Exploration, Integration: A Review of An Unnatural History of Emerging Infections

One of the best aspects of infectious disease is the grand scope which they encompass. It can be very hard to tell the story of just one infectious disease let alone the entire field. A 2013 book which I just finished attempts to do that and, in my view, is highly successful. Emory University professors Ron Barrett and George Armelagos's An Unnatural History of Emerging Infections is a must read for anyone interested in the field of emerging infectious disease. 

The book is written from a philosophical viewpoint that seeks to integrate the microbiological world with the human world. The human world, characterized by a litany of changing conditions, is shown to be very explanatory when it comes to the infections we contract. A key theme of the book is understanding human epidemiological transitions of which there have been three: from  a nomadic lifestyle to a sedentary one 10,000 years ago; the Industrial Revolution; and the modern era of urbanization/globalization coupled to population aging. Through these epidemiologic transitions disease patterns change from an age of pestilence to a period of receding epidemics to an era of manmade/degenerative diseases. It is important to realize that a nomadic lifestyle is not one in which large infectious disease outbreaks can flourish given the low population density and the constant movement. "Heirloom" infections (those that infected hominid species pre-humans) and "souvenir" infections (acquired in activities of daily living) were likely the majority of infections during these times.

From this lifestyle humans increasingly moved to agricultural societies which provided many advantages over the prior lifestyle -- principally in the ability to store calories via agriculture. On balance, this was the right choice for our ancestors but it did create kindling for infectious disease outbreaks as population density increased, contact with animals became more frequent, and food sources changed. This new set of conditions was conducive to zoonotic spread of infections as well as the persistence of endemic infections. Only with the advent of sanitary and, later, medical innovations characterized by the Industrial Revolution would these pestilences be tamed. 

There are countless additional pearls in this book that include a discussion of the competing Attenuation and Virulence Hypotheses and the role of non-human primates in human diseases. 

To me, this book is a valuable resource that I thoroughly enjoyed reading. It greatly deepened my understanding of the field reinforcing my knowledge and helping me make wider integrations with history and anthropology. I highly recommend it.