E. coli is brought into the creeks from sewer overflows during heavy rains, or malfunctioning sewage systems. It can also be in the feces from animals using the creek for wading, drinking and cooling.
E. coli in large amounts can indicate presence of pathogens such as typhoid, cholera, or hepatitis A. Ingestion of E. coli can lead to gastrointestinal distress and eye, nose, and throat infections.