David QuammenIntervista

Intervista con l'autore

David Quammen is the author of many articles and books on science and natural history, including The Song of the Dodo and Monster of God. Before he turned to non-fiction writing, Quammen also wrote several spy novels, including The Soul of Victor Tronko. Quammen's new book, Spillover: Animal Infections and the Next Human Pandemic, was published this month by W.W. Norton & Company.

Before we get too far, can you give us the nutshell explanation of zoonosis and spillover, for those who haven't yet had a chance to read the book? What sorts of diseases are we talking about here?

Zoonosis is an animal infection transmissible to humans. It can be a virus, a bacterium, a protozoan, a number of other infectious bugs. It doesn't necessarily cause disease in humans, but if it does cause symptoms once it gets into humans, then we call it a zoonotic disease. Spillover is the label for the moment when any sort of an infectious pathogen passes from one species into another, but we particularly think of it in terms of animal infections passing into humans.

That includes a whole rogue's list of the best-known diseases, and also some little-known things: it includes 60% of the infectious diseases that we know, under the strict definition of zoonosis. That runs from West Nile and hantavirus, Lyme Disease, all the influenzas, Ebola, Marburg, a couple of exotic little-known things called Nipah virus from Bangladesh, and Hendra virus from Australia. Also SARS, which came out of southern China, and of course HIV, the AIDS pandemic, also began with a zoonotic spillover.

You write much in the book about bats, which seem to be particularly well suited as reservoir hosts for these diseases. What is it about bats that makes them work so well for this?

First, reservoir hosts: these diseases that spill over into humans, they spill over from non-human animals, and generally they live in those non-human animals asymptomatically; they have a permanent presence there and they don't cause symptoms or disease in those animals. They just abide there quietly over long stretches of time. Those animals are known as the reservoir hosts. If they spill over from that reservoir host and they get into another animal—for instance Ebola spills over from its reservoir host and gets into chimpanzees and gorillas—it kills them also, so we know that they cannot be its reservoir host because they die from it too quickly.

There seems to be a disproportionate number of cases in which the reservoir host for one of these emerging viruses is a kind of bat, or several kinds of bats. So scientists who work on this whole subject have been asking themselves "Why bats? What is it about bats?" Are they disproportionately represented, and if so why, or do they merely seem to be disproportionately represented because bats are such a diverse taxa that it's only natural that many of these diseases come out of bats? Bats account for one in every five species of mammal, and they're a very diverse group. But the thinking, at least the lean, is toward thinking that there is something inherent about bats that might support more viruses that spill into humans. And that could be a couple of things: one, they live very sociably, piled on top of one another in colonies of not just hundreds but thousands and tens of thousands, sometimes millions in a single cave. They live very closely juxtaposed with one another, sometimes five deep: mothers and pups and other adult individuals around her. And they live a long time, much longer than any other small mammals. It's not unusual for a bat to live eighteen or twenty years. That combination of things may mean that bat colonies are particularly good incubators for viruses.

As part of the research for this book you traveled to many parts of the world where zoonotic outbreaks have occurred. Tell us about the most interesting or harrowing experience you had while on one of those trips.

I did travel a lot, for about five years. It's sort of a scientific travelogue, in roughly the same way that my book The Song of the Dodo was a scientific travelogue. I read a lot of journals, I do a lot of research in the literature, I talk to scientists, but I really like to get out into the field with scientists, experience some of what they're doing, and gather stories. So I hope there are some interesting, suspenseful, and in some cases maybe even amusing stories in this book, which otherwise is such a serious, gruesome subject. I always like going to the Congo, so being in the Congo on a research trip with a scientist who was intending to dart gorillas in order to draw blood samples to look for antibodies of Ebola, that was my cup of tea. Unfortunately the gorillas were all gone—they seem to have all died off from Ebola in the area of the forest where we were, so we didn't succeed in collecting any blood samples. But it still delivered a pretty powerful impression of them impact that virus has had, killing gorillas and chimps as well as humans.

I had a very good time in Bangladesh with a scientists named Jon Epstein, who was doing research on the ecology of the virus Nipah, which is known to have its reservoir also in bats (giant flying foxes). He and I and his crew were on the roof of a warehouse in southern Bangladesh in the middle of the night with a great big net about the size of the screen of a drive-in movie trying to catch these giant fruit bats as they came in from their evening of eating. That was a very vivid evening, and also a productive one because we caught a lot of bats and he took a lot of blood samples from them. So there were things like that, which made it an adventuresome process researching it for me and which I hope will make it a lively book for other people.

You write about some of the fascinating research that's being done—it seems almost like medical archaeology—to try and determine the histories of these diseases in humans and their animal hosts (with AIDS, for example). How is that work done, and what do you think is the most notable thing researchers have discovered so far in this field?

Medical archaeology is a good phrase, do you mind if I steal that from you? The other term for what they're doing is molecular phylogenetics. This has been very important in reconstructing some of the past history of what viruses or pathogens have spilled over, roughly where, and when. By taking viral samples and sequencing the genomes and creating family trees, cladograms in the technical parlance, of those viruses, you can learn some very interesting, significant things. For instance, where did the pandemic strain of HIV come from? Where did it spill into humans, from what animal, and when? There's wonderful work that's been done just in the last five to eight years, by a couple of scientists and their colleagues: Beatrice Hahn, who has recently moved from the University of Alabama at Birmingham, and Michael Worobey at the University of Arizona. The two of them and their colleagues have essentially answered the question where and when did the pandemic strain of the chimpanzee virus that became HIV spilled over into humans to become HIV. They've answered that with the scenario that the virus spilled over from a single chimp to a single human in a relatively small corner of southeastern Cameroon, sometime earlier than 1908, give or take a margin of error.

The book that many folks probably know on a similar topic is Richard Preston's The Hot Zone. You take Preston to task a bit in Spillover. What do you wish he'd done differently when he wrote about the Reston ebola outbreak, and what should the lesson be from that book?

Well, there are a few very specific things. I don't want to be hard on Richard; I don't like criticizing a colleague. I read that book, well first I read the two-part magazine article in The New Yorker, and to me it was just riveting. It was a wonderful piece of journalism and it certainly galvanized my interest as it galvanized the interest of a lot of other people. And then the book was a little bit different. One of the things that I think appeared in both the magazine version and the book is these two ideas, one that Ebola is an extraordinarily bloody disease, that people just bleed out, their blood just flows out of them and leaves them like husks, with blood flowing out of their eyes and their rectum and their mouth, and any needle pricks, it's just really extraordinarily bloody. And that turns out to be not the case. As a matter of fact the experts on Ebola don't even call it Ebola hemorrhagic fever anymore; they've dropped the "hemorrhagic" because sometimes Ebola is bloody and in many cases it's not. That is not an inherent, invariable characteristic of the disease, and it was exaggerated in his book and he agrees with that.

The other idea is the notion that Ebola virus somehow dissolves peoples' internal organs, and he I think describes a case where a person essentially just dissolved or melted on the inside. I'm not an Ebola expert, but I've talked to the same Ebola experts that Richard talked to, and to many others, and what I hear from them is that no, that just doesn't happen. So those two things in particular were, I think, over the top in his book, and his book was so successful that it made people think that those were characteristics of Ebola. Ebola is a horrible disease, it kills many people, it's not to be minimized, but it is not as preternatural as it is portrayed in Preston's book.

Is there more that we should be doing as a human society to prepare for another big pandemic, the "Next Big One," or is a zoonotic pandemic at some level inevitable?

Not inevitable, no, but I think it's fair to use the word probable. We are now a hugely abundant species: there are seven billion of us, and that's like looking at a very old, very, very dense, very dry forest in an area where lightning strikes are happening all the time. Is that forest going to burn? Well, probably. Likewise, we are probably going to experience another pandemic. Maybe it'll "only" be a really bad influenza, but bad influenzas can kill millions of people. So it is very likely that we'll face another one of these things. What is it likely to be? Well, the scientists I've talked to say it's very, very likely to be, first of all, a zoonotic disease, coming out of an animal. Secondly it's most likely to be a virus, and third, it's probably likely to be a single-stranded RNA virus, which means certain families of viruses represent likely sources and other families are a whole lot less likely. Why RNA viruses? Because they mutate at a high rate when they replicate themselves, creating a lot of mistakes in their genome. Those mistakes represent genetic variation, and usually genetic variation is bad for an organism, but it's also the raw material of Darwinian selection and evolution. So that amount of mutation makes RNA viruses more plastic, more protean, more changeable, and therefore more adaptable, more likely to be able to spill into a new host (such as humans), adapt to that host, and become highly successful.

Was there a particular author who inspired you as a writer?

There's one author who influenced me hugely, by far my largest literary influence and it's probably going to seem counter-intuitive, but that's William Faulkner. I started as a fiction writer, and before I was a fiction writer I was a fiction reader. I started reading Faulkner when I was a freshman in college, and became obsessed with him (like a lot of people do because he's such a great writer). I did my graduate work on structure in Faulkner's novels, and then I started my writing career publishing novels myself. I discovered that I wasn't really meant to be a novelist and I turned into a non-fiction writer. But even now, when I spend six years or eight years researching a non-fiction subject, a big sprawling topic like zoonotic diseases or island biogeography, and then the time comes to put that together into a 500-page book, or a 600-page book, what I learned from closely, closely examining and pondering the structure of Faulkner's novels serves me very, very well.

What's your home library like? What sorts of books would we find on your shelves?

Well, my house is almost completely lined with books. I built a new house about ten or twelve years ago, and one of the main reasons was that the old house wouldn't hold enough books. My office is generally lined with the books from my book projects: right now there's a whole set of shelves devoted to zoonotic diseases, there's another whole wall of shelves devoted to Darwin and evolutionary biology. There's another wall devoted to big predators, from my book Monster of God, and the books about island biogeography have sort of been pushed out into the dining room. But then there's a whole shelf, well no, there's a whole wall that's Faulkner and southern writers. Robert Penn Warren was my mentor, so I have all of his books. I've got a section of poetry, lots of biographies—I love biographies—a lot of history. I've got one wall devoted to essentially the history of espionage, because I wrote spy novels for a while before I became a non-fiction writer. So it sort of comes in clusters like that.

What books have you read and enjoyed recently?

I just finished Seth Mnookin's book The Panic Virus, I'm reading Maryn McKenna's Superbug right now. Obviously those are related to my disease interests. I finished Stephen Greenblatt's The Swerve, and that was wonderful. I loved that, and it sent me back to Lucretius, so after I read Greenblatt I reread Lucretius On the Nature of Things. I'm reading Cormac McCarthy's Blood Meridian. Not too long ago I finished Doris Kearns Goodwin's No Ordinary Time, about Franklin and Eleanor Roosevelt. I read a lot of history, not that much fiction anymore.

Can you tell us a bit about your next project?

My next duties are to get caught up for National Geographic magazine. I'm on a contract for three stories a year with them, and they've been cutting me some slack while I finished this book, so I need to go back to Africa and finish research on a story about lions for them. I'm also doing a story about the horse in Native American cultures, for which the research is mostly done. And then there will be another book project, and I think I know what that's going to be, but I'm a little bit shy about talking about it yet.

—interview by Jeremy Dibbell