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Data Visualization and Cholera: An Unexpected Connection

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Radial chart london cholera

Data Visualization and Cholera: An Unexpected Connection

Necessity is the mother of invention, and in the mid-1800s, understanding the spread of cholera was a matter of life and death.

Ruthless Efficiency

Cholera was a ruthlessly efficient killer, with both rapid onset and severe symptoms. By the time the disease made its way to London and New York in the early 1830s, hundreds of thousands of people had died across Europe, Africa, and Asia.

Not only our personal and national interests, […] it may be said without exaggeration, [that cholera] concerns the whole human race.

– Thomas Whiteside Hime

Needless to say, the human race was concerned. Thanks to high-speed printing press technology, daily newspaper circulations were rising dramatically, and this allowed journalists to experiment with new reporting techniques, including charting data.

cholera line chart

At the time, the chart above was such a novel approach that it required four paragraphs to explain how to read it. People of that era were simply not used to seeing data in a visual form. At a glance though, the chart is extremely effective at communicating a grim message: cholera had ravaged New York City over the summer of 1849.

Despite the concerted push to eradicate the disease, the medical community was still largely in the dark about how to prevent future outbreaks. Because doctors could treat numerous patients without falling ill, it was assumed that a miasmic environment (i.e. slums, densely-packed housing) was causing the spread.

Data Viz in the Time of Cholera

Today, we have tools that allow us to map just about anything, but in the mid-1800s, mapping data was still an innovative concept.

As early as the 1830s, geographers began using spatial analysis to study cholera epidemiology. The heat map below shows which sections of Paris were hardest hit by a recent outbreak of cholera.

1832 cholera map paris

In 1854, Dr. John Snow was convinced that cholera was spreading via tainted water and decided to display neighborhood mortality data directly on a map. This method clearly revealed a cluster of cases around a specific pump.

john snow cholera map
View the full version of the map here

The result is one of the most influential maps in modern history.

In addition to the real-world utility the map provided in helping physicians understand how cholera was spreading, it also exemplified a seismic shift in thinking that opened up new avenues for data to be analyzed and displayed.

Despite the tragic circumstances of the time period, we can be thankful that the urgency of the situation allowed the world’s pioneering researchers, journalists, and physicians to experiment with new data visualization techniques to better understand the world.

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Maps

Mapped: The World’s Wettest and Driest Countries

From tropical rainforests to the sandy deserts of North Africa, the world’s wettest and driest countries are a study in contrasts.

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A cropped map of the wettest and driest countries in the world along with their average annual precipitation in millimeters.

Where are the World’s Wettest and Driest Countries?

This was originally posted on our Voronoi app. Download the app for free on iOS or Android and discover incredible data-driven charts from a variety of trusted sources.

From tropical rainforest nations to the sandy deserts of North Africa and the Middle East, the world’s wettest and driest countries are a study in contrasts.

We map and rank the countries that receive the highest and lowest average annual precipitation in millimeters, per latest data from the World Bank.

Ranked: Top 10 Wettest Countries

Colombia tops the list of nations with the highest average precipitation at 3,240 millimeters (128 inches) in a year.

Its Tutunendo district is the one of the world’s wettest places, averaging nearly 12,000 mm (463 inches) of rain annually.

RankCountryAverage Annual
Precipitation (mm)
1Colombia3,240
2Sao Tome & Principe3,200
3Papua New Guinea3,142
4Solomon Islands3,028
5Panama2,928
6Costa Rica2,926
7Samoa2,880
8Malaysia2,875
9Brunei2,722
10Indonesia2,702

Note: Figures are rounded.

Off the coast of Africa however, Sao Tome & Principe is not far behind Colombia, receiving about 3,200 mm of rain in 2020.

Papua New Guinea and the Solomon Islands also average more than 3,000 mm of rain in a year, and Panama (2,928 mm) rounds out the top five.

Noticeably, all 10 countries lie in close proximity to the equator, and near oceans, where rising hot and humid air leads to abundant rainfall.

Ranked: Top 10 Driest Countries

On the other end of the scale, Egypt records the lowest average annual rainfall across all countries, at 18 mm (0.7 inches). For comparison, Colombia receives nearly 180x the amount of rain Egypt does.

RankCountryAverage Annual
Precipitation (mm)
1Egypt18
2Libya56
3Saudi Arabia59
4Qatar74
5UAE78
6Bahrain83
7Algeria89
8Mauritania92
9Jordan111
10Kuwait121

Note: Figures are rounded.

In fact, countries from North Africa and the Middle East make up the entirety of this list of the driest countries in the world.

Learn More About Rainfall From Visual Capitalist

If you enjoyed this post, be sure to check out Mapping the Unequal Distribution of Global Precipitation which divides the world into two halves: one that receives more than global average of rain (or snow), and one that receives less.

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Voronoi, the app by Visual Capitalist. Where data tells the story. Download on App Store or Google Play

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