Book Review: Spillover: Animal Infections and the Next Human Pandemic

Is mankind increasingly presenting itself as a host to opportunistic pathogens? Does everything, including pestilence, come from somewhere? In what could be easily one of the best books I have read in the pop-sci genre, writer David Quammen's sprawling work Spillover, while unfolding with an urgency akin to a medical thriller, talks about zoonoses, the infectious diseases that spill over from animals to humans (or vice-versa, in which case they are called anthroponoses) and their beginnings.

The contagion
Over the course of some 520 odd pages, Quammen's globe-trotting adventures take us to Australia, where a relatively obscure virus called Hendra has jumped from bats to horses to humans, to Central Africa, where mysterious mass deaths of gorillas uncover a new primate to human transmission of Ebola virus, and to Borneo, where a particular primate malaria parasite (Plasmodium knowlesi) has been declared an emerging zoonosis.

And then we have got SARS, which "in late February 2003, got on a plane in Hong Kong and went to Toronto". This chapter notably makes for a terrifying read given how the coronavirus (CoV) swiftly gets transmitted over air. But where did the virus itself come from? Bats? Very recent research has in fact found the Chinese Horseshoe bats to carry a new strain of SARS CoV, adding weight to the theory.

Quammen soon gets taking about Herpes B virus, jostling through the crowded streets of Bangladesh (and assisting field experts in trapping monkeys) in an attempt to better understand the virus that causes severe neurological dysfunction or, at times, even death in humans. There have been (only) 26 documented cases so far worldwide, 16 of them reportedly leading to death.

Tracing the origins and spillovers of Nipah and Marburg viruses in subsequent chapters, Quammen interestingly veers off to explore a few bacterial zoonoses like Lyme Disease, Q-fever and Psittacosis or Parrot Fever before turning his attention back on AIDS virus, outlining the putative path of HIV-1 (which we know to have come from our primate ancestors, the chimpanzees) and its less virulent variant HIV-2, both of which emerged in Africa at the start of the twentieth century.

Spillover gets a topical touch when Quammen goes on to expound the emergence of Influenza A virus, the infectious agent responsible for recurring outbreaks of swine and avian flu in China and other countries. What's more, in the closing chapter, he describes a sudden population boom of tent caterpillars in his home town in 1993. "There were simply too many, and the infestation proceeded along its inexorable course."

Then something happened. The caterpillars were gone, their entire population completely wiped out. Years down the lane (as part of researching for this book), he learns that it was a pathogenic virus that led to the population collapse. Will humans too suffer a similar predicament? We, who are the single most dominant species on earth, are "grotesquely abundant" much like the tent caterpillars, Quammen writes.

Our activities have drastically altered the ecology of our surroundings; we cut our way through forests and several other natural habitats, disturbing the balance of species in the ecosystem, and as wildlife becomes scarce, the abundant human population serves as an ideal opportunity for more spillovers. Even if we can't predict the next big pandemic (or the Next Big One), Quammen rounds off by saying that it is necessary to be forearmed and be "well-prepared and quick to respond" through scientific means.

Simply astounding for the sheer breadth of topics covered, extremely well researched (the chapters on Ebola and HIV bear testimony to this), morbidly entertaining and above all, eloquently written and compellingly narrated, Spillover is an incredible and a must read. Just think of a real life version of Steven Soderbergh's 2011 Hollywood film Contagion. That's this book in short for you. Now if you will excuse me, I need to pick up his other books!