And, indeed, as he listened to the cries of joy rising from the town, Rieux remembered that such joy is always imperiled. He knew what those jubilant crowds did not know but could have learned from books: that the plague bacillus never dies or disappears for good; that it can lie dormant for years and years in furniture and linen-chests; that it bides its time in bedrooms, cellars, trunks, and bookshelves; and that perhaps the day would come when, for the bane and the enlightening of men, it would rouse up its rats again and send them forth to die in a happy city. — “The Plague,” Albert Camus

In separate research, scientists learned recently that the bubonic plague, which wrecked the lives of millions of Europeans starting in the 14th century and continuing through the 17th, indeed originated from China. The plague is said to have killed off 30 percent or more of Europe’s population at its height, and reemergences of the disease continued about every 10 years for centuries.

In the above-referenced article from The New York Times, the causal element of the plague was a bacterium known as Yersinia pestis.

According to the article:

Dr. Bramanti’s team was able to distinguish two strains of the Black Death plague bacterium, which differ both from each other and from the three principal strains in the world today. They infer that medieval Europe must have been invaded by two different sources of Yersinia pestis. One strain reached the port of Marseilles on France’s southern coast in 1347, spread rapidly across France and by 1349 had reached Hereford, a busy English market town and pilgrimage center near the Welsh border.

The strain of bacterium analyzed from the bones and teeth of a Hereford plague pit dug in 1349 is identical to that from a plague pit of 1348 in southern France, suggesting a direct route of travel. But a plague pit in the Dutch town of Bergen op Zoom has bacteria of a different strain, which the researchers infer arrived from Norway.

…

The three plague waves have now been tied together in common family tree by a team of medical geneticists led by Mark Achtman of University College Cork in Ireland. By looking at genetic variations in living strains of Yersinia pestis, Dr. Achtman’s team has reconstructed a family tree of the bacterium. By counting the number of genetic changes, which clock up at a generally steady rate, they have dated the branch points of the tree, which enables the major branches to be correlated with historical events.

In the issue of Nature Genetics published online Sunday, they conclude that all three of the great waves of plague originated from China, where the root of their tree is situated. Plague would have reached Europe across the Silk Road, they say. An epidemic of plague that reached East Africa was probably spread by the voyages of the Chinese admiral Zheng He who led a fleet of 300 ships to Africa in 1409.

“What’s exciting is that we are able to reconstruct the historical routes of bacterial disease over centuries,” Dr. Achtman said.

What’s terribly unexciting is the message pregnant in the conclusion of Camus’ “The Plague,” that the bacterium may not be done with mankind yet, and as we’ve seen through the centuries, there’s no reason to believe that it won’t rear its menacing head again at some point in the future. In isolated cases, it already has. Luckily, we live in an age of modern medicine — far alien to people in the 14 or 17th centuries — where mass outbreaks could likely be quelled.