John Snow

• In 1831, Dr John Snow fought a cholera outbreak in Killingworth colliery, Newcastle. This made him convinced that cholera was a water-borne disease, but few agreed with him. This was because of the miasmic theory.
• During the 3rd cholera outbreak, Snow was working as a general practitioner in Frith Street in Soho, London. His suspicions fell on a pump in Broad Street, known locally for its taste and purity. Once Snow persuaded the authorities to lock the pump handle, the number of deaths fell dramatically.
• To connect the falling death rate with the closing of the pump, Snow used geographical epidemiology to create a meticulous study of the area. Using careful observation, house-to-house interviews and meticulous research, he constructed a detailed picture of the cholera epidemic.
• Snow supported his theory with anecdotal evidence, such as:

  • Seven workmen who lived outside the area but were working around Broad Street and drinking from the pump died.
  • 535 people lived in the local workhouse close to the pump, yet got their water from another source. Only 5 inmates died.
  • A widow who used to live in the area had a large bottle of water from the pump delivered to her Hampstead home died, yet none of her neighbours caught the disease.
  • 200 people worked in the local factory and got water from the pump. 18 workers died.
• A large study done by John Simon, the medical officer of health for the City of London, covered 500000 south Londoners and was published in 1856. It showed that customers of the Lambeth Water Company had a death rate in the 1854 cholera epidemic of 37 per 1000, compared with 130 per 1000 among those taking water from Southwark Water Company. The difference was that Southwark took its water close to an outflowing sewer.
• However, it wasn't until 1870 that Snow's breakthough showing cholera being a water-borne disease received universal acclaim and was accepted by the medical establishment.