On September 8, 1854, acting on the advice of Dr. John Snow, London municipal authorities removed the pump handle from the Broad Street well in an effort to halt a major outbreak of cholera. Although an anesthesiologist by profession, Snow had methodically mapped the homes of new cases of cholera. He found that many clustered around the Broad Street pump.
Snow’s findings, still regarded as a classic example of epidemiology, established the principle: “that the most important information to have about any communicable disease is its mode of communication.” Dr. Snow did not establish the biologic mechanism of cholera or devise an effective treatment for those stricken with the disease; instead, his research indicated that the disease was transmitted through contaminated water. His methods demonstrated how the root cause of an emerging public health problem could be determined through epidemiological observation. It was later determined that a cholera-contaminated diaper had been washed near the pump.