Bangwoori
This is Broad Street in Soho in the center of London, right? By the way, are you the person who traces the cause of a disease?
John Snow
Yes, I am. I am John Snow, a doctor. I am currently searching for the cause of cholera, the epidemic spreading throughout London.
Bangwoori
So, instead of treating patients as a doctor, you are walking around the streets investigating something?
John Snow
In the first week of the outbreak, 93 people were rushed to the hospitals, and the number of patients increased rapidly the following week. So, I am marking on a map where the patients lived, one by one. The black markers you see here are where cases of the disease occurred.
Bangwoori
There are really a lot of patients! But can you identify the cause of the disease only by looking at the map?
John Snow
A lot of doctors still believe that the cause of cholera is poisonous, foul-smelling air. But I think there is another cause. I was born in York, and I have seen wastewater flowing from coal yards, markets, and cemeteries polluting the rivers and causing diseases.
Bangwoori
So, that’s why you are investigating the cause of this terrible disease by looking at a map to see where the patients got their water from?
John Snow
You are right. It seems this public pump could be a vital clue. I found that most of the cholera patients living in this area drank water from this pump, while even patients located quite a distance away also drank from it. However, residents living nearby but drinking water from different sources did not get sick. I think the cause of the disease is contaminated water flowing into this pump, so I have to stop the pump from being used.
Bangwoori
Wow! You, doctor, have just removed the pump handle. So now you can prevent people from drinking contaminated water.
John Snow
But this pump isn’t the only problem. The real cause lies in that massive River Thames. As people flock to London in the wake of the Industrial Revolution, wastewater and sewage are flowing into the river without being properly treated. In fact, there were far more cholera cases in the areas supplied with contaminated water compared to the upstream regions where this sewage did not flow in.
Bangwoori
So, finally, all the clues you were looking for on the map lead to ‘water’ as the cause of this cholera epidemic!
John Snow
That’s right. Water is indispensable to humans, but contaminated water can threaten human health. That is why, especially in cities where many people live close together, it is very important to safely supply clean water.
Bangwoori
Now I understand fully! You have marked the traces left by the patients on a map and followed the clues one by one to uncover the link between cholera and water. You really deserve to be called ‘The Detective tracing Cholera’!
John Snow
Ha!ha! Detective — that’s an interesting nickname! I just want people to be able to drink clean water with peace of mind about its effect on their health.
Bangwoori
When I get back home, I will also think again about how the clean water we are fortunate to drink every day comes to us.
where we meet and talk with historical figures
related to water.
John Snow(1813-1858)
A British physician and pioneer of epidemiology. When a cholera epidemic broke out in London in 1854, he traced the locations of infected patients and the routes of drinking water use, revealing that contaminated water was linked to the cholera epidemic. By identifying the causes of diseases through scientific investigation and collection of data, he laid an important foundation for the development of modern epidemiology and public health.