try not to forget to check out this super blog post on the same issue.