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The Black Death and Justinian’s Plague: History’s Worst Pestilences

Khalid Elhassan January 8, 2025 13 min

Plague - Illustration from the medieval Liber Chronicarum 1, depicting skeletons rising for the dance of death — Illustration from the medieval Liber Chronicarum 1, depicting skeletons rising for the dance of death. Live Science

7. The Black Death and Weather Cycles

Plague - An oriental rat flea, plague's primary vector, engorged with blood — An oriental rat flea, plague’s primary vector, engorged with blood. Wikimedia

Bad weather kills off the usual rodents – which don’t live amongst humans – that host the fleas that host Yersinia pestis. The fleas then flee to rodents like rats that do live among humans. A Black Death outbreak starts. Even as they kill humans, the infected fleas also wipe out their rat hosts, and thus extinguish the plague. Ten or fifteen years later, bad weather would again decimate the usual rodents that typically host the infected fleas. Once again, the fleas flee to rats, whose populations by then have recovered. The rats reintroduce the plague-infected fleas to humans, and another Black Death outbreak occurs, that lasts until the rats die off.

Written by

Khalid Elhassan

A lifelong history buff, I developed a particular passion for WW2 history as a child, when I spent hours listening to my grandfather, enraptured, as he recounted his wartime experiences in the British East African Campaign and with the British 8th Army in North Africa.

I graduated with a history BA from George Mason University, then went on to get a JD from the University of Virginia School of Law. After lawyering for a decade, I moved to sunny Rio de Janeiro and a less demanding career, opening a tourism agency in Copacabana.

A big chunk of my free time is spent blogging (you can follow me on Quora https://www.quora.com/profile/Khalid-Elhassan ) or freelance writing, mostly about my favorite subject, history.