What do dengue fever, yellow fever, bubonic plague, bovine tuberculosis and West Nile fever have in common? Add to them swine flu, bird flu, SARS, HIV and Ebola and perhaps it becomes more obvious: all are zoonotic diseases – those that have crossed from animals into humans, often with devastating consequences.
In 2012, science writer David Quammen tackled the subject of zoonosis in his book Spillover (which I have yet to get my mitts on). But in a clever marketing move, two chapters from the book have been republished and expanded as stand-alone books: Ebola: the natural and human history (2014) and The chimp and the river: how AIDS emerged from an African forest (2015).
I’ve devoured both books and I’m now champing at the bit to read the rest of Spillover. So take this review as based on the two stand-alone books, and presumably (though I can’t guarantee it, if course) more generally about Spillover.
Both books/chapters are part science writing, part detective story, as Quammen traces back knowledge about HIV and Ebola to try to find out where, when and how they came to infect humans. He follows the scientists’ frustrations and dead-ends in between breakthroughs; in that sense, the stories are as much about the scientific process as they are about infectious diseases. (As any scientist knows, the ‘Eureka!’ moments are few and far between, whereas the ‘dammit!’ moments are frequent.)
The writing benefits from Quammen’s first-hand experiences of the areas in question, from his travels as a National Geographic contributing writer. The sense of place comes through very strongly: these aren’t stories about some exotic location most of us will never visit. Quammen takes his reader there, doing his best to see the diseases and unfolding events through the eyes of the people at ground zero.
That’s where The chimp and the river really set itself apart. Quammen begins with “Patient Zero” as knowledge stood in the 1980s at the burgeoning beginnings of what we now know as a global pandemic. But Gaëtan Dugas, the Canadian flight attendant fingered as responsible for spreading HIV around the Western world, was never really patient zero.
Using a molecular dating method, tracking how many genetic changes separated different strains of HIV and estimating how long that divergence would take, puts the “spillover” event at about 1908, most likely in a small sliver of south-eastern Cameroon. And that’s just the strain that caused the pandemic, there are four known types of HIV-1 (including one from gorillas) and eight known types of HIV-2, suggesting, at least, a dozen spillover events from simians to humans…that we know of.
People are at the core of Quammen’s tale, whether they’re the ones we know, like Dugas and the key scientists working on HIV/AIDS research, or the ones we can only imagine, like the Cameroonian hunter who was presumably infected with a simian version of the immunodeficiency virus somewhere near the start of the 20th Century.
In his past, Quammen has also been a fiction writer and this is apparent in these books. In The chimp and the river he goes on an imaginary journey, tracing a possible route for HIV in its newly-hijacked human hosts, down the river, into larger and larger settlements. Eventually, to the world.
Of course, there’s no way to know exactly how the virus made its way from humble beginnings to global pandemic, but Quammen has given you enough background to start with to allow an imagination of “this is how is could have been”.
Between this lyrical fiction and some serious science background, including interviews with many of the major players, Quammen hits a delightful balance between informative and enjoyable reading.
Those keen for further reading will be pleased with references to specific publications, with full details in the bibliographies. Quammen’s made it easy to track back to individual researchers and scientific publications, without bogging the text down with footnotes or citations. For that reason, I think he gets away with the odd flight of fancy since it’s clear he’s done his homework and knows what he’s talking about, and it is based in solid, well-referenced science.
For the past decade or more, it has become ever more apparent that diseases crossing over from animals will be a major driver of global human health. We’ve seen SARS, swine flu, bird flu, the 2014 Ebola outbreak. This year it’s Zika virus (which Quammen has already written about).
There’s a reason we were able to eradicate smallpox: it only infected humans. But anything that can sit quietly in an animal host can spillover time and time again, reinfecting humans and spreading. Zoonosis, Quammen writes, is “a word of the future, destined for heavy use in the twenty-first century”.
If he’s right, then you could do worse than get up to speed on some of those diseases that have already broken out into the human population with devastating consequences.
Featured image: Flickr CC, Martin.