Eight years ago, in 2012, author and science writer David Quammen wrote in his book Spillover that a future pandemic, the Next Big One, would be caused by a zoonotic virus, coming from a wild animal, most likely a bat, and that humans would come into contact with this animal in a wet market in China.
Quammen didn’t foresee the future, he studied the scientific data and researched and reported on the history of epidemics. From his home in Montana, Quammen answered some of our questions to help us better understand the current pandemic. In this interview, we take a deeper look at the causes, the dynamics and the consequences of the coronavirus pandemic. It’s edited slightly for clarity.
How does spillover happen?
Spillover is the term that applies to that moment when some sort of a virus or another disease causing microbes passes from its non-human host into its first human host. That’s the spillover. And so the first human host is like patient zero. And the diseases that do that are called zoonotic diseases. The virus itself, we call zoonosis. So spillover is when a zoonosis passes from its reservoir host where it lives permanently and inconspicuously without causing disease, usually, in some kind of a nonhuman animal. When it passes from that nonhuman animal into its first human victim: that’s spillover.
One of the sections of your book is entitled “Everything comes from somewhere.” So why and how is it that human destruction of biodiversity or human interference in the environment creates the conditions for new viruses like this current virus to arise?
Our diverse ecosystems are filled with many, many different kinds of species of animals, plants, fungi, bacteria, other forms of biological diversity, other living creatures, all cellular creatures. A virus is not a cellular creature. A virus is just a strip of genetic material inside a protein capsule. It’s sort of a mechanical parasite upon cellular creatures, it can’t reproduce itself independently, it can only reproduce itself by getting inside a cellular creature and using the machinery of that cell to manufacture its own proteins, manufacture its own genome and multiply into hundreds of viral particles and then come bursting out of that cell.
So our many species of animals that live in diverse ecosystems all carry their own unique forms of virus. We don’t even know how many viruses live in the animals of the Congo forest or the animals of the Amazon. We don’t have any idea. We just know it’s a lot of diverse viruses. And so when we humans disturb those diverse ecosystems, when we go in there and cut down trees and build timber camps and build mining camps and catch the animals, kill them for food to feed the workers or kill them for food to transport somewhere else and sell in a market, or even capture them live to transport and sell in a market, we bring ourselves closely in contact with those animals, we disrupt those ecosystems and we shake loose, in effect, new viruses. We offer those viruses the opportunity to seize on a new host. And there we are as the potential new host. So the viruses infect us.
And then because there are so many of us and we are so closely interconnected — 7.7 billion humans on the planet now flying around in airplanes every which way, transporting food, transporting other materials — if these viruses take hold in a human, if they can replicate in a human, if they evolve so that they can transmit from one human to another, then they have won the sweepstakes, or as one scientist put to me, they have won the golden ticket because now the host that they’re in is the most abundant large animal host on the planet. They can go everywhere and can infect millions and millions of people. And that’s what happens. And that’s the root cause of spillovers and the root cause of the problem of zoonotic diseases becoming global pandemics.
Does the distinction between zoonotic and non-zoonotic diseases help explain, in any way, why humans have conquered certain diseases and not others? In other words, is it harder to cure zoonotic diseases? And if so, why?
Yes, that’s a good question. You’re exactly right. Sixty percent of human infectious diseases are zoonotic, meaning the virus or whatever causes them came from a nonhuman animal in relatively recent times. We know what happened and we can trace it with scientific research and say, “this virus came from that kind of animal.” The other 40% of human infectious diseases had to come from somewhere. So because we are a relatively young species most of our infectious diseases are caused by viruses or other pathogens that are slowly evolved versions of other things that came from some other species a long time ago, maybe thousands of years ago. But if they are now in the present, not zoonotic, meaning that that is a virus that is only adapted to us and it doesn’t live in other animals, then yes, we can eradicate it.
For instance, the most famous case: we have famously eradicated smallpox, and it exists now only frozen in some research laboratories. It doesn’t circulate in the human population. Why have we been able to do that? Because it doesn’t live also in animals. If smallpox lived also in some kind of a bat or some kind of a monkey, then we couldn’t get rid of it in the human population unless we also got rid of it in that animal population. We’d have to either kill all of those bats or cure them of smallpox also. That’s why we can eradicate a disease like smallpox, and that’s where we can never ultimately probably eradicate a disease that is zoonotic unless we kill off the animals that it lives in.
So what’s the solution if a virus comes to us from bats? Should we kill off all the bats? No, that’s not the solution. The solution is we should leave bats alone, because we need bats and our ecosystems need bats.
My next question was going to be about bats. Is the fact that bats and humans are both mammals relevant? Does this make it easier for the virus to spillover?
It probably does make it easier, the fact that bats and humans are both mammals. Many of the viruses that caused spillover and zoonotic disease in the last 60 years have their reservoir host in bats. But why bats? Why do bats seem to be overly represented?
Well, first of all, bats are mammals like us. So the viruses that are adapted to them are more likely to be able to adapt to us than a virus that comes out of, say, a reptile or a plant. Second reason is that bats are overly represented in mammal diversity. One quarter of all species of mammal on the planet are species of bats — 25%. So they’re overly represented in mammal diversity and therefore it’s natural that they seem overrepresented as sources of viruses that get into humans.
There are another couple of things beyond that that also make bats more likely candidates and sources. Bats live a long time, and they tend to roost in huge aggregations. In a cave, there might be 60,000 bats in a big knob roosting together on the wall of a cave. And so that’s a good circumstance for passing viruses from one individual to another and for viruses to circulate through the population. There’s one other thing that scientists are just starting to research and that is that bat immune systems may be more tolerant of “strangeness” in their bodies than other immune systems.
From what I understand epidemics are not independent from one another, they’re all connected, because these viruses are recurring for the reasons that we’ve talked about earlier. So where do these viruses go when they’re not directly threatening human beings?
This pandemic is so broadly spread it may not disappear, but let me take a different example. Ebola in 2014. There was a big Ebola epidemic in West Africa, in Guinea, Sierra Leone, and Liberia. We still don’t know the reservoirs but we suspect bats. Ebola disappears for years at a time. It goes away. It comes out in an outbreak and it kills hundreds or thousands of people and healthcare workers and scientists respond to it and they finally slow down the outbreak and stop it, and then it goes away. Where does the virus go? Is it gone? No, it’s still in its reservoir host. Viruses from people don’t go back into the reservoir host, but the virus has continued to live quietly in the reservoir host. So when it’s eliminated from the human population, as Ebola can be eliminated from the human population, it continues to reside in its reservoir host somewhere in the African forest.
And that’s what happens with most of these outbreaks. They come, they affect humans, people suffer, people die, healthcare experts and workers respond. It’s brought under control, the epidemic disappears and then a number of years pass before it happens again. Where’s the virus in the meantime? It’s in the reservoir host.
Is there a correlation between higher rates of pollution in certain areas and a harder impact of the virus on the population of that area?
Yes, I think there could be a correlation between air pollution and damage to people’s lungs and respiratory tracts and how susceptible they are to this particular virus. I think that’s an important question. I don’t think we have answers to that yet, but is that a question that deserves research and attention? Yes, absolutely. It’s entirely possible that the damage to people’s lungs, even if it’s not noticeable to them in normal times, it might be there and might be sufficient to make them more vulnerable to this virus.
I’m going to ask you the big question that many in Italy are asking themselves at the moment: why is it that Italy is having such a high lethality and case rate compared to other countries?
I don’t know why. I’m asking myself the same question. The fact that this spreads silently, it spreads invisibly from people who don’t know that they’re sick and who don’t feel sick makes it possible that maybe just one person brought it in and then it circulated in Northern Italy for a couple of weeks and a lot of people got infected before the first alarm bell rang.
This is another element to this virus that is interesting: symptoms arrive later on. So there’s no alarm from the organism that says: “you’re infected.” Does this make it more dangerous compared to other diseases that show symptoms much earlier?
It absolutely makes it more dangerous. I think I said in Spillover that we were lucky with SARS because even if SARS was a very dangerous virus and it spread easily from human to human and it had a high case fatality rate, almost 10%, it would have been much worse if people were shedding virus before they were feeling symptoms. There were other problems with SARS, but that generally was not the case. And I said, “God forbid that we have a virus as bad as SARS that also spreads from people before they feel symptoms.”
Right now we have exactly that virus case. Fatality rate is not as bad, although in Italy it’s close to that bad. But you know, they say when a bullet hits a soldier, you never hear the shot from the one that gets you because the bullet gets there first and then the sound gets there after. This virus works like that.
A lot of my work is focused on climate change and climate disinformation. I was trying to keep track of scientific disinformation with the spread of this virus and there are definitely some points of contact between the two mechanisms of disinformation. What’s your opinion on this? And how important is it to address scientific disinformation?
It’s hugely important to address scientific disinformation. I’m glad to hear that you’re doing that in connection with climate change. There absolutely is an overlap. There are people out there who are impatient, angry and people who aren’t very well-informed. They get their news from unreliable news sources, and they have an appetite for negative excitement. They have more interest in conspiracies than they do in science. Certain kinds of people prefer that sort of explanation because it’s more satisfying to their prejudices. And disinformation spreads easily.
What is the threshold between offering accurate, credible, transparent news accessible to everyone and hounding people with “news” about the virus 24/7?
Yes, there is a threshold there. There can be too much of it. And now we live in a world where the electronic media is on 24 hours a day and they want updates, they want eyes, they want people to turn to their channel because their channel has got something a minute before the other channel has. So there’s that kind of competition that doesn’t do anybody any good — except the stockholders of the channel.
So I think we, as consumers of news, we need to resist being obsessed with what’s the latest number, what’s the latest case, what’s the latest breaking news. We need to follow that, pay attention to some of that. But we need other things. We need coronavirus stories that go deeper into cause and effect into what can be done. And we need stories that are not about coronavirus. We need music, we need comedy, we need arts, we need people talking about books — and not just my book.
How does fear play into this kind of scenario, into collective behavior during a pandemic? Is it negative? Is it positive? Or is it just human?
Fear is very human. Fear is natural. Panic is also a human. But they’re not useful, nor helpful. People ask me sometimes, well, there’s this new virus coming out of China. How scared should we be? And I want to respect that question, but I generally say it’s the wrong question. Because being scared, being worried is not going to do you any good. So learn more about this virus and then take measures and help society take measures to control it.
We have to be very careful that social distancing does not lead to emotional distancing and that we start to look at the other person as a threat or an enemy. Stay healthy and do the social distancing and we’ll get through this. But it seems to me that the fear of the other person is something we have to be very careful of or it will sicken our culture and our societies as badly as this virus is doing. So social distancing yes, but emotional connectedness.
What can we learn from this pandemic?
Well, first of all, we can learn that zoonotic diseases can be very dangerous and very costly and we need to be prepared for them. We need to spend the money and exert the will when the pandemic is over, before the next one happens. We need to spend a lot of resources and a lot of attention on preparedness. More hospital beds, more intensive care units, more ventilators, more masks, more training of healthcare workers, more training of scientists who study these things. Emergency plans at the local level, the provincial level, the national level for dealing with this, all of that costs money.
The other thing that we need to learn is that the way we live on this planet has consequences, negative consequences. We dominate this planet like no other species has ever dominated this planet. Hooray for us! But there are consequences and some take the form of a pandemic of coronavirus. This is not something terrible that just happened to us. It’s a result of things that we do, the choices that we make. There’s enough responsibility to go around to everybody. We need to understand that.
Obviously no one really knows the answer to this, but how do you see the world after coronavirus? What’s going to change for societies? What’s going to change in people’s lives?
Well, I hope then even people like Donald Trump will learn the hard way that these things have to be taken seriously. We have to make adjustments. It may be we will start to reduce our impacts in terms of climate — all the fossil fuels that we burn — in terms of destruction of biological diversity, invasion of the diverse ecosystems. Maybe we will start to step more carefully and more lightly on this planet. That’s what I hope and that’s the only good that can come out of this experience.
