John Snow (15 March 1813 – 16 June 1858) was a British physician and a leader in the adoption of anaesthesia and medical hygiene. He is considered to be one of the fathers of epidemiology, because of his work in tracing the source of a cholera outbreak in Soho, England, in 1854 using spatial analysis.
John Snow was born into a labourer's family on 15 March 1813 in York and at 14 was apprenticed to a surgeon living in Newcastle-on-Tyne. In 1836, he moved to London to start his formal medical education. He became a member of the Royal College of Surgeons in 1838, graduated from the University of London in 1844 and was admitted to the Royal College of Physicians in 1850.
In 1849 Snow published a small pamphlet "On the Mode of Communication of Cholera" where he proposed that the "Cholera Poison" was spread through the contamination of food or water. This theory was opposed to the more commonly accepted idea that Cholera, like all diseases, was transmitted through inhalation of contaminated vapours.
In August 1854, a cholera outbreak occurred in Soho, London. After careful investigation by Snow, including plotting distribution of deaths on a map, he determined that an unusually high number of deaths were taking place near a water pump on Broad Street. Snow's findings led him to petition the local authorities to remove the pump's handle. This was done and the number of cholera deaths was dramatically reduced.
Snow's classic study offers one of the most convincing arguments of the value of understanding and resolving a social problem through the use of spatial analysis.
The image on the right shows a section of the original map by Dr. John Snow showing the clusters of cholera cases in the London epidemic of 1854.
Using Map Intelligence
London's Soho in 1854 was a dirty, grimy place with cow sheds, grease-boiling dens, slaughter houses and overcrowded housing under which numerous cess pits festered. Drinking water was provided by the way of street water pumps.
In the 1854 London Cholera epidemic the worst-hit areas at first were Southwark and Lambeth. Soho suffered only a few, seemingly isolated, cases in late August. Then, on the night of the 31st, what Dr Snow later called "the most terrible outbreak of cholera which ever occurred in the kingdom" broke out. During the next three days, 127 people living in or around Broad Street died. By 10 September, the number of fatal attacks had reached 500 and the death rate of the St Anne's, Berwick Street and Golden Square subdivisions of the parish had risen to 12.8 per cent -- more than double that for the rest of London. That it did not rise even higher was thanks only to Dr John Snow.
John Snow is viewed by many as a pioneer in disease mapping. He used bars on a map to represent deaths that occurred at the specified households. His interviews and investigations led to the removal of the handle on the Broad Street pump.
Today, John Snow would have probably kept his data in an Excel Spreadsheet and used Map Intelligence to quickly create a mapping application that could analyze his interview data.
The Map Intellgence "1854 Broad Street Cholera Outbreak" Application
JOHN SNOW Greenwoods 1827 map of London Using the MI Density Surface tool we can show where there are concentrations of deaths. We can see the outbreaks in Southwark and Lambeth to the south of the Thames. The dark blue area to the north west of the Thames, indicates that this particular area has an extremely high number of deaths. https://www.integeo.com/images/2016/dj-image-slideshows/john-snow/16042010_Broadstreet_02_large.gif Zoom to Marquee Using the Zoom to Marquee navigation tool, we can draw a rectangle around this high density hotspot, this allows us to zoom into the selected area to take a closer look. https://www.integeo.com/images/2016/dj-image-slideshows/john-snow/16042010_Broadstreet_03_large.gif Pump Points On Zooming in, the map view changes to a street level view of the Soho area of London. The individual pump points can be seen represented by the blue circle icon and a label gives the name of the pump. A Map Intelligence radius relationship layer has been used to show a 1 km circle around each pump. The circles are color-coded according to the number of deaths around each pump. Yellow circles indicate the number of deaths were less than 30, orange circles less than 50, etc. https://www.integeo.com/images/2016/dj-image-slideshows/john-snow/16042010_Broadstreet_04_large.gif Radius Relationships around pumps The red circle indicates that there were over 200 deaths around the pump in Broad Street. Using the Zoom to Marquee navigation tool we will investigate this area further. https://www.integeo.com/images/2016/dj-image-slideshows/john-snow/16042010_Broadstreet_05_large.gif Viewing Death points On zooming in we see the Broad Street area of Soho and the Broad Street pump . John Snow used horizontal black lines to represent a death, in the MI application these points are represented by a red circle icon. We can see the high concentration of deaths in the area around the pump and in Broad Street itself. An Information pop-up box display details about the individual who died. In this image we see the details of Frances Lewis, who at the age of 5 months, was the first to die in the outbreak. https://www.integeo.com/images/2016/dj-image-slideshows/john-snow/16042010_Broadstreet_07_large.gif Information Popups: Active Links When selecting an Information Popup active link, the Death Certificate of the individual is launched. In this example the Death Certificate of Frances Lewis can be seen. The date of her death was 2nd September 1854, she was the daughter of Thomas Lewis, a local Police Constable. https://www.integeo.com/images/2016/dj-image-slideshows/john-snow/16042010_Broadstreet_08_large.gif
Slideshow: Click image to view a larger version.
