John Snow was a British physician and is considered to be the father of modern epidemiology. He is famous for his investigations into the causes of the 19th century cholera epidemic in Soho. He noticed that significantly higher deaths were recorded in households that frequently used the Broad Street pump for water. He used a spot map to illustrate how the cases of cholera were clustered around the pump. Snow then attempted to clean the water using chlorine, and removed the handle on the pump, so no-one could use it. Later, it was discovered that the well had been dug only three feet from an old cesspit (a pit covered in cistern, used to dispose of urine and feces), which was leaking fecal bacteria.
