Visualizing Disease Outbreaks: A Question of Scale?

Vaccinations are a hot-button issue right now as measles outbreaks crop up throughout the United States. Measles, mumps, rubella, whooping cough, and polio are all deadly diseases that can be easily prevented with vaccines. Outbreaks of these diseases have been occurring worldwide for a long time, but outbreaks have been increasing in the U.S. while going down in other countries, according to the video below:

The video is kind of terrifying—more and more colored dots representing these diseases get added each year, and suddenly the whole world is suffering from these horrible outbreaks. But is that an accurate portrayal of the data?

The map in this video is based on a map (below) created by the Council on Foreign Relations, showing similar circles representing the size of outbreaks. The smaller the circle, the smaller the outbreak. Makes sense, right?

The scale that these circle sizes are based upon may be misrepresenting the data. The circles don’t increase in size at the same rate that the number of patients affected by outbreaks increase. One patient per outbreak is the absolute lowest number, but the maximum number of patients in an outbreak represented on this map is 134,042. This scale makes a single-patient “outbreak” look more dramatic than it is—and makes the 134,000-patient outbreak look smaller.

Furthermore, what would happen if you took the number of cases of each disease and divided it by the total population to get a percentage? The high number of outbreaks in Asia would likely look more tame compared to the rest of the world—the sheer fact of population can skew the representation of these data.

This does not mean that the threat of measles and these other diseases is trivial. In fact, there is a better visualization of the current measles outbreak in the United States by The New York Times. Examine their scaling on measles outbreaks over time and compare with the scaling of the Council on Foreign Relations map above.

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