John Snow was a physician who was working in London during the cholera outbreak in 1854. He did not believe miasma theory was responsible for the outbreak of cholera in 1854. Therefore, he carried out an investigation to try to establish the cause of the outbreak.

John Snow’s investigation

• Focussed on cholera cases in Soho, London.
• Snow plotted all the places where people had died from cholera.
• From the map, he was able to work out that they had all drunk water from the same pump on Broad Street.
• It is believed that the drinking water was contaminated by sewage leaking into the water supply from a nearby cesspit.
• Snow knew that none of the workers at a local brewery had been taken ill with cholera.
• The people who worked at the brewery had been drinking beer, rather than water from the pump.
• Snow persuaded the local council to remove the handle from the pump so it could not be used.
• Cases of cholera in the area stopped as people were forced to go to other pumps for their water.

What was the significance of Snow’s work?

Snow’s investigation proved that cholera was a waterborne disease. This was an important step forward in disproving the miasma theory. However, Snow could not explain that there were germs in the water that were causing the illness. Therefore, many people continued to believe that cholera was caused by miasma. It was not until Louis Pasteur’s germ theory that there was evidence to further support Snow’s work.

This then led to further public health reforms. Action was taken to provide people across the country with a clean water supply.