At least 25 million people were killed in the empire.

It was recorded in 540 in the Nile delta, and because this was the grain source for Constantinople, the germs in the fleas on the rats in the ships soon were causing a plague within the city. Rosen explains how the bacterium was a relatively harmless type, perhaps causing a mild flu, but then it harnessed the flea as a means of transportation, and while evolving to turn off the defenses of the flea, it became deadly to humans. For all his accomplishments, Justinian could not overcome the devastation caused by the rat, the flea, and the bacterium _Yersinia pseudotuberculosis_. Justinian was shrewd in his choice of advisors, and never chose better than his chief general Belisarius, who conquered Vandals in Africa and Ostrogoths in Italy, as well as a late glory in defending Constantinople against the Huns. He had a considerable ego, revealed in his own writings, and little respect for his predecessors or especially for anyone whom he considered an enemy of the church. He stuck around Constantinople to work, and had little interest in visiting his military conquests. He did not pay much attention to his appearance, and he tended to asceticism. Justinian was a hard worker, productive to the point of robbing himself of sleep. He was born in a Balkan hill town in 482 CE, but an uncle, a general in the imperial guard, adopted him, took him to Constantinople, and got him an education. The backbone of the book is a biography of the Emperor Justinian himself. Not every hobbyist could make his obsession interesting, but Rosen's book swarms with so many facts that it is always surprising and never dull. It is crammed with religious, military, and political history, along with large doses of epidemiology and bacteriology (to help explain how bubonic plague works) as well as an addendum of entomology (to help explain the equally history-making silkworm). This is his first book as author, and it shows all the enthusiasm of a hobbyist eager to let others know just how interesting is the subject of his particular fascination. William Rosen has publishing credentials, but they are in the business of publishing, where he has been a senior executive.

It is not written by an academic with long publishing credentials behind him.

_Justinian's Flea: Plague, Empire, and the Birth of Europe_ (Viking) is a strange book in many ways. If you are like me, the history of the sixth century Mediterranean, especially Constantinople, is one vague gray area, but it doesn't have to stay that way. And changes fifteen hundred years ago, among ancient societies that are irretrievably lost except to scholars, created contingencies that have made our world what it is, with no way possible to conceive all the 'what ifs' that have thereby fallen out to give our current political, religious, and social situation.

Justinian's Flea by William Rosen