After studying previous outbreaks, physician John Snow drew the conclusion that cholera was a water-borne disease. When the 1854 broke out, Snow mapped the locations of the cases in Soho, London, and found that they centered around a well he deemed contaminated. He asked that the pump's handle be replaced, after which the epidemic petered out. Snow also discovered that households whose water supplies came from companies that used the Thames downstream, after many sewers had flown into the river, were fourteen times more likely to die from cholera. He thus recommended boiling water before use.