A permutation of the bubonic plague, which back in 541C.E.

Demolished the Byzantine Empire, killing an estimated 30 to 50 million

people, which at the time was a significant portion of the total population of the planet,

resurfaced in Europe in 1347, gaining new monikers, the black death and the great mortality among them, and killed another

75 to 200 million people, mostly in Eurasia and North Africa, over the course of just a handful

of years, though it continued to recur in these regions for the next several centuries.

The city of London was hit especially hard by these recurrences,

experiencing new outbreaks every 10 years or so, between 1348 and 1665, with 40 serious

outbreaks and a lot of smaller ones recorded during that period. And though the people living

during this time didn't have germ theory or even a real

concrete sense of why this kept happening, why people kept dying in horrible ways on such a regular

basis, they did, mostly through trial and error, figure out that proximity was part of the equation,

and thus came up with early versions of quarantine and social distancing.

Folks who were coming in from other regions were kept on their ships at port for periods of time,

to allow any diseases present in the people manning those ships to run their course before they were allowed ashore.

And people who came down with the tell-tale swollen lymph nodes, or

bubos, of the bubonic plague, were isolated in their homes. A bale of hay strung up outside

to indicate the person living there was sick with this affliction, and if you were infected

and moving about in public, you had to carry a white pole so that other people would know and

would be able to keep their distance from you. The degree to which this recurring plague was

destabilizing, though, even with the slow introduction of these helpful policies, cannot be overstated.

Every 10 years or so, when a new pandemic wave occurred, about 20% of the population was killed.

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