How can a flea change a government? It’s possible if the flea is Xenopsylla cheopis (X. cheopis, for short), otherwise known as the Oriental rat flea, which lives on rats and drinks their blood. In the five years beginning in 1347, one-third of the European population -- estimates range from 20 to 70 million people -- were infected by X. cheopis, which carries Yersinia pestis, the bacillus of the black plague. These people all died of the disease.

Where Did It Come From?

At the time, no one knew what brought this disease. Miasmic air? A punishment from God? Two centuries later, the name "Black Death" was coined for the plague (black in the sense of something evil), but in the 14th century people just called it the “Great Mortality,” or, more colloquially, the “Big Death.” It hit just as Europe was emerging from the Dark Ages. Populations were growing and urban centers were becoming densely populated.

Better Wages

The arrival of the plague (both the bubonic and a virulent pneumonic form of the disease that killed in less than two days) had a number of effects on the way European countries were governed, some of them surprisingly salutary. It hastened the end of the feudal system, mainly because you can’t have a feudal system if there are almost no serfs left to work your land. Aristocratic landowners were forced to give peasants a tax break, provide communities with charters, and even pay a wage to keep people working their lands. This shortage of labor persisted even 20 years later, because of the number of children who had died, and continued higher wages contributed to the eventual rise of the middle class.

A Shortage Of Politicians

The plague came along during the Hundred Years' War between England and France, both of whose governments were staggering under the expense of maintaining the lengthy conflict. Revenues from taxation, the chief source of funding the war, came almost to a standstill, particularly in France. Another unexpected result of the number of deaths was that there was a shortage of politicians. In England, the number required for a quorum in the City Council was halved by decree, just to keep the government going. And there was so much property left ownerless after all the plague deaths, the government had to appoint special judges and commissions to decide the cases of survivors fighting over it.

Pogroms

The plague also led to the scapegoating of Jews, who may have been less hard hit because they already lived in communities separated from the mainstream, and because kosher practices led to better hygiene. Right after the black plague hit, the Holy Roman emperor gave municipalities the right to expel Jews, which led to severe pogroms, particularly in Germany.