These days, most people hearing the name “John Snow” will think of the character Jon Snow from HBO’s Game of Thrones, a hugely successful series based on the books by George R. R. Martin. Many of the 6 million+ viewers of this fantasy series may not know that there was another John Snow, perhaps one without the coal-black curls and swarthy good looks, but a man who changed the world of medicine and saved millions of lives. What does a fictional hero who wields a magical sword to destroy the undead atop a 700-foot wall of ice have to do with a Victorian-era physician who wielded nothing heavier than a fountain pen as he collected thousands of data points in a 1-square-mile neighborhood of London? The answer may surprise you!

In our last post, we described a pervasive disease that so affected the global population that it found its way into visual, musical, and literary works of art for centuries. What what this horrible disease? Tuberculosis.

Before we knew about germ theory and the microorganisms that caused disease, the illnesses that afflicted millions were mysteries. They acquired names that described their symptoms, their effect on behavior, or on the sheer numbers of people they killed. Without knowing anything about causes, treatment, or prevention, our ancestors feared “the wasting disease,” saw friends and relatives fall victim to “bilious fever,” and cared for loved ones stricken with “child bed fever,” “yellow jacket,” or “dysentery.”