John Snow, M.D., March 15, 1813-June 16, 1858, was a British physician and a leader in the adoption of anesthesia and medical hygiene. He is considered to be one of the fathers of epidemiology, because of his work in tracing the source of a cholera outbreak in Soho, England, in 1854. He  published On the Mode of Communication of Cholera  in 1849. His work, along with that of William Farr, prevented major new cholera epidemics in London in the post 1860’s period.