'Pandemic' Asks: Is A Disease That Will Kill Tens Of Millions Coming? | KUOW News and Information

'Pandemic' Asks: Is A Disease That Will Kill Tens Of Millions Coming?

Feb 22, 2016
Originally published on February 23, 2016 2:32 pm

As public health officials struggle to contain the Zika virus, science writer Sonia Shah tells Fresh Air's Dave Davies that epidemiologists are bracing themselves for what has been called the next "Big One" — a disease that could kill tens of millions of people in the coming years.

Citing a 2006 survey, Shah says, "the majority of ... pandemic experts of all kinds, felt that a pandemic that would sicken a billion people, kill 165 million people and cost the global economy about $3 trillion would occur sometime in the next two generations."

In her new book, Pandemic: Tracking Contagions from Cholera to Ebola and Beyond, Shah discusses the history and science of contagious diseases. She notes that humans put themselves at risk by encroaching on wildlife habitats. "About 60 percent of our new pathogens come from the bodies of animals," she says.

Shah adds that international travel is also a factor in the spread of disease. "Air travel shapes our epidemics in such a powerful way that scientists can actually predict where and when an epidemic will strike next just by measuring the number of direct flights between infected and uninfected cities," she says.

Looking toward the future, Shah says that epidemiologists can do more to identify potential outbreaks before they happen. But eliminating them altogether is another matter. "Our relationship to disease and pandemics is really ... part of our relationship to the natural world," she says. "It's a risk we have to live with."


Interview Highlights

On our first response to new pathogens

A lot of times when we talk about being more prepared in preventing pathogens from spreading or preventing pandemics, what we're really talking about is first response, stepping up our first response, so that when we have outbreaks of disease that our hospitals are prepared and we have vaccines stockpiled and we are able to fly our experts around really quickly to get to the scene of the outbreak, and things like that. But that's not actually preventing these pathogens from emerging and from causing outbreaks. That's kind of after the fire has started, then we rush in with our fire extinguishers.

But to really prevent them would mean stepping it way farther back, and that is possible now, because ... we know there's certain places that have higher risk of pathogens emerging, and we can do kind of active surveillance in those places by mapping the microbes that are there, by surveilling people or animals who are more likely to spread or to have spill-overs of microbes into their bodies. ... We have more advanced detection capacity now with genetic analysis and other kinds of ways that we can see where these invisible microbes are spreading and changing.

On how most of our pathogens come from animals

From bats, we got Ebola; from monkeys we got HIV, malaria, most likely Zika, as well; from birds we got avian influenzas, all other influenzas as well, West Nile virus, etc. So it's when we invade wildlife habitat or when we disrupt it in ways that brings people and animals into close contact, that their microbes start to spill over and adapt to our bodies.

On how Zika emerged

I think Zika is a great example of how new pathogens are emerging today. It came out of the bodies of animals; for many years, we had Zika virus in the equatorial forests of Africa and Asia. It mostly infected monkeys and possibly other creatures, too, but it very rarely came into humans. ...

We don't know what the triggering event was that allowed Zika virus to start spreading into humans, but we do know what it exploited — and it exploited two things that a lot of other pathogens have exploited, too, which is urbanization and flight travel. So in the 1940s and '50s and '60s when we had Zika virus in the forests of Africa, it was carried by a forest mosquito and that mosquito very rarely bit humans, it mostly bit animals, which is why we didn't have a lot of Zika virus in people, at least it's one reason why.

What we're seeing now is Zika virus has crossed over into a mosquito called Aedes aegypti, and this is a mosquito that has expanded its range over recent years as we have urbanized. It specializes in living in human cities. It loves garbage, it can breed in a drop of water in a bottle cap ... and it only bites humans.

So once we had Zika virus coming into Aedes aegypti, this highly urbanized mosquito, that's when we started having this explosive spread. Of course, it traveled from Asia. It came out of Africa. It came into Malaysia, and then probably into the Philippines, Micronesia and French Polynesia. And that was the sort of slow spread, but then the rapid expansion happened when it came from French Polynesia into Brazil, and that was almost certainly through a flight, either people from French Polynesia coming to Brazil for the World Cup or possibly an international canoe race. But whatever it was, it was on a flight that it came over, and from there it's able to access these huge, highly urbanized populations and have no immunity, and that's what created the epidemic.

On the evolution of antibiotic-resistant bacteria

We've known since antibiotics were first developed that if we use them in ways that were not medically necessary that it would lead to the evolution of resistant bacteria. And yet, in this country, 80 percent of our antibiotic consumption is not medically necessary, it's done for commercial reasons.

When we have livestock farmers giving antibiotics in low doses to their animals because it fattens them, it helps them gain weight faster and that gets them to market faster, so this is a commercial use. And that's the vast majority of the antibiotics that are consumed in this country are for that reason. ...

We've known this for years and we do have an increasing problem with antibiotic-resistant pathogens, which is a very serious problem where we're running out of these drugs to treat these runaway infections, and we're on the cusp of entering an era when we have no more antibiotics that work for some of these bugs. ...

We need to use antibiotics more rationally. We don't do that now. That's sort of the hardest part of it that we need to do. But the other part of it is we also need to develop new antibiotics to keep up — these pathogens are always going to evolve resistance eventually, so we always need to come up with new weapons to fight them.

On why incidents of Lyme disease are increasing

Lyme disease is caused by a bacteria that lives in rodents and is spread by ticks. Now in the intact northeastern forest where Lyme disease first emerged, there used to be a diversity of different woodland animals there, like chipmunks and opossums as well as deer and mice and other things, but as we spread our suburbs into the northeastern forest and we kind of broke up that forest into little patchworks, we got rid of a lot of that diversity. We lost chipmunks, we lost opossums, and it turns out that those animals actually control tick populations. The typical opossum destroys about 6,000 ticks a week through grooming, but the typical white-footed mouse, which is what we do have left in those patchwork forests, a typical mouse destroys maybe 50 ticks a week. So the fewer opossums you have and the more mice you have, the more ticks you have and the more likely it becomes that this tick-borne pathogen will spill over into humans. And that's exactly what happened with Lyme disease and now with many other tick-borne illnesses as well.

On what scares virologists most

Novel forms of influenza are what really keeps most virologists up at night, because we are so good at spreading those around quickly, and it happens every year. We have a flu pandemic every year, and now we're hatching all kinds of new kinds of flu viruses, mostly in Asia, and then they're spreading across the globe, and we don't have immunity to some of those. ...

Right now, a typical flu virus, the seasonal flu, will still kill a lot of people every year and it's a real drain on our global economy. But we kind of put up with that, so if you had a new flu virus that even had a slightly higher mortality rate, you could see a lot more death and destruction because so many people get the flu. Think about the 1918 flu, which killed maybe 100 million people, maybe more, estimates vary, but certainly huge numbers of people died from that flu. The mortality rate was like 1 percent, which isn't huge. It sounds like a small number, but when you think about how many people get the flu, that adds up to a huge number of deaths. So these new kinds of influenza, I think, are what virologists are most fearful of.

Copyright 2016 Fresh Air. To see more, visit Fresh Air.

Transcript

DAVE DAVIES, HOST:

This is FRESH AIR. I'm Dave Davies, in for Terry Gross who's off this week. If you've followed stories about the Zika virus, you know how public health officials are struggling to understand and contain the infection. You might've missed the news from Argentina where thousands have been stricken by an outbreak of dengue, which is spread by the same mosquito that carries the Zika virus. Our guest, science writer Sonia Shah, says contagious diseases are spreading with increasing frequency in a world where international travel is common and our interaction with the natural world brings us into contact with pathogens carried by animals for centuries. Shah explores the history and science of infectious diseases in a new book which notes that specialists in infections see the real possibility of an international pandemic which could kill tens of millions in coming years. Sonia Shah's writing on science, politics and human rights has appeared in The New York Times, The Wall Street Journal and other publications. She's written three previous books. Her latest is "Pandemic: Tracking Contagions, From Cholera To Ebola And Beyond."

Well, Sonia Shah, welcome back to FRESH AIR. This book is about the spread of pathogens, and your experience isn't just through reporting on it. You tell us that you and your family had some direct contact in 2010. You write that your sons had scabs on their legs, one particularly nasty one on a knee. What was happening?

SONIA SHAH: Well, we didn't know at first. First he had a Band-Aid on it so we just ignored it for a few days, as parents of adolescent boys will do, and then he came downstairs sort of limping. And we thought, he's exaggerating, but then of course we took the Band-Aid off and looked, and the scab had erupted into these sort of little mountains of lesions, you know, they were swollen full of pus. There was maybe five or six of them under that Band-Aid. So we took him to the doctor. Anyway, turns out he had MRSA, which is a relatively new pathogen. It's highly antibiotic-resistant. MRSA stands for methicillin-resistant Staphylococcus aureus, and it, you know, causes mostly soft tissue infections but it can also get into your bloodstream in which case it can actually even kill you.

DAVIES: Both sons got it. Did it infect you?

SHAH: It did. We took many precautions to prevent that from happening including taking baths in bleach and, you know, boiling everything and doing, you know, tons and tons of laundry, but this pathogen is very persistent and it can stay on surfaces for weeks and months. And then of course, we're living in family so you end up sort of touching each other, and I got it about a year after he did.

DAVIES: And what were the effects on you and the kids?

SHAH: It was - it's a pretty localized infection for us so we would have, you know, an eruption of boils and they'd kind of come up in random places, like, really unexpected. And when you had them, it would last for a few weeks, you know, slowly get more and more painful. And, you know, depending on where it was, it would sort of debilitate your movement in some ways. Like, I would get a lot on my legs so it would be hard to drive, it would be hard to bend down, sometimes it was hard to walk. But they passed over time. You know, we first started fighting them with lots of antibiotics and getting them lanced and doing all this stuff with - you know, going to the doctor for them all the time, and then it turned out that if you just sort of stopped everything, they kind of went away on their own.

DAVIES: After five years, do you and your sons still have MRSA? Does it affect your lives?

SHAH: We do still have MRSA, and I think we might always have MRSA? It's not really known, and this is sort of the problem with these, you know, new diseases - like, whether it's going to come back and be a problem again. If we had surgery, if we had, you know, an accident, would it spread to other parts of our body? It's like, we really don't know the answers to those questions. For now we're fine, and, you know, this is the world we live in. So it's just a risk you have to live with.

DAVIES: And remarkably, that's not the only well-known pathogen that you had personal experience with in your family - also the H1N1 virus. What happened there?

SHAH: Well, it was really the fact that all of these things were happening right next to each other. So 2009, we had the H1N1 flu pandemic, and this was a novel strain of influenza that came out of Mexico and then kind of washed over the globe. It caused a lot of disease especially in young people. So my kids were - you know, they came down with it 'cause there wasn't enough vaccine at the time. This was a common experience - everyone was lining up for the vaccine, and we had shortages that year.

DAVIES: It was prevalent at your kids' school, right? So you knew there was a risk. You wanted a vaccine, you couldn't get it. Right?

SHAH: That's right. And - and, you know, and I think that's really typical of these emerging diseases, that they kind of take over really quickly - much faster than we can respond. So - and that's what happened with H1N1, for sure. My kids - the entire soccer carpool, you know, they all had had it and it just kind of washed over us. And, you know, and we see this happening with lots of new kinds of influenza pandemics that we're seeing today.

DAVIES: OK. You say washed over you, but they got a high fever, right? They were sick.

SHAH: They were very sick. They had a really high fever and, you know, just out of it for days. And the thing that's so striking about these new pathogens - especially for me. You know, I'm the daughter of two doctors and really grew up with this feeling like medicine can cure everything, you know? There's always something you can do with some kind of medicine, some kind of treatment. But with these novel pathogens there often is nothing. And so that was - I think the most striking thing about that experience is the kids were so sick and there was really just nothing you could do. There was - you just had to kind of hope that they got through it. And, you know, they did.

DAVIES: Now, we've seen these infections grow as humans have interacted more with the animal world historically. And of course as industrialization changed, the environment and we had a lot more contact with each other. And one of the pathogens you write a lot about is cholera. First of all, what happens when someone is attacked by cholera?

SHAH: Well, this is a very, very virulent pathogen. It lines the interior of your gut and it actually reverses the normal functioning of that organ so that instead of nourishing the tissues with fluids, it actually extracts fluids from the body and expels them in these uncontrollable floods of watery diarrhea and vomiting. And a person with cholera can actually lose up to 15 liters of fluid a day, and this would kill you - this can kill you so fast, it can happen within hours. And the way it actually kills you is it dehydrates you. So - which also means that the cure for cholera is relatively simple - you have to rehydrate the person.

DAVIES: So a saline solution intravenously does the trick?

SHAH: Yes, and even orally now we can get mortality from cholera down to like, 1 percent. But that's just recently. So we had several hundred years of cholera pandemics when we didn't have anything much to do to help people with it.

DAVIES: Which killed millions. It's interesting that we now know that cholera existed for centuries without ever making a human being sick. Tell us where it was and what changed?

SHAH: So cholera bacteria actually is a normal inhabitant of marine environments. It lives in coastal areas and estuaries, particularly places like the Sundarbans, which is a giant wetlands where the rivers of South Asia empty into the Bay of Bengal. And the water there is - you know, it's half salty, it's half fresh, it's relatively warm. And the bacteria grows in that water and it actually lives in conjunction with zooplankton and performs a kind of useful ecological function in that habitat by helping to recycle nutrients. So for a long time people didn't live in places like the Sundarbans, of course, because they're covered in mangrove swamps and they're tidally flooded twice a day. There are cyclones, there's tigers. But then that all changed in the 19th century when the British Raj decided to cut down the mangroves and turn them into rice fields, and that's when this bacteria started to adapt to human bodies and become the pathogen we know as cholera today.

DAVIES: So what you have here is a pathogen that existed for - gosh, who knows how long - centuries, millennia, and then at some point it migrates to humans. And this is something that you write about a fair amount, that there are a lot of these pathogens that migrate from the animal world to humans. Do you want to give us another example?

SHAH: So we've gotten - about 60 percent of our new pathogens come from the bodies of animals and they spill over into our bodies, and we have, you know, novel intimate contact with them. From bats, we got Ebola. From monkeys, we got HIV, malaria, most likely Zika as well. From birds, we got avian influenzas, all other influenzas as well - West Nile virus, et cetera. So, you know, it's when we invade wildlife habitat or when we disrupt it in ways that brings people and animals into close contact that their microbes start to spill over and adapt to our bodies.

DAVIES: We're speaking with Sonia Shah, she is the author of the new book "Pandemic." We'll continue our conversation in just a moment. This is FRESH AIR.

(SOUNDBITE OF MUSIC)

DAVIES: This is FRESH AIR. And if you're just joining us, we're speaking with Sonia Shah. She's a science writer and is the author of the new book "Pandemic: Tracking Contagions, From Cholera To Ebola And Beyond." You have a chapter called "Locomotion," which is about how modern methods of travel - or even not so modern ones - have assisted the spread of pathogens. How big of a factor is that? Let's take air travel today.

SHAH: I mean, air travel shapes our epidemics in such a powerful way that scientists can actually predict where and when an epidemic will strike next just by measuring the number of direct flights between infected and uninfected cities. And they've made these beautiful maps where you can - you know, if you mapped all the cities in the world according to the direct flights that connect them and you kind of plotted a flu pandemic, for example, on a map like that, it really resolves into this, like, perfect series of waves because the flight network is what shapes the way these pathogens spread. It's just a really effective way of spreading disease around.

DAVIES: And in the past, canals, rail lines, all of it...

SHAH: I mean, canals...

DAVIES: ...Spread disease.

SHAH: ...Were huge for cholera. I mean, for a waterborne disease like cholera, canals were kind of perfect because of course, you know, people traveled along these waterways. But the bacteria itself could persist in certain waterways, too. The Erie Canal now is a great example. It opened in 1825, and that was just in time for cholera to spread from Paris and London over the Atlantic. And then through the Erie Canal, it came into New York City, caused explosive epidemics there again and again. And then really kind of - you know, the Erie Canal connected all of the Atlantic shipping with the interior shipping, all the shipping of the Mississippi Valley. So just by connecting these two major water networks, you know, it created this kind of highway that cholerae vibrio - the cholera bacteria traveled again and again.

DAVIES: You know, you write about the factors that hasten the spread of viruses - you know, crowded living conditions as the Industrial Revolution brought people into, you know, tightly-packed communities, political corruption that often undermined plans for better sanitation and drinking water. But what was really fascinating saying to me was the way prevailing medical theories at the time about the nature of human illness made medical practices not just ineffective but positively harmful, catastrophically harmful. Let's - first of all, explain how the Hippocratic approach to medicine at the time and how it explained human illness, in particular cholera.

SHAH: So the paradigm in Western medicine at the time, which had been in place for thousands of years was that diseases like cholera were spread through miasmas. And these were essentially bad smells that rose up from decaying organic material or, you know, putrefying material, things like that. So if you inhaled a miasma, that's what would make you sick.

DAVIES: Right.

SHAH: So that was the idea. It was like smell, stink, so you have to avoid smelly things. You know, people walk around handkerchiefs on the noses and they would, you know, do whatever they could to get rid of smells. But they didn't necessarily care about the thing that was making the smells, which is, you know, in a lot of cases actually what was making people sick.

DAVIES: Right, so they didn't realize it was something you were ingesting. It was something you were breathing, they thought. What treatment and prevention practices arose from that misunderstanding?

SHAH: Well, probably the worst one was the spread of water closets, or what we now call flush toilets, where people started installing these in the 1800s. And it was thought to be healthful because it would get rid of the bad smells of human waste, right? So you don't have - instead of having, like, a privy vault or, you know, an outhouse, you would actually have, you know, a toilet that would wash the stuff away. So you wouldn't have the smells in your house and in your streets. But since all they cared about was the smell and not, you know, the contents of the toilets themselves, they didn't care that the contents were being dumped straight into the drinking water. And so this happened, you know, repeatedly in London, for example, where after every cholera outbreak, people actually installed more toilets instead of fewer and dumped more of their human waste into the drinking water because that's what they thought - you know, they thought getting rid of the smell is what would make them more healthy.

DAVIES: So wastewater into the drinking water was actually considered a public health measure.

SHAH: That's right. And they actually - they even measured that. They would measure how much sewage they were dumping into the river and - you know, and kind of celebrate that as, like, look at what a good job we're doing. We've dumped even more of our waste into the river. Therefore, we're going to be protected from these diseases in the future. And of course, that turned to not be true.

DAVIES: How did this affect the way they treated patients with cholera?

SHAH: So at the time, they thought that miasmas poisoned people with cholera, right? So you would breathe in the miasma and you would have this effect of being, you know, toxic because of the poison of the miasma. And so when people are poisoned, of course, they vomit or they have diarrhea. And that is the body's way of kind of expelling the poison. So doctors at the time thought well, this the same thing with cholera. You know, miasma has poisoned the patient and therefore we should encourage more vomiting and more diarrhea. So the exact thing that was killing people, which was the desiccation from this, you know, vomiting and diarrhea is what doctors at the time would try to encourage. And so they would do all kinds of things to make people vomit more, have more diarrhea. And so they basically, you know, hastened their death.

DAVIES: You know, what's interesting about this is it's not just that, you know, physicians, they didn't know what they didn't know but their commitment to this thinking blinded them to real empirical evidence that would've made a big difference. And you cite a couple of examples of that. Do you want to share them?

SHAH: Right so pretty early on in the cholera pandemics of the 19th century, there was doctors who realized that, you know, if we administer fluids to these patients they seem to get better. And there was actually a study that was done at a prison in England. There's a bunch of prisoners who had a cholera outbreak, and they were given fluids to replenish their - you know, the dehydration of cholera. And the death rate plummeted. And so this doctor then called all the, you know, famous sort of medical establishment elites to come see his results. And they came and they looked around in this prison and all of the prisoners were well. You know, they weren't dying of cholera. They actually had recovered, and they said well, obviously there was no cholera here because if there was cholera, you know, all these people would be wasting away. So therefore, whatever you treated must've been something different. So they really just dismissed it out of hand. And it was partially also because the doctors who were saying this were not part of the - you know, the elite - the London medical elites. They were kind of younger doctors or doctors from kind of the outlying or the colonies and things like that. So their evidence was really discounted and ultimately mocked. They said oh, well, we can't - you know, we can't give salty fluids to our patients. You know, that's what we do to, you know, pigs and herrings.

DAVIES: And there were also some who actually drew an empirical connection between contaminated water and the spread of cholera. They were also mocked, right?

SHAH: Yeah. And that had happened, you know, right from the beginning, too. People started noticing this connection. And then of course, we had John Snow the famous anesthetist who, you know, mapped an outbreak in Soho, London, and showed very clearly that it was a contaminated pump that was distributing this water to people. And he understood that miasmas didn't make sense because he was an anesthetist, so he was a specialist in gases. And he knew that if you inhale a poison it would affect your respiratory system. And he saw clearly - everyone knew that cholera patients - you know, their respiratory systems were not affected. It was their G.I. system, you know, their stomach, the gut. So he understood that it can't be something you inhale. It must be something you swallow. And he showed that really clearly with his famous map of the Broad Street pump in Soho, London, which, you know, showed this cluster of cholera cases happening around this contaminated well. But the medical elites of the time, you know, they gathered together. They held a meeting and they reviewed his findings. And they said well, you know, maybe cholera can be carried in water, but it's also carried in air. And of those two factors, air is by far more important. And so John Snow's finding that contaminated water was carrying cholera was really not believed for several decades later.

DAVIES: You know, what's interesting about this was the - when you get into a frame of mind, you miss important clues, you miss evidence. And you note that while modern science is obviously far more sophisticated and empirical that there are ways in which our own approach to pathogens probably limits the way we treat them. You want to talk about that a bit?

SHAH: Well, that report that leaders of the medical establishment in London issued about John Snow's finding when they said oh, well, maybe it's water. That's true, but that's not important. Really air's the most important thing. It just - it really struck me as so similar to what we do today with, you know, social and political factors in disease outbreaks where we really look at the biomedical causes of diseases. And we focus on that as if that - you know, we'll kind of reduce diseases to the what are the kind of smallest factors that cause them - the microbe, the insect - and then we surgically attack those with chemicals. And that's sort of the biomedical, you know, model, and it works for a lot of things. You know, it's worked really well for a lot of things. But what we're seeing today is a lot of these new pathogens are being driven into human populations through social and political factors. And yet our general response to that is to say well, yes, yes, there are social and political factors. But really it's - you know, it's the biomedical factors that are most important. It's really - it's about the germ that we need to attack, you know, with surgical precision. So it really echoes what happened with John Snow to me.

DAVIES: Sonia Shah's new book is "Pandemic." After a break, she'll talk about our warning systems for detecting of new infections, and I'll ask her what keeps virologists up at night. I'm Dave Davies, and this is FRESH AIR.

(SOUNDBITE OF MUSIC)

DAVIES: I'm Dave Davies, in for Terry Gross who's off this week. We're speaking with science writer Sonia Shah, whose new book looks at the growth of infectious diseases which are spreading with increasing frequency across international borders, from Ebola to swine flu to the Zika virus. Her book is "Pandemic: Tracking Contagions, From Cholera To Ebola And Beyond."

How effective are our warning systems for discovering new pathogens? I mean, there are protocols in, certainly, industrial countries and there's a World Health Organization. How quickly do we get onto pathogens and respond to them?

SHAH: Well, it's interesting, I think a lot of times when we talk about, you know, being more prepared and preventing pathogens from spreading or preventing pandemics, what we're really talking about is, you know, first response - like, you know, stepping up our first response so that when we have outbreaks of disease that our hospitals are prepared and we have the vaccine stockpile and we are able to fly our experts around really quickly to get to the scene of the outbreak and things like that. But that's not actually preventing these pathogens from emerging and from causing outbreaks, that's kind of - you know, after the fire has started then we rush in with our fire extinguishers. But to really prevent them would mean stepping it way farther back, and that is possible now because we - you know, we don't know which pathogen will cause the next global outbreak but we do know how it happens and where it's more likely to happen. So we know that there's certain places that are - you know, have higher risk of pathogens emerging and we can do kind of active surveillance in those places by, you know, mapping the microbes that are there, by surveilling people or animals who are more likely to, you know, spread or to have spillovers of microbes into their bodies. And we have, you know, more advanced detection capacity now with, you know, genetic analysis and other kinds of ways that we can see where these invisible microbes are spreading and changing.

DAVIES: So what's an example of an area that might be, you know, ripe for the development of a harmful pathogen? What's a hotspot?

SHAH: So we know, for example, in South China, there's a very particular ecology there where we have a lot of wild waterfowl which are the reservoirs of avian influenzas, and we have a growing chicken industry, poultry industry, where a lot of these poultry are - captive chickens are being kept in giant factory farms. And we know that this leads to the emergence of novel forms of avian influenza. When influenza from those wild ducks falls into these chicken farms, they - those viruses replicate really rapidly. They evolve and they often become more virulent, and some of them have even evolved in ways that can infect humans. So this is sort of an ongoing risk, right, and so we know this. We know that's how it happens, and so we can do active surveillance. We can look at those birds, we can analyze their scat, we can surveil the workers who, you know, handle the birds most closely to see - where are these viruses coming up? Are they spreading? Are they changing? And if so how? And there are organizations that are starting to do that.

DAVIES: Let's talk about the Zika virus. It's appeared, I think, in 30 countries at this point and, you know, may be linked to microcephaly, you know, which has produced smaller heads in some children. As you look at this, what questions has this episode raised for you? Or, what observations would you share about the epidemic and the public health response?

SHAH: Well, I think Zika is just a great example of how new pathogens are emerging today. It came out of the bodies of animals. You know, for many years, we had Zika virus in the equatorial forests of Africa and Asia. It mostly affected monkeys and possibly other creatures too, but it very rarely came into humans. And that's typical of a lot of the new pathogens we're seeing today, they live in animals. And then we don't know what the triggering event was that allowed Zika virus to start spreading into humans, but we do know what it exploited, and it exploited two things that are - you know, a lot of other pathogens have exploited too, which is urbanization and flight - you know, flight travel. So in the 1940s and '50s and '60s when we had Zika virus in, you know, in the forests of Africa, it was carried by a forest mosquito and that mosquito very rarely bit humans, it mostly bit animals, which is why we didn't have a lot of Zika virus in people - at least, that's one reason why. What we're seeing now is Zika virus has crossed over into a mosquito called the Aedes aegypti, and this is a mosquito that has expanded its range over recent years as we have urbanized. It is - it specializes in living in human cities. It loves garbage. It can, you know, breed in sort of a drop of water in a bottle cap. So all of our plastic garbage, our metal garbage, provides breeding sites for this mosquito and it only bites humans. So once we had Zika virus coming into Aedes aegypti, this highly urbanized mosquito, you know, that's when we started having this explosive spread. And, of course, it traveled from Asia. You know, it came out of Africa, it came into Malaysia and then into - probably into the Philippines, Micronesia and French Polynesia, and that was sort of this slow spread. But then the rapid thing happened - the expansion happened when it came from French Polynesia into Brazil. And that was almost certainly through a flight, either people from French Polynesia coming to Brazil for the World Cup or possibly an international canoe race, but whatever it was, it was on a flight that it came over. And then from there it's able to access these huge, highly urbanized populations that have no immunity, and that's what creates the epidemic.

DAVIES: Are officials doing what they should be doing?

SHAH: I think - you know, I think the problem with these - with our response, our after-the-fact response, is exponential growth of these pathogens has already started, right? So one person's infected, that person infects five more, each of those infect five more, et cetera, et cetera, et cetera. So by the time we are starting to try to corral this thing, you know, our response is linear at best. Meanwhile, we're fighting a disease that spreads exponentially. So there's always a mismatch. I think we're doing everything we can right now. Is it going to be enough to stop the spread of this virus? I don't think so.

DAVIES: You write about that corruption was a problem, and not just in the developing world, but that a lot of commercial interests in the 18th and 19th centuries helped cholera spread, for example, by effecting decisions about public water supplies and sanitation. What's the record in the 20th century? I mean, how many nations, for example, suppress news of outbreaks or, you know, serve specific business interests in ways that undermine our ability to fight these pathogens?

SHAH: I mean, unfortunately this still happens. We're getting better at it, but, you know, there's been suppression of news about new disease outbreaks again and again in - you know, just in recent years. So, you know, cholera came into Cuba, and Cuba was suppressing news of that. When SARS emerged in China, China attempted to suppress news of that in the beginning. New antibiotic-resistant pathogens that have come up in India - you know, the Indian government has tried to sort of shush that up or minimize the threat. So this happens still to this day, but I think, you know, in an even kind of bigger way, we know about the risks that certain industrial practices have in creating these pathogens that are, you know, killing more and more people. And a good example of that is antibiotic-resistant pathogens in this country where, you know, we've known since antibiotics was first developed that if we use them in ways that were not medically necessary that it would lead to the evolution of resistant path - resistant bacteria. And yet in this country, 80 percent of our antibiotic consumption is not medically necessary, it's done for commercial reasons. You know, when we have livestock farmers giving antibiotics in low doses to their animals because it fattens them, you know, it helps them gain weight faster and that's - you know, makes - gets them to market faster. So this is a commercial use. And that's - the vast majority of the antibiotics that are consumed in this country are for that reason. And we've known this, you know? We've known this for years. And we do have an increasing problem with antibiotic-resistant pathogens, which is a very serious problem where we're running out of these drugs to treat these runaway infections and, you know, we're soon - we're on the cusp of entering an era when we have no more antibiotics that work for some of these bugs, and yet it's been very difficult for our government to control this practice. You know, we've made sort of, you know, very, very small baby steps but only in recent years.

DAVIES: This is pretty scary stuff, and, as you have spoken to epidemiologists, I mean, how likely do they think it is that we're going to see a pandemic in coming years that could kill, you know, tens of millions of people?

SHAH: Well, a recent survey was - a quite alarming recent survey found that the majority of epidemiologists that they talked to - actually, it was pandemic experts of all kinds - felt that a pandemic that would sicken a billion people, kill 165 million people and cost the global economy about $3 trillion would occur sometime in the next two generations. So, you know, I think this community of experts is definitely bracing themselves for what's been called the next big one.

DAVIES: We're speaking with Sonia Shah, her new book is called "Pandemic." We'll continue our conversation in a moment. This is FRESH AIR.

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DAVIES: This is FRESH AIR. And if you're just joining us, our guest is science writer Sonia Shah. Her new book is "Pandemic: Tracking Contagions, From Cholera To Ebola And Beyond." You know, you've had some encounters with pathogens in your own family. How much do you think about it? How have you changed the way you live?

SHAH: You know, the way I think about it is we live in a microbial world. You know, we have microbes in our bodies. Most of them help us. We have microbes in our environment. Most of them ignore us. There's a few pathogens around, but that's microbes sort of doing their thing, right? They find a niche, they replicate, they take over as much as possible, go right up to the limit because that's what microbes do. And so that's the world we live in. So our relationship to disease and pandemics is really - it's part of our relationship to the natural world. It's a risk that we have to live with. So yeah, I do things like - you know, I keep up with my vaccines and I wash my hands and, you know, I avoid sort of factory meats and things like that. But in the end, this is the world we live in. We have to live with this risk, and all we can do is minimize it. And I think there's lots of ways we can minimize the risk of these new pandemic-causing pathogens from emerging.

DAVIES: On a policy level you mean?

SHAH: Absolutely. I mean, I think there's - you know, there's ways to (unintelligible) for them better. There's ways to - you know, we kind of went through this whole thing with environmental damage, right, where, you know, we would, you know, develop minds and industrial facilities and such. And then later we would say oh, whoops, well, that's kind of contaminated all the water or that kind of, you know, ruined this forest where this endangered species is now remaining. But we don't do that with pathogens. We kind of wait until they become a problem and then we start dealing with it. And I think what we could do is, you know, mitigate the risks before they start to manifest themselves. We can insure against the risk in some capable. For example, air travel - we know this is risky for spreading pathogens around. Does it mean we have to stop flying around? Well, maybe not - maybe we just insure against it. You know, maybe we put a 1 percent tax on, you know, international flights to pay for surveillance for new pandemic pathogens. Or maybe we say OK, maybe we shouldn't develop into this - you know, to build a mine in this sort of pristine remote wildlife area because there's a lot of animals there that have microbes that could spill over into our bodies and we'd be vulnerable that. You know, we don't really evaluate these risks in advance. We wait until they become problems. And I think we could switch and we could be a lot more proactive.

DAVIES: Should pharmaceutical companies or the government focus more on creating new antibiotics to fight these strains?

SHAH: There's two parts of it. We need to use antibiotics more rationally. We don't do that now. That's sort of the hardest part of it that we need to do. But the other part of it is we also need to develop new antibiotics to keep up with the - you know, these pathogens are always going to evolve resistance eventually. So we always need to come up with new, you know, weapons to fight them. And the problem with antibiotics is that we've gotten used to spending very little money on them. You know, the average consumer - we don't want to spend more than, like, 50 bucks on an antibiotic even though it saves your life. And for drug companies, you know, it's a bad market because antibiotics, they don't get used every day. You know, better to create a drug that - you know, somebody has to take an anti-cholesterol drug one a day for the rest of their lives then a course of antibiotics that's over in a week, right? So for all these reasons, our market incentives don't really work for producing these drugs that we actually really need. And so the whole way our medical development model runs, which is, you know, based on what drugs can sell the best. Those are the drugs that we develop, and that's not necessarily going to meet our - you know, what we need for public health.

DAVIES: Is there a particular kind of pathogen that keeps, you know, epidemiologists up at night?

SHAH: I think there's two. I think novel forms of influenza is what really keeps most virologists up at night because we are so good at spreading those around quickly, and it happens every year. You know, we have a flu pandemic every year, and now we're hatching all kinds of - new kinds of flu viruses, you know, mostly in Asia and then they're spreading across the globe. And we don't have immunity to some of those. And that means that even - you know, right now, a typical flu virus - the seasonal flu will still kill a lot of people every year. And it's a real drain on our global economy. But we kind of put up with that. So if you had a new flu virus that even had a slightly higher mortality rate, you could see a lot more death and destruction because really, every - so many people get the flu. I mean, you think about the 1918 flu which killed, you know, maybe 100 million people, maybe more. Estimates vary but certainly huge numbers of people died from that flu. The morality put rate was, like, 1 percent, which isn't huge. You know, it sounds like a kind of small number. But when you think about how many people get the flu, that adds up to, like, a huge number of deaths. So these new kinds of influenza I think are what virologists are most fearful of. But then the other one is the antibiotic-resistant pathogens because the idea that we could have infectious bacteria that we have nothing to use against - you know, and one by one that's happening. They're getting closer and closer. Each class of antibiotics has been rendered useless by some new antibiotic-resistant pathogen. And that's - you know, that progress keeps going farther and farther until people can really foresee a time when, for example, you wouldn't do surgeries anymore, right, because you wouldn't do a lot of things that would risk getting any kind of infection because it might be an untreatable one. So we'll say your - you know, your knee replacement surgery or, you know, some other elective surgery that's not life or death you might - I think most doctors would say at that point when we have - you know, when we've truly entered the era of untreatable infections that it's not worth it anymore. So it'd really change the face of medicine.

DAVIES: It's almost like letting go of this notion that we had, which is that industrial society had put this era of pandemics behind us. It hasn't.

SHAH: That's right. I think, you know, many of us who, you know, grew up in the '80s and '90s - like, you know, I was born in 1969 - and antibiotics still worked then and, you know, doctors had an answer for everything. You know, and then we had HIV in 1983, and then we had, you know, these antibiotic-resistant pathogens. And, like, sort of one by one, it seemed like wait a second - like, that whole era, you know, a generation - I mean, we had the first antibiotics in 1940s. And then by 1980s, it - you know, we started having these pathogens that can't be tamed by medicine easily. So it would really - if you look in the kind of larger picture, that period was the aberration - that period when we felt like we were on top of the pathogens and that we had tamed the microbes, that was the anomaly. And what is really, you know, the sort of underlying condition is that we are at their mercy and we have to manage that risk.

DAVIES: Sonia Shah, thanks so much for speaking with us.

SHAH: Thank you.

DAVIES: Sonia Shah is a science writer. Her new book is "Pandemic: Tracking Contagions, From Cholera To Ebola And Beyond." Coming up, Maureen Corrigan reviews Ethan Canin's new book "A Doubter's Almanac." This is FRESH AIR. Transcript provided by NPR, Copyright NPR.