“It was virulent beyond anything in anyone’s memory, and the most terrifying effect of this mysterious virulence was not only that it killed so many people but that it turned them against one another.”

So opens “The Black Death,” the third chapter of Otto Friedrich’s brilliant 1986 book, The End of the World: A History.

The narrative examines “the monumental, often inexplicable catastrophes that have at various times swept over humankind–moments when, for numerous people, the world did come to an end.”

Among the catastrophes vividly depicted by Friedrich:

• The Sack of Rome
• The Birth of the [Spanish] Inquisition
• The Black Death
• The Coming of [the Russian] Revolution
• The Kingdom of Auschwitz

As America comes face-to-face with the terrors of Ebola, the pages Friedrich devotes to the original plague may turn out to be as much prophecy as history.

Bubonic plague originated in Central Asia, killing 25 million people.  Upon reaching Constantinople in 1347, it spread to Naples and Venice.  Trade ships from these ports spread the plague to southern France and Italy.

It reached Paris in June, 1348, and London several months later.  By 1350, all Europe was ravaged by the plague.

Within four years it destroyed a quarter to half of the population of Europe.

The plague was caused by the bacillus Pasteurella pestis, which lives in rats and other rodents.  The fleas living in these animals transmitted the plague to people by biting them.  Within five days, the victims had died.

By the time the plague had run its course, it had killed 75 to 200 million people.

The signs of infection became unmistakable: Growths in the thighs, about the size of apples, then dark blotches and bruises on the thighs, arms and other parts of the body.

As a result of these dark blotches, the plague quickly became known as the Black Death.

“O happy posterity,” wrote the Italian poet Petrarch, “who will look upon our testimony as a fable.  Will posterity believe that there was a time when, with no deluge from heaven, no worldwide conflagration, no wars or other visible devastation…but almost the whole earth was depopulated?”

The plague destroyed not only the lives of its victims but the fragile bonds that hold society together.

“As the number of deaths increased in Messina,” wrote the Franciscan monk Michael, “many desired to confess their sins to the priests and to draw up their last will and testament.  But priests and lawyers refused to enter the houses of the deceased….

“Soon men hated each other so much that, if a son was attacked by the disease, his father would not tend him.  If, in spite of all, he dared to approach him, he was immediately infected….

“Soon the corpses were lying forsaken in the houses.  No priest, no son, no father and no relation dared to enter, but they paid hired servants with high wages to bury the dead.  Soon there was a shortage of servants and finally none at all.”

Bones of plague victims stacked by a monk at the Sedlec Ossuary.

No one knew what caused it.  Many–especially members of the Catholic clergy–believed the plague was God’s judgment on a sinful world.

Philip VI, the king of France, fearing this might be true, issued a proclamation against blasphemy. For a first offense, a blasphemer’s lip would be cut off; for a second, the other lip.  And for a third offense, the tongue.

Medical professors at the University of Paris believed that a disturbance in the skies had caused the sun to overheat the oceans near India.  As a result, the waters were giving off toxic vapors.

Guy de Chauliac, the physician to Pope Clement VI, believed that the plague had been caused by a conjunction of Saturn, Jupiter and Mars, in the sign of Aquarius.  This, he believed, had corrupted the earth’s atmosphere.

Just as no one knew what had caused the plague, no one knew how to protect oneself against it.

Among the remedies prescribed: Bleeding, purging, bathing in vinegar to purify the body and the burning of odiferous wood to purify the air.

Others trusted to faith, praying for deliverance.  Some went on pilgrimages or subjected themselves to self-flagellation to expiate their sins.  The Brotherhood of the Flagellants appeared in Dresden, Hamburg and Magdeburg, then spread throughout Europe.

For others, debauchery seemed to be the road to salvation–or at least temporary happiness while they waited for the plague to claim them.

“People behaved as if their days were numbered,” wrote Giovanni Boccaccio, “and treated their belongings and their own persons with equal abandon.  Hence most houses had become common property and any passing stranger could make himself at home.”

Yet none of the prescribed medical cures brought relief.  And no amount of religious devotion brought salvation.

As Friedrich notes: “One of the most baffling and terrifying aspects of the plague [was] its indiscriminate slaughter of the devout as well as the sinful.  If this was God’s anger, how could it be understood, much less appeased?”

The plague ravaged France, Germany, England, Spain, Norway, Poland, Hungary, Russia.  After devastating London in 1665 and Marseille in 1720, the disease mysteriously disappeared.

Some believe the common black rat was destroyed by the larger brown rat, which lived outdoors, away from people.  Others believe a milder, mutant form of the disease caused its victims to build up immunities.

No one knows for certain.