Disease transmission from contaminated water occurs principally by ingesting water. The major organisms of concern are parasites such as Giardia and Cryptosporidium, and bacteria such as Shigella and E. coli. These organisms primarily affect the gastrointestinal system, causing diarrhea, abdominal cramps, nausea, and vomiting with or without fever. Most of these illnesses are not usually serious or life-threatening, except in the elderly or those immunocompromised. If your hands have touched contaminated water, keep them away from your face. You shouldn't eat, smoke, or wipe your face until you have washed your hands in sanitary water. Disease organisms from contaminated water can enter your body orally.