How did Sarah Lewis unknowingly participate in the spread of cholera in the book, The Ghost Map?

In August 1854, the five-month-old daughter of Thomas and Sarah Lewis became ill. The source of her illness was unknown at the time. She had diarrhea that required a constant changing of her diapers. The soiled cloth diapers were soaked in vats of water and then washed. The wash water was disposed of in a local cesspool that fed the Broad Street pump, a source of clear water that many in the neighborhood relied upon for the drinking and cooking water. Her waste accumulated in the cesspool and bred the cholera bacteria that ultimately contaminated the water and caused the cholera outbreak.