Since only 7 percent of hikers exclusively drank certified or treated water, it is likely that disease incidence can be markedly reduced by compliance with safe-water rules. Prevention City water near trails is safe to drink thanks to filtration, chlorination, and good source sanitation. He ordered that his troops drink only boiled water. This rigidly enforced order probably allowed them to escape decimating epidemics that plagued others. Untreated and possibly unsafe water is still a problem for hikers on the trail.
Filters are effective in removing all organisms except the smallest viruses.
Iodination can be effective but it makes the water taste bad. It is only recommended for emergency use, and it requires a certain amount of time, depending on the water temperature. For example, it takes at least 10 minutes in warm weather, and can take up to eight hours in cool weather. Filters I must admit that prior to picking up my Katadyn filter in Damascus I occasionally drank untreated water. I must also admit that I arrived in Damascus with backpacker's diarrhea.