President Trump likes to call the coronavirus the ‘Chinese virus’, thereby popularizing the picture of the pandemic as a foreign invasion. He is not alone.
While we (hopefully) don’t use a racist term to refer to this virus, many of us unwittingly bought some paradigm to understand pandemics. Call it the invasion paradigm: the idea that we are being attacked by an attack from foreign animal pathogens, and we are only passive victims.
But what if we, the people, are the ones organizing the attack? What if the real story of modern pandemics isn’t about how animals and their germs invade our human realm, but how we invade theirs?
That’s the argument of Sonia Shah, author of the 2017 book Pandemic. She says the paradigm of invasion – or “microbial xenophobia,” as she calls it – often doesn’t explain why a microbe that has been around for centuries suddenly turns into a pandemic-causing pathogen. After studying outbreaks ranging from cholera to West Nile virus and Ebola, she discovered that human activities play a huge and hugely recognized role.
Our environmental and social policies – such as clearing forests or failing to address a housing crisis – make it much more likely that a previously harmless microbe will cause a devastating outbreak.
Shah is not alone in advocating a paradigm shift in how we understand pandemics. The A health movement, an interdisciplinary mindset endorsed by a number of global public health authorities, emphasizes the connections between people, animals, plants and their shared environment. It also calls for this change.
I spoke to Shah about how this approach can help us better understand the true origins of pandemics. A copy of our conversation, edited for length and clarity, will follow.
The main story in many people’s minds is that ‘exotic’ animals are to blame for the coronavirus crisis – that they are dirty and infected with tons of pathogens that just can’t wait to kill us. What is wrong with this story?
First of all, we all have a lot of microbes in us. Humans give animals microbes that turn into pathogens all the time, so we are also the source of diseases for other species. But we are not talking about that.
Species are full of microbes everywhere, but if they remain in the bodies in which they evolved, they don’t cause disease. Ebola does not cause disease in bats. Neither does Coronavirus. They cause illness in our bodies because they are new to us – they exploit a new habitat.
So why are they exploiting that new habitat, which is us humans?
It is because we build roads between wild animals and human bodies. We use a lot of land – for our cities, our mines, our farms – thereby destroying the habitat of wild animals. That’s why 150 species go out every day. And the species that remain must squeeze into these tiny fragments of the wildlife habitat that we leave for them.
If you cut down the forest where bats live, they don’t just go away; they settle in the trees in your backyard or farm. That means it’s easier to have casual contact with their feces.
If a small child goes out and plays near a tree where bats sleep, they might pick up a piece of fruit with some bat poo or saliva on it and stick it in their mouth, and you’ve created an opportunity for the microbes that live in the bat body to enter a human body. We know there was one spill event at Ebola – the first case was a 2-year-old child in West Africa playing near a tree where bats live.
These are accidents that have yet to happen. Now we have this great flight network, so even if pathogens show up in a place where there aren’t many transmission options, they can easily get where they are. We also urbanize ad hoc, so we have many places where people are exposed to each other’s waste. There is not much infrastructure in many places that are urbanizing quickly. All of these factors combine to increase the risk of a microbe entering human bodies and then spreading.
What strikes me is that when you talk about the origins of pandemics, you talk at this macro level – like our environmental and social policies – rather than at the micro level. In terms of explaining the origins of previous outbreaks, what kind of explanatory power does this approach give you?
We often see an outbreak as a foreign problem – such as Ebola and SARS and Zika come in from outside and invade us. That is the traditional story: the germ that penetrates from the outside. I call it microbial xenophobia.
But these are things that are happening here in the United States. For example, the West Nile virus is a virus of migratory birds from Africa. They’ve been landing in North America for hundreds of years, but we never had the West Nile virus here until 1999. Why is that?
It turns out that when you have a variety of bird species in your home flock, you don’t get much West Nile virus, because birds like woodpeckers and rails are really bad carriers. So as long as you have a lot of those different bird species around, even if you’ve introduced a migratory bird’s West Nile virus, you generally don’t get much virus.
But what has happened in the past twenty years is that we have lost much of that bird biodiversity. Woodpeckers and rails became rare in many environments. Instead, we have many birds like crows and robins, generalist species that can live in any affected environment, and they are really good carriers of the West Nile virus.
So the less woodpeckers and rails you have, and the more robins and crows you have, the more West Nile virus you have. And the more likely it becomes that a mosquito will bite an infected bird and then bite a human.
Since tick-borne diseases are a huge problem in the U.S., I’m curious: Is there a similar story to tell about Lyme disease?
Yes, it is a similar story to Lyme. When we had intact forests across the Northeast, we had a variety of forest type species that lived in those intact forests – such as opossums and squirrels – that helped control the tick population. But in the past 50 years, suburbs have grown into the forest and broken up into small patchwork, so opossums and squirrels have become [relatively] special.
Instead, we have a lot of white-footed mice and deer, and it turns out that white-footed mice don’t properly control the tick populations. A typical mouse destroys about 50 ticks per week, compared to a typical possum that destroys hundreds and hundreds of ticks per week by grooming alone.
So the fewer opossums you have and the more white-footed mice you have, the more ticks you have. And the more likely you are to get outbreaks of tick-borne diseases like Lyme.
I think that it really helps that our interaction with the environment – for example deforestation – has major implications for human health. Social policy can also affect the risk of an outbreak, right?
Okay, so when dengue broke out in South Florida in 2009, it was immediately considered an invasion from a strange place. We covered the environment with insecticide and conducted a military attack on these mosquitoes. But it turns out that the mosquitoes with dengue have been in South Florida for a long time. That was not new.
What was new was the execution crisis. It had closed all these houses. The epicenter of the dengue crisis was also the epicenter of the mortgage crisis.
And of course, people in South Florida have many pools. So with all these houses closed, these pools were empty. See, it starts to rain and these empty pools fill with water and it creates these little bags around the garden where mosquitoes can reproduce. And then we have this “unprecedented” outbreak of dengue.
No one thought of addressing the housing crisis as a possible cause of the outbreak.
It sounds like you are in favor of a more holistic approach, a systems thinking approach. To what extent are you there?
There is a whole movement in global health called A health. It is the idea that human health is related to the health of our animals – pets, livestock, wildlife – and our ecosystems and other societies. All of these things are interrelated and we need to look at these wider drivers as that will address the core of the problem. Otherwise, we are constantly cleaning up problems that erupt over and over.
I notice that this also has consequences for how we practice science. Given that so many of our modern pathogens cross disciplinary boundaries, do we need more doctors working with vets, more biomedical experts working with social scientists, and so on?
Absolutely. We’ve silenced everyone and you can see how it affected the way we responded to some of the zoonotic pathogens. With the West Nile Virus, vets at the Bronx Zoo commented, “Oh, all these birds are getting sick of something.” But they didn’t tell the doctors, so the doctors just said, “Oh, all these people are getting sick of something! What’s going on?”
We’ve blinded ourselves to the crossovers by making sure these groups don’t talk to each other. Part of the One Health idea is that we must be multidisciplinary and bring all these experts together.
The fact that the coronavirus probably comes from a wildlife market in China makes me wonder about factory farms in countries like the US. It is not the same, but animals on these farms are also very close together. Should the coronavirus crisis prompt us to revise our thinking on meat production here too?
That is absolutely part of it. When I was writing my book, I asked my sources what kept them awake at night. They usually had two answers: highly resistant forms of bacterial pathogens and virulent avian influenza. Both of these things are driven by the crowds on factory farms.
These are ticking time bombs, and they will still be there when we have finished cleaning up the mess we have acquired with this current virus.
In your book, you write about paradigm shifts, and a line that struck me was, “The fundamental approach of modern biomedicines to solve complex problems is to reduce them to their smallest and simplest components.” Do you think this reductionist approach is failing us now?
The reductionist approach in biomedical medicine comes from a good place. Modern germ theory has really made a big difference. Before we had germ theory, people thought that cholera, malaria and so on were caused by airborne miasms or by an imbalance of humors in your body. Germ theory has helped us in many ways, so it makes sense that that’s the paradigm.
But we have lost the bigger picture, the connections between social and political health and environmental health. So what we see now is an intense amount of reductionism.
Looking ahead, we need to see that pandemics, climate disasters, are all related to our huge footprint on the planet. We have used a lot of natural resources and now the bill is about to expire. We are going from disaster to disaster until we really start to change the fundamental relationship between us and nature.
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