Review of Spillover by David Quammen

During the last week of September, I found myself in Georgia looking for a good book to read. Knowing that David Quammen’s newest effort was about to be available, I walked from my hotel to a local bookseller and asked if they might have a copy.  In fact they did but it was in the back room and wasn’t supposed to be on the storeroom floor until the first of October. Fortunately, for me, they made an exception. I decided not to ask about the legality of it all and promised not to tell anybody.

Within a few chapters, I realized that this book will be a prize winning title when awards get ladled out for this season’s offerings. Quammen is a very good writer, for sure. But good writers don’t always win awards. The book, The Song of the Dodo (Quammen’s 1996 book about island biogeography) was written as well as Spillover but treats a subject that many fail to consider immediately important. My experience is that most awards are given to subjects of broader interest. 

Spillover is a book that has this broader appeal. It is about human diseases that originate in animals. Such diseases are called zoonoses. Unlike many diseases (take polio, for example) that are spread from person to person and only remain in the human population, zoonoses grow and develop in other animals and then jump hosts: on to humans. This is called spillover: when a disease agent gets to critical point in its non-human host that it makes this jump. These zoonotic diseases have great potential to spread rapidly and with devastating effect.

You are familiar with some of these zoonotic diseases: AIDS, West Nile fever, rabies, Lyme disease, some malarias, etc. If you were captivated by Richard Preston’s 1994 best-seller The Hot Zone, you will remember such maladies as Marburg virus disease and some of the hemorrhagic fevers. Quammen covers all of these and more: not as sensationally as Preston did, but with a researcher’s and a storyteller’s gift that makes this a real keeper.

Few writers put in the homework that Quammen does.  When he walks us through the complicated origins of HIV, for example, we get to meet scientists in lab coats, hidden closets in African hospitals, and animal traders that work the underground markets of Africa. Quammen also takes us to the corners of Cameroon where AIDS seems to have emerged into the modern world. Or to the jungles of Indonesia where we find malarial plasmodia living in macaques.

Quammen puts us into a different Heart of Darkness than we are used to. Conrad described an impenetrable jungle landscape that loomed mysteriously in the hinterland of civilization. Quammen lifts the canopied curtain and lets us see what dangers lie within. We find there a world of ecological disruption that disgorges the (perhaps) inevitable harvest of our previous ignorance.

These are big issues, indeed. But Spillover is also helpful in more immediate ways. The book’s discussion of Lyme disease, for example, is something that more of us should be aware of. Yes, the disease is spread by deer ticks; and yes, the forests of the Eastern US harbor the disease. But how many of us realize that deer are not the real problem?

Ticks that feed on deer will not feed on humans. The reason is fairly straight-forward: deer are the end of the tick’s life cycle. After a female tick lays eggs, the small ticks (smaller than a pin head) emerge and look for their first host which is neither a deer nor a human, but a mouse. This tiny tick will then drop off of its rodent host, develop a bit longer, and then look for another host. It is this errant arthropod that may find a human host (or perhaps it will find another mouse and feed again before it potentially finds its last host). Lyme disease is primarily a problem of forested areas that lack sufficient rodent predators. Small wooded lots can be prime examples of this. Deer are not our enemies.

Several things make zoonoses so important. Perhaps most significantly, they are very difficult (if not impossible) to eradicate.  Being able to “hide” in non-human animals, they can essentially disappear and show up at unexpected times and in unexpected places.

They are also prone to change. The very act of jumping host species creates an ecological setting for genetic change that makes many of these disease agents not only difficult to treat but likely candidates to get out of hand. Some of the most important examples that Quammen mentions are the flu viruses that are ideally constituted to this kind of change. Periodically certain forms evolve that cause us a great deal of grief.   

The punch-line of the book is when Quammen shows us a human population that looks very much like an outbreak poised on the brink of a pandemic – perhaps several pandemics. Quammen, fortunately, is not in despair – though he is clearly concerned. We have tools that other organisms experiencing an outbreak (before crashing) do not have.  We have our wits and our technology. The question remains whether or not we will decide to use them wisely.