Tuesday, May 21, 2013

Book review: Spillover by David Quammen -

This is the best book I have read in a long time. It is like a mystery thriller played out in various exotic locations around the world, that simultaneously, gives the reader intriguing and accurate knowledge about various exotic but dangerous pathogens that have the potential to forever change life as we know it. In other words, if you would put the Selfish Gene by Richard Dawkins, a travel diary book by Bill Bryson, and an Agatha Christie thriller in the mixer, you would get something like this. It just doesn't get better than this!

David Quammen’s writing is accessible and throughout the book I was amazed by his ability to explaining difficult scientific concepts in a way that makes the reader understand... even crave science. Though I have read many scholarly articles, no single text I can recall have given me  such a deep understanding and appreciation for a scientific subject. I have always been fascinated by bacteria and viruses, however this book multiplied my fascination and my appreciation for the scientists that study viruses and other pathogens in humans as well as in other species.
This book is about spillovers (surprise!). A spillover is when a virus or a bacteria which normally live in one species transfer to a different species. Normally this transition spells the end for the pathogen because they evolved to live in their host species and not in the new species, but sometimes the pathogen survive or even thrive in their new host, which is typically bad news for the new host.
Think of pathogens such as Ebola, rabies, HIV, SARS, and the Spanish flu, all of which are spillovers from other species, and you will understand that pathogens that have the potential to spillover a.k.a zoonotic viruses can result in disaster.
Be assured, you will learn much about these intriguing pathogens, however, this book is not just a review of what we know about zoonotic viruses. On the very first page Quammen takes us to a sunny idyllic farm in Australia. Recently a number of horses have died following under mysterious circumstances. Worse still, several humans that came into contact with the horse also died. What caused these deaths and from where did the horses acquire it? Quammen instantly grips the reader. It was an instant page turner, with real science in it! You must know how these horses and humans died and you gladly, eagerly, follow Quammen when he takes you on a journey in the scientific literature as it develops over time, with frequent field visits that Quammen personally joined to understand the subject better.

Quammen cover several different pathogens, including HIV, Ebola, malaria, and SARS, and he travels accordingly. We get to follow scientists (and Quammen) into crowded Asian markets where hundreds of different animal species, each with their own set of nished pathogens, can be bought for that evenings dinner. We get to visit Bangladesh to analyse date-palm-sap to see if bats have pooped deadly virus into this popular drink. We visit the Congolese jungle where Ebola have completely eradicated large populations of gorillas as well as some smaller human populations. We go to caves filled with snakes, bats and guano. Of course we also get to visit high tech laboratories around the world to talk to researchers who try to understand these zoonotic viruses and predict where the next big pandemic will strike - because if or when “the next big one”, capable of killing us by the millions, comes, it will almost certainly be a spillover from another species.
The human species is vulnerable. We are around seven billion people. We are an urban species meaning that we tend of cluster in large groups (cities), which provides pathogens with the perfect springboard. We travel extensively, and could thus easily spread a virus around the globe in a short amount of time. We also continually mess with new ecological systems which may or may not have a deadly virus just waiting for a new host...

Put another way. Human population growth is an typical example of an outbreak i.e., explosive population growth. Just like with outbreaks of crickets that sweep across Africa eating everything it encounter, humans are sweeping across the entire planet, interfering with lots of ecological systems along the way. Indeed the most massive outbreak of any species that the world had ever seen is not a cricket or a larva, it is homo sapiens. And when there is an outbreak of a particular species what typically halts it? You guessed it - pathogens.

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