Justinian’s Flea: Plague, Empire, and the Birth of Europe by William Rosen
My rating: 5 of 5 stars

This book was absolutely fascinating, both from a historical perspective (great depth in the background of Justinian, the empire, and the players in Justinian’s world, which is intriguing) and a scientific/epidemiological perspective.

The first half of Justinian’s Flea is the history of showing how Justinian consolidated the world’s power in Constantinople.

The second half of the book shows how a toxic bacteria – Y. pestis – that is very specific to a tiny flea that is very specific to a certain type of rat (fleas, it turns out, are incredibly picky about their hosts unless there aren’t any and then fleas go for whatever is available) decimated Justinian’s empire and ignited the formation of the Europe we see emerge in the Dark Ages.

One of the beauties of Rosen’s writing is his attention to detail. As he explained, at the minute level and in graphic detail, how Y. pestis is composed and keeps itself alive, I marveled that the human race is even alive considering that while there are good bacteria, the really bad ones – and Y. pestis is responsible for bubonic plague pandemics – outnumber us by the billions.

Everything in the environment – climate (the Y. pestis rat, which is a grain rat, needs colder and wetter-than-normal weather to reproduce by leaps and bounds and create the huge numbers of infected rats that can create a pandemic), trade (rats, which I didn’t know, are large sedentary, traveling on their own a little over two times the length of an American football field in their normal 2-year life span; however, the rat that carries the flea infected with Y. pestis travels all over the world in the grain shipments it is a part of), and a bunch of people crowded densely into a relatively-small amount of space) – must come together to create a bubonic plague pandemic.

In 542, this coalition happened. Historical and scientific records show a cooler and wetter year than was normal (although the exact cause is not known, the most likely culprits were a meteor event or a volcanic eruption – the fragments from the meteor or the ash from the volcano would have disrupted the weather for a significant amount of time).

Alexandria, Egypt is the indisputable source of the rats because they were the world’s grain producers and traders at the time.

As their grain ships set out for the large port cities at the time – with Constantinople being one – history was about ready to plunge from what is now known as the Classical Age into what we know as the Dark Ages.

All because of a single bacteria, a specific type of flea, and a specific type of rat that was incredibly fond of grain.

It’s kind of incredible to think about. But it’s not a past event. One of these could happen again at any time. And that’s the sobering part of this book.

If you like history and you like science and you want to see an absolutely fascinating, albeit devastating, intersection of the two, I highly recommend this book.

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