Dr. John Snow-  The father of modern epidemiology

John Snow memorial and public house on Broadwick Street, Soho Photo Credit- CC BY-SA 2.0

John Snow memorial and public house on Broadwick Street, Soho Photo Credit- CC BY-SA 2.0

Clean water is essential for life.  Without it, we die quickly of horrible diseases.  As modern life progressed, our cities got dirtier and dirtier.  Cities realized quickly they needed to do something to get the streets cleaner.  In 1858, the city of Chicago even had all of its buildings lifted four feet to make room for a sewer.  Other cities followed suit, which was good.  One problem.  Most of the sewers emptied into water sources.  The water in Chicago, for example, was so bad that dead fish would show up in bath water.  Residents nicknamed their water “chowder”.  The introduction of the flush toilet made the water supply worse.  It could be called a catastrophic success, as the rapid adoption overloaded the sewer system with waste.

Things were not much better across the Atlantic in England.  Cholera was running rampant.  No one knew where the disease came from.  In fact, most people thought it came from bad air.  Into this epidemic, enter John Snow.  Not the guy from Game of Thrones, but Dr. John Snow of York, England.  Growing up in a poor neighborhood in York, at 14 he became apprenticed to a surgeon in Newcastle on Tyne.  A cholera outbreak swept into Newcastle from Sunderland, and Snow worked with the miners as they fell sick.  Despite being in the same fetid environment, Snow did not get sick.  This planted an idea in his mind, but it did not take root until later.

Snow moved onto work at Westminster hospital in London in 1837, and completed his studies at the University of London in 1844.  In 1854, an outbreak of cholera in Soho.  Most people ran in terror, but Dr. Snow risked his life to try and understand the cause of the disease.  He theorized that the cause of cholera must be not from air, but from water.  Clean water was a premium in London as most water was pumped from shallow wells and carried into individual homes.  There were water lines for upper class houses that brought water directly from the Thames.  However, cross contamination from the hodge podge of sewers was easy and happened often.  Snow set out to get the data to prove his theory.

During the outbreak, Snow stayed in the neighborhood and mapped the data.  He created a map of the thirteen public pumps in the neighborhood and then recorded the cases of cholera house by house.  A pattern of deaths emerged around one pump at the corner of Broad and Cambridge Streets.  He recorded, “In some of the instances, where the deaths are scattered a little further from the rest on the map, the malady was probably contracted at a nearer point to the pump.”   He found that one lady traveled several blocks because she liked the taste of the water of that particular pump.  She was dead in two days.  Another pattern he noticed was there were no deaths among the workers at the brewery located one block from the Broad Street pump.  The process of making beer includes boiling water and fermentation, which kills bacteria.  The brewery workers were allowed to drink all the beer they wanted, and therefore missed being infected.  And who said beer wasn’t good for you?

Snow's map of the Broad Street outbreak Photo Credit- https://www.udel.edu/johnmack/frec682/cholera/

Snow’s map of the Broad Street outbreak Photo Credit- https://www.udel.edu/johnmack/frec682/cholera/

Snow drew water from the suspicious pump and examined it under a microscope.  There was some bacteria in that water that was not in the water samples from other pumps.  Snow had all the evidence he needed.  Despite skepticism from neighborhood authorities, Snow removed the handle from the Broad Street pump.  The outbreaks drew to a close.  Snow observed, “There is no doubt that the mortality was much diminished, as I said before, by the flight of the population, which commenced soon after the outbreak; but the attacks had so far diminished before the use of the water was stopped, that it is impossible to decide whether the well still contained the cholera poison in an active state, or whether, from some cause, the water had become free from it.”  Further analysis found that the well at the Broad Street pump had been contaminated from a diaper from a sick baby that was thrown into a nearby cesspit.

Snow published his map, which was more than just a map but was a detailed statistical analysis.  There were still naysayers to the water born disease theory and the pump handle of the well was soon replaced.  To symbolize this, members of the John Snow Society now remove and replace a pump handle to symbolize the continuing challenges for advances in public health at the Annual Pumphandle Lecture in England.

ER

Sources available on request