Epidemiology 101

If I had chosen a field related to medicine and public health, it should have been epidemiology. Detecting patterns, solving mysteries, analyzing maps, tracing history: What could be more fun?

People must always have noticed some diseases spread from person to person. The word quarantine comes from Italian for forty days, the time Venice made ships from infected ports sit at anchor before anyone got off. Romeo and Juliet could have had a happy ending if no one thought a house with the plague had to be boarded up.

Collecting and mapping data has been a basic tool of epidemiology since the 1850s, when John Snow painstakingly traced a London cholera epidemic to one infected well. I highly recommend Steven Berlin Johnson’s engaging account, The Ghost Map.

With the additional tool of genetic analysis, disease detectives can compare cases of an infection to determine the route it traveled. That’s how epidemiologists discovered coronavirus came to New York primarily from Europe, not China. Clues, suspects, red herrings—these sleuths have it all.