David Quammen, “Spillover: Animal Infections and The Next Human Pandemic” (2012)


Much like his last book, Monster of God, David Quammen’s Spillover is a chronicle of the ways human and non-human animals interact, and the implications therein. In the case of Spillover, the subject is zoonoses, infectious diseases that cross over from animals to humans – a more modern-leaning subject than Monster of God, but one that still encompasses some of the major ongoing events in recent human history. The constant struggle with diseases like ebola and AIDS and the more recent stories of SARS and avian flu often become background noise after a brief period of hubbub, but their shadows always loom – they are problems that seem to be the eternal foes. These diseases seem to be the issue the world does not want to talk about, and as the subtitle suggests, it’s the one that always has the possibility to return to the forefront. There is, then, an initial urgency to the way the book explores all these different events, trying to find any threads to connect them, and possibly find answers to what’s next and what we could do about it.

Quammen’s books tend to lavish equal attention to both animals and the humans that interact with them on a regular basis, using these stories to uncover the convoluted ways the natural world functions, and Spillover is no different. The victims of the diseases, their loved ones, and the scientists who have ongoing missions to research those same diseases in a multitude of fields are all provided with their own individual stories, portraying the broad ways these epidemics affect people, right alongside the naturalist reports on how infections originate and affect their animal sources. Bot kinds of narratives are important, as the way the diseases ultimately come to their apex is through a the complicated movements of all species involved – viruses transferring from one species to another, sometimes amplifying the infectiousness, and then brought into contact with humans through various means. Usually, those means come back to us – we take up the land and force the movements of species, we find new animals to turn into pets or gourmet items, and while not mentioned as much in this book (but still set up as an explanation) there’s the changes imposed by climate change as well. Sometimes, too, these interactions are ancient, but have only recently began spreading illnesses, or the illnesses have only recently (historically-speaking) become potent in humans – giving the whole thing a sense of inevitability. Just like how violent encounters between humanity and alpha predators are unavoidable while they share space, so will germs be shared as we come in close proximity with other species.

All of these elements contribute to one of the other recurring themes Quammen sees in these stories – that trying to predict the emergence of these diseases may be impossible, given the level of complexity of their transference between species, and the chance alignment of factors that allows them to flourish. Every section seems to leave you with as many questions as answers – the diseases are ongoing cases that flare up and disappear over periods of years, and so investigators only real have so much time to figure out what’s going on. While the animal sources of the germs are sometimes found, it is difficult to tell if something is the point of origin or simply the current reservoir host – the cases of both SARS and Lyme Disease show how sources can be misidentified or shown to be more complex than originally thought (that many of these diseases have bats as reservoir hosts on several different continents is a inconclusive thread in itself.) In cases where the reservoir host is found, there are questions that remain – for example, why certain people are infected while others are not, or why only certain animals show symptoms. The possibility of infection and increased virulence among humans (and its the idea of humans being able to pass these infections to each other is treated as the real turning point) is itself highly convoluted, with cultural practices both ancient and modern suddenly allowing the viral invaders in, and the interconnectedness and access to long-distance travel bringing those same microbes all over the world all made to be major components of the pandemic process. The survival of these diseases is predicated entirely on travel, from within and without a species, and we are in a special position in this age to give them opportunities never before possible. But that’s real all we can say for certain – it’s a possibility.

Going back to the subtitle, there can be no real prediction of the next “Big One” – while we are knowledgeable about several candidates, and have been making preparations to deal with them, there’s really no telling if one will re-emerge, or if a new one will suddenly appear somewhere in the world, or if a previously benign one suddenly be amplified. The way organisms act and react is incredibly chaotic, and one change in the environment or chance quirk of evolution can create an unexpected chain reaction. This is very well demonstrated by the very nature of the RNA viruses, which the book goes back to repeatedly as the source of some of the most devastating zoonoses – their ability to adapt to new hosts relies on their decidedly unstable genetic coding, which often produces rejects, but can also allow them to change in highly beneficial ways (highly beneficial to the virus, that is.) A simple rearrangement in the building blocks of life, and a common virus in wild primates suddenly becomes HIV. Life is never very conducive to our attempts to understand it.

But, all that said, the book never turns fatalistic – as mentioned, we can use the knowledge we have gathered to help us contain or control future outbreaks. The oft-referenced equation that determines such outbreaks in populations is never refuted, but simply has the aforementioned complexities factored in. As one of Quammen interviewees states, humans themselves can be considered an outbreak – our numbers having exploded in recent years – and, much like the viruses, have a great ability to adapt to circumstances.


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