Death by Microbe

Every one of these six pieces starts the same way: something too small to see, and an empire that didn’t see it coming. Malaria wearing down the ancient Mediterranean for centuries. A plague arriving in Athens by ship in 430 BCE, three years into a war Pericles thought he had a plan for. Bubonic plague reaching Constantinople in 542, while Justinian was still finishing the job of reuniting Rome. The same bacterium returning to Europe in 1347, killing a third of the continent and handing the survivors the leverage to end feudalism. Smallpox travelling with the Spanish into a Aztec capital its own soldiers couldn’t have taken alone. Typhus, not the Russian winter, breaking Napoleon’s army before it ever reached Moscow.

None of these are stories about germs, exactly. They’re stories about what a civilisation looks like at the exact moment it turns out to have a body — walls that keep people in as easily as they keep enemies out, ports that move grain and also fleas, an army that is really just several hundred thousand people standing very close together. The empires in this issue didn’t fall to better armies. They fell to arithmetic: a pathogen doesn’t care how many battles you’ve won.

What ties history to biochemistry here is the same thing every time: the mechanism is small and the consequence is enormous. A bacterium that disables a single class of immune cell ends up deciding which language is spoken in the eastern Mediterranean for the next thousand years. A louse that can’t survive a wash ends up deciding who rules Europe in 1813. That gap — between the size of the cause and the size of the effect — is why this issue exists.

Co-editors — Naasha Mahadevia and Rhea Hiremath