CGU4U/4C
Unit 1: Geographic Skills
Stopping the Spread of Disease: Cholera Outbreak London 1854
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Background:
Cholera has been a scourge of the human race for thousands of years. Its victims die from massive dehydration. Outbreaks of it in England in 1831 and
1848 caused large numbers of deaths; the 1831 outbreak killed some 50,000. There was no effective treatment for cholera; the fact that disease could be
caused by bacteria was not known. Louis Pasteur's discovery that specific diseases are caused by specific bacteria was in the future (1865). The means
of transmission of cholera had not been proven, but "everybody knew" that it spread through "miasmas," or clouds of toxic gases that supposedly came
from such source as sewers, dumps, open graves, cesspools and any other putrid sites.
Cholera had been at a low level in Soho in late summer of 1854. That all changed on the night of August 31 and
September 1st, when 56 new cases of cholera were reported. As of September 2nd, the total reached 315 cases with 197 deaths
already. The outbreak hit hard and fast. It would ultimately kill over 600 people in Soho. Determined to get to the root of what
caused the outbreak Dr. John Snow decided to employ his knowledge of medicine and an unlikely tool Geography …… rather
Spatial Analysis.
CGU4U/4C
Unit 1: Geographic Skills
Review Of Geographic Skills Needed to Solve the Mystery:
1. UTM grid systems: Eastings (left-right vertical lines) Northings (north-south horizontal lines)
How to read: 2 digit Eastings first, 2 digit Northings second Ex.
a)What is located in grid 2861? ________________________
2655?_____________________________
Any small object or one located part way between grid lines include an extra value for Eastings and Northings to create a 6 digit code. Depending on
how far across a grid square you are (close =1 halfway= 5 far way =9) that extra digit is subject to change.
b) What is located at 245572? ______________________
2. Spatial Data: On the map you will notice that there are black bars locate along the side of each street. These represent locations where Dr. Snow
recorded a cholera case or death. He used a graph to display this information because it was far more organized than points that would have made
the map tougher to interpret. The way you REPRESENT DATA in a geographic study is extremely important!
c) Which 4-digit coordinate had the highest number of cholera cases/deaths? ________________________
d) What can be said about the grid squares surrounding this pocket of increased cases? __________________________________________________
* colour code this general area as the “hotspot” of the cholera outbreak
e) What happens to Cholera cases as you get further away from this location?
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This has brought us to the first 2 concepts of Geographic Thinking:
1. Spatial Significance: The importance of a particular location and the unique features of that location
The spatial significance of the Dr. Snow’s map
is:_____________________________________________________________________________________
2.Patterns and Trends: the ability to recognize repeating, similar or opposing characteristics in a particular setting over space and time.
The patterns & trends of Dr. Snows map are:
________________________________________________________________________________________
f) What do you think Dr. Snow concluded about this hotspot of cholera cases? How was it spatially significant?
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3. Temporal Data:
Throughout his scientific research and spatial data analysis, Dr. Snow discovered:
 Cholera WAS NOT likely transmitted through the air via miasmas.
 Cholera WAS likely transmitted through something eaten or drunk.
 The ferocious diarrhea that characterized cholera was likely a factor in the spread.
 Contaminated water supplies likely produced outbreaks.
 Cholera was likely due to some parasite or other tiny germ.
Upon further research he tried to correlate environmental conditions before, during and after the outbreak to see if there was an explanation
Two conditions he studied were Rainfall and Temperature
Temperature
Rainfall
Rainfall
mm
Temp
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C
Date
Date
4. Identifying Relationships:
Analyze the DATES on the above graph and compare to the date when the cholera epidemic erupted. (see background info for exact dates ) What
were the environmental conditions like just before or during the explosion of cholera cases?
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CGU4U/4C
Unit 1: Geographic Skills
This has brought us to the 3rd concept of Geographic Thinking:
3. Interrelationships: The connections between the physical and human aspects of the environment
Discuss the interrelationships between temperature, rainfall and the prevalence of cholera cases:
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NOW YOU ARE ON YOUR OWN: You have the same amount of information that Dr. Snow had when he found
the cause of the cholera outbreak.
How will you solve it?
1. Analyze the map and its specific features (roads, buildings other). Is there anything else of spatial significance?
2. Are there any more patterns, or interrelationships you have yet to find between cholera cases and features you see on
the map? LOOK for them! (refer to list of discoveries on previous page)
3. Are there any characteristics of how cholera spread that can be explained by the map?
4. Come up with a hypothesis that explains the occurrence (what caused it) and resulting spatial distribution (geography) of
cholera cases.
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CGU4U/4C
Unit 1: Geographic Skills
The Answer:
He studied environmental conditions that could contribute to the spread of the
disease.
Warm temperature promoted bacterial growth!
High levels of precipitation led to an influx of surface runoff into wells. This runoff
contained fecal matter and thus contaminated the drinking water!
Dr. Snow recognized the spatial significance of the outbreak by isolating the
hotspot of cholera cases. He found a “focus area” for his study.
People gathered drinking water from 1 of 9 pumps in the area (usually the closest
one to their home.
Higher amounts of people living on Broad Street became ill focusing him in on
the Broad Street Pump.
As an act of vandalism he tested his hypothesis by breaking the handle off the
pump so it could not be used.
This stopped the outbreak and cholera deaths dropped to 0 within a week
meaning that his hypothesis was proven true.
But….. more questions:
1. Why did some people in farther neighbourhoods still get sick?
2. A local prison had zero cases of cholera. Why?
3. A restaurant near the pump had dozens of patrons fall ill or die?
4. None of the workers in a brewery nearby got sick?