Human or animal feces ...

Human or animal feces infected with E. coli sometimes get into lakes, pools, and water supplies. People can become infected when a contaminated city or town water supply has not been properly treated with chlorine or when people accidentally swallow contaminated water while swimming in a lake, pool, or irrigation canal.The bacteria can also spread from one person to another, usually when an infected person does not wash his or her hands well after a bowel movement. E. coli can spread from an infected person's hands to other people or to objects.