Question: Flooding after two weeks of heavy rainfall in Tooele, Utah preceded a high rate of diarrheal illness. Giardia lamblia was isolated from 25% of the patients. A comparison study of a town 65 miles away revealed diarrheal illness in 2.9% of the people interviewed. Tooele has a municipal water system and a municipal sewage treatment plant. Based on the information provided, what is the probable cause of this outbreak of diarrhea in Tooele? What other possible causes are supported by these same facts? What method(s) could be used to stop the current outbreak and prevent future outbreaks?