Special Episode: Carl Zimmer & Airborne

rest of this season. If you would like to see the full list of books that we've covered so far, as well as get a sneak peek of the books that will be featured later this season, head over to our website This Podcast will Kill You dot com, where you'll find a link to our bookshop dot Org affiliate account. Under the extra tab, there you'll see several TPWKY lists, including a book club list. Check back on that list regularly,

as I'll be updating it throughout the season. As always, we love getting your feedback, whether that's a topic request, a suggestion for a book to feature in one of these episodes, or just any other thoughts you have. You can reach out to us via the contact dose form on our website. Two last pieces of business before we get into the meat of the episode Number one, Please rate, review, subscribe. You've heard us say a million times, but it really

does help us out. And number two, did you know that we are now posting full videos of many of our newest episodes on YouTube. Make sure you're subscribed to exactly Write Media's YouTube channel so you don't miss an episode. By now, we are all fairly familiar with the concept of the microbiome, the community of microbes that live in a particular environment, such as your gut, or your skin, or maybe even inside your belly button. But how many

of you have heard of the aerobiome. We don't often think of the air as a medium teeming with microbial life, but as Carl Zimmer demonstrates in his latest book Airborne, The Hidden History of the life We breathe, that may be a critical oversight. In this book Club episode, award winning science writer Carl Zimmer joins me to discuss the long neglected science of aerial life and the public health

implications of this research. Many of you may recall the debate that sprung up seemingly out of nowhere in the first couple of years of the COVID pandemic, when scientists couldn't seem to agree on whether the virus was transmitted via respiratory droplets or whether it was airborne. Why this distinction mattered and how the issue grew so contentious is

just part of what Zimmer covers in Airborne. By placing this debate in the broader context of the history of aerial biology, he draws a line from the early days of germ theory to the pioneers of this emerging field, from the height of biowarfare research to a Washington State choir in the first weeks of the COVID pandemic. Linking together these disparate stories from the history of science, Zimmer presents a revelatory picture of a scientific field you didn't

know existed. How might the COVID pandemic have been different if we acknowledged the airborne potential of this virus earlier? What lessons can we draw from this oversight to apply to future outbreaks? What even lives in the air, and why does it matter? We get into all of these

questions and so many more. According to a quick Google search, we breathe about twenty two thousand breaths a day, breaths that we don't often think about, but after this episode, you'll have a newfound respect for those breaths and the invisible airborne life all around us.

COVID pandemic. I was working at the New York Times, and I, along with my colleagues, we were just trying to write as fast as we could about this totally new disease. And you know, it was challenging because scientists themselves are trying to figure out what exactly this disease is like. And one of the biggest sumbling points, one of the areas with the most debate and uncertainty, was how it spreads. You had people telling you on TV

to wipe down your groceries. I know I did, and just you know, keep your distance from people, and you know, you'll be fine. Then there were other there were scientists, a small number of scientists at first, who were saying, we think this might be airborne. World Heart Organization explicitly saying COVID is not airborne, and you know, it took a couple of years, and then world health organizations that yeah, it's airborne. And I just thought, why was that so hardy?

And the scientists themselves said to me, like, well, you need to understand the history. One scientist said, you know, history set us up. And so that led me down this path to discover this whole history of this science of the life in the air, which is called aerobiology.

I mean, it's not unusual to see an insect in the air, but scientists have long suspected that that maybe large numbers of insects flying long distances high in the air, thousands of feet in the air. The problem is you can't see them, and so scientists have invented technology st barring radar and tuning it so that you can detect insects that are in large numbers that are way up in the air. Lo and behold, there are a lot

of insects up there. And just to give you one example, and there's a study that came out last year and from China where just in a small region of China, they set up some radar systems to look up and over the course of a year they recorded nine point four trillion insects just in that place.

the air. I mean they have adapted beautiful like little cannons and other devices to get their spores up high enough so that the air can carry them away and then they can go all the way up to the stratosphere. Fungi loan they lift up about a trillion trillion spores every year.

a few seconds. But it is possible for them to go up and then keep going up, and then eventually they get so high that they're just riding along long distance waves and they can actually go thousands of miles, so they can be floating for days. You know eventually they will land. I mean, it's just a matter of time. But because there's so many things coming up all the time, it's always a very lively space. So like the clouds,

for example, every cloud you look at is alive. It's it's got you know, trillions of bacteria something something on the order of that. And you know the bacteria, there are signs that they might be growing in the clouds, and that means that they are eating the clouds. So you know, it's a different way to look at the sky and think about what's up there.

the biggest infectious disease killer by far is tuberculosis. It's caused by bacteria, and those bacteria are totally airborne. In other words, they really can't infect people in any other way other than people releasing little droplets that float out, not just you know, maybe when they cough or sneeze, but even when they're just breathing, they are going to release droplets, some of which have tuberculosis bacteria in them. These are so good at being airborne that they actually

manipulate us. They actually have adaptations to sort of essentially tickle our airway to get us to cough more, because that gets them out and gets them into the air, propels them and then they can float off and infect someone else, and they make the droplets make their way into the very finest tips of our airway endings. In the lungs, the lvoli and that's where the bacteria can grow. So tuberculosis kills over a million people a year. But you know, it's also a huge threat to in terms

of pathogens. It's also a huge threat to our crops. So there are lots of disease is, particularly fungi that spread through the air in part or entirely. I write a lot about a kind of fungus called rust, which can just you know, it can endanger the food supply of whole countries if it really breaks out seriously. So I'm just giving you two examples, but there's a long list. And you know, is there something about airborne pathogens that

you know they all have in common? I would say they're rugged in the sense that they can survive being floating around in the air. It's not easy to be a pathogen floating around out in the air. It's hard. And there's some viruses that don't last very long when

they're exposed air. Other viruses can last a really long time, and it might be that they sort of they have adaptations that let them kind of use the chemicals inside of those droplets that come out of our lungs to sort of shield themselves from the elements.

going on for quite some time. And before we get into how that controversy started in the germ theory myasthma debate, what role did people think the air played in diseases before germ theory.

here in Connecticut, it's a beautiful sunny day. The air feels very lovely, but you know there are also days where you like, it smells really wrong, or there's a there's a weird light in the sky because there are wildfires someplace, and you know, like the the air is unpredictable. And so Greeks had this idea that gods could visit

curses on them and they would call these miasthmas. And Hippocrates said sort of took that name and applied it to what do you call it, like corruptions of the air, so that if you breathed in that air, you would become sick. And there were different miasthmas for different diseases, and even different species could get different diseases because they had their own miasthmas, but they were all transformations of

the air itself. It had a certain explanatory power. I mean, how was it that, you know, a bunch of people in this same town all would get the same disease around the same time. You can imagine, well, you know, a breeze just came through and people all inhaled it and then they all keeled over. But that explained plague, and you know influenza, and you know malaria literally like

bad air, like that's what the disease name means. And so it held on for a long long time until people who had been discovering and studying microbes said no, wait, we think these are responsible for these diseases. And it was a very you know, it was a very long slog I mean to us in hindsight, it seems obvious, but you know, this was a battle that started around seventeen hundred and lasted up until about nineteen hundred, so about two hundred years of a long drawn out fight.

to believe. I love that line. But he would go outside with flasks and he would catch bacteria. They would fall down the long neck of the flask and fall into sterile broth and start multiplying. And he did it in Paris streets, he did it in farmland around France, and the even climbed a glacier, which was my favorite

episode of this. And he actually initially said that he thought that lots of diseases were caused by these floating germs, by airborne germs, but it didn't really go that way, and what happened instead was that as as scientists definitely showed that the diseases were caused by germs. So, for example,

cholera not caused by miasma as the authority is claimed. Instead, it was caused by Fibrio cholerae, like one particular bacteria, and that particular bacteria spread in water, so you have a water borne disease and then you have other bacteria that get into food and contaminate food, so you have food borne diseases. You have you know, bacteria that spread through sex, sexually transmitted diseases, and on and on and on. So it was like the germ theory disease was taking

one disease after another out of the air. Yeah, and by the early nineteen hundreds you had very prominent public health figures saying we don't need to worry about the air anymore, like this should be a relief. The air has been this specter of infection since Hippocrates. They literally said this, and now you don't need to worry that. I think that really did keep people from really thinking

very much about life in the air. And they also didn't have very good technology for really measuring and capturing life in the air. So that combination really did lead to a real, very strong consensus starting in the early nineteen hundreds that has endured for over a century.

a plant pathologist. He worked at the US Department of Agriculture ever since he was like twenty years old, was just his lifelong employer, and he was part of this tradition of studying diseases that affected crop like watermelon and wheat and so on. And they were very comfortable with the idea of airborne disease because there are these spectacular crop failures, like you know, the the Great Irish Famine that was caused by potato blight that in part was

airborne that organism. So by the early nineteen hundreds, plant pathologists. They knew that things moved through the air, they just didn't know how far they could go or high they could go. And so eventually fred Meyer says, like, I am going to try to figure out how high and far I can go to catch them. And this was something that his bosses did not want him to do, so he just did it on the side on his

off hours, and it's kind of spectacular. He would he would jump into planes, these open cockpit cockpit biplanes, and you know, he'd have these petra dishes stuck on to handle wooden handles, and he would just basically be waving his arms around out of a flying plane in the clouds, and the pilots would just be totally baffled by him. But he'd bring these prejudicies back to his lab and

he would grow stuff. He was catching things. So then he started looking for opportunities to send more sophisticated devices higher and farther. So, for example, Charles and n. Lindberg, they flew in ninety thirty four across the North Atlantic over Greenland, and he talked them into trying to catch

life as well, and they did. And then there were these explorers who got into sort of metal spheres that were attached to giant balloons, and they went up to the stratosphere, and so they took along with them probes that Meyer had to see if life could survive up in the stratosphere. And then on a second voyage, they actually were able to catch stuff up there in the stratosphere.

Real kind of unbelievable to me is that by nineteen thirty seven Meyer had done assembled so much dazzling work that he was able to talk the government into creating a whole new service in the government, a kind of centralized lab for life in the air, and he was going to head it. He coined the word for the

science that they were going to do, aerobiology. He came up with that word in nineteen thirty seven with this plan, and everything was looking great, and then he went on his you know, sort of made voyage across the Pacific in search of search of life and was never heard from again. So I feel sometimes writing about these people, there's there's a certain curse that hangs over aerobiology.

gain hold. There was more interest in aerobiology and the potential of air as a way to transmit disease and how to protect ourselves from that. And I think it's interesting to think about these two sort of lenses through

which people viewed aerobiology. You have Fred Meyer on the one hand, who's just interested in the rich tapestry of life in the air, and then you have more of the US government interest at the time, in part shaped by global politics, where it's like what about bioweapons, what about biodefense, And how did that branch kind of grow more or gain more interest than Meyer's side.

to reach out to these aerobiologists. They would say, well, what do you think, what do you think are the what do you think are the risks that we face? And so there was one aerobiologist named Ellen Stackman who wrote a very long memo based a lot on the work that he and Fred Meyer and others had been doing, saying, yes, we could be attacked, and here's what could happen. So

I mentioned stem rust. So he said, you could imagine someone dropping a stem rust bomb over our farms and wiping out our food supply, and you know, they someone like Stackman, who had, you know, been involved in World War One, could see like what happens when an army loses a food supply. Because Germany actually had its own potato light, you know, this airborne disease that was devastating to its food supply and that may have really tipped the balance of the war. So he said, we need

to be aware of that. We need to have like plant pathologists looking out for attack and so on. But then it's quite amazing, like in writing, is like, we have to explore developing our own weapons. It would be remiss of us not to. It would be irresponsible for us not to start building our own arsenal. You know. It's kind of like the nuclear sort of logic, like, well, if they're going to be building him, well we should too as defense. And he had this He said, here's

how you could like go after Japan. You know they have these rubber plantations for their tires for their vehicles. Well, here's a MicroB you could drop on their rubber plantations and wipe those out. He really thought a lot about this. And there were other aerobiologists, William and Mildred Wells, a husband and wife team who in the nineteen thirties had been showing how people can spread diseases to each other

through the air. And William Wells in particular had developed all sorts of really elegant devices to demonstrate how germs can float in the air and also then to sort of measure how much you would need an animal to inhale to die. The military, you know, at Camp Dietrich, they started building very similar devices they took secretly without his awareness, They secretly started building these devices so to figure out, well, how instead of saying, like, well, how

do we understand these airborne diseases to protect people? How do we build better weapons? Like what's the minimum dose we need of anthrax in the air to kill these mice? And they did all this resent in a giant building literally called the Aerobiology Building, and you know, the United States, the Soviet Union and other countries you know, would go on for decades to build huge stocks of biological weapons, all firmly based on this new science of air biology.

and then he gets pulled into World War One. His job is to clean the water for the soldiers, and so he is protecting, you know, American soldiers by providing clean water. But meanwhile they're dying of influenza, not a waterborne disease, and it's not really clear how it's spreading, but I think that the seeds were planted there that they thought maybe this is airborne, despite that prevailing view that diseases are not airborne. So he comes back from

the war. He's married Mildred Wells. She had gotten a medical degree, but she didn't practice medicine. She was raising their son who probably had some sort of psychiatric disorders. Just judging from medical files, I was able to come across later. They have a good run. In the twenties, he continues studying oysters. He gets famous for being the oyster Godfather because he's figuring out how to breed oysters. And then the Great Depression comes and he's out of

a job. Mildred somehow gets a job studying the epidemiology of polio, and she actually contributes to a book about it, and she develops this idea that maybe polio is being spread through the air. She doesn't really develop it a lot in her writings, but it definitely influenced William Wells.

He gets a job at Harvard teaching. He's terrible at it, like just I mean, I'm not making it up, Like the dean of the school, bubble Galth says, this is something that Wells does very badly, Like it's in writing, and he in particular had a very difficult time with communication and just he would get into arguments with people or long long monologues. Mildred was really fierce herself. They didn't make friends, and put it this way, They're brilliant,

but they alienated everybody. But at Harvard they start to do some experiments that actually established some of the basic ideas about airborne infection. In other words, that you know, when you breathe, you are releasing droplets and some of them have can have viruses or bacteria in them. They can float around for hours, maybe days in the right conditions, primarily in indoor spaces, and they even show that you can use ultraviolet light to kill them in the air.

First they do this with, you know, with experiments on animals. But then when they moved to Philadelphia, they put ultraviolet lamps in a school and in nineteen forty there's an outbreak of a disease we's been hearing a lot about recently, measles. At the time, there was no vaccine, so people were just very resigned to this terrible disease sweeping through The Philadelphia school was substantially protected from this measle's outbreak by these ultra violet lamps. And you know, this was not

stuff they did in secret. This was all heavily reported. People were very excited. They were like, wow, we'd maybe we don't have to worry about a new nineteen eighteen flu pandemic again, because we know that influences airborne and we have a way to protect ourselves from it. And yet nobody knows who the Wells is are these days. They just they crashed into obscurity later on, so you know, they might not have died in a plane crash like fred Meyer, but they had their own crash Nevertheless.

What were some of the factors at play there?

compelling evidence. And so you know, if you're talking about water, like let's say that sewage is flowing into a river and a city is getting its drinking water supply just downstream, and there are a bunch of typhoid cases like this

literally happened in Lowell, Massachusetts in the eighteen nineties. You can you know, you can say like, hey, let's stop getting our drinking water from there, shall we, and then lo and behold the typhoid goes away, you know, like so that there's a certain sort of control to that, whereas the air is like it's very hard to control. It's elusive, and while there is a lot of life

in the air, like it's it's dilute, you know. So you might be breathing, you know, two thousand times a day, hundreds of thousands of times a month, but you know, it could just take one of those breaths for you to take in COVID or what have you, and boom, You've got an infection. So I'll just say it is hard to study. But you know, on top of that, I think there was this consensus that had really built in and people were very reluctant to shift away from it.

So they just they would say, like, you need to really really persuade me that diseases can be airborne. So they really refused to look at good evidence. And yeah, and I think with the with the biological warfare research, it's arguable that a lot of the best evidence that diseases are in fact, airborne was being done in secrecy, right. It was being done you know, as classified research, and

some of that is still classified today. So instead of being an open science, a science that was really like focused on human health and you know, and understanding ecosystems, a huge amount of effort in the air biology world went into building weapons. And so maybe people thought like, well, I suppose you could build a weapon that could really create an airborne disease, but that you need human intervention as opposed to just nature. So there were a lot

of different a lot of different reasons. But what's remarkable is that even at the start of the COVID pandemic, a lot of these assumptions and a lot of these misunderstandings and so on that you can trace back a century were still present in public health guidelines. Yeah, and how and how public health organizations dealt with the COVID pandemic, they were still in place, right.

or sing, and they can float. So those big droplets they drop to the ground because they're so heavy, the thinking was, But in fact, there's all these tiny droplets which can themselves have covid viruses or influenza viruses or you know, tuberculosis bacteria in them, and you know, they can fill a room if it's not well ventilated. They can fill a room like smoke. Think of those as viruses.

William and Mildred Wells. Like these people were like, h I keep seeing these references to William and Mildred Wells, Like who are these people? Like nobody knew who they were. And I talked to this one University of Hong Kong researcher, a named Hugo Lee, who is just a you know now is like a world expert on airborne and at the time he was trying to help understand SARS and he was like, h it looks like Wells has written a book. Wells wrote a book in nineteen fifty five.

Nobody in Hong Kong had it, and the only place he could find it was in one university library in the United States, and he asked them to photocopy it. This is like the early two thousands. They so they photocopied the whole book for him and they mailed it to him. And then so he gets this big stack of photocopied pages and he starts reading it and he says, ah, okay,

now this is making sense. These are droplets, okay. And it's crazy to think that he had to go to these measures to discover what had been widely reported and widely known in the nineteen thirties. You know that he had to dig this back up, and thank goodness he did, because then he did a lot of research on SARS and really demonstrated how with the way he was spreading through buildings and hospital wards and so on, it really did look like it was behaving like what William and

Mildred Bells was talking about and airborne disease. The problem is, among other problems, is that SARS, it's sort of a good news band news thing. SARS was able to be controlled and then eradicated because all you needed to do is as soon as people showed symptoms, that's when they started becoming infectious. So you just be real careful about

isolating people, you know, supporting them. Some of them died, you know, about eight hundred people died of SARS worldwide, but they rained it in and there is no stars anymore. So it wasn't something that you could be sort of steadying year in year out. It was just this one terrible moment in history. And you know, there were these clues, you know, these studies that said like, hey, maybe this is airborne, but I yeah, I'd say that it didn't

really penetrate. You know, all the pandemic preparedness that came afterwards was all based on this idea that it would not be truly airborne.

or saying no, no, there's the evidence says otherwise. And so this group of people, at first just you know, just a couple dozen experts, they got together and they tried to change the world health organizations the view on this, who didn't budge. So then they went public. They started trying to like gin up support. But it really took like a whole string of outbreaks and studies on those

outbreak to really demonstrate it. I focus on one in particular that struck a choir in Washington State where on March tenth, twenty twenty, about sixty people gathered together one night to sing, and they were being careful, they were doing everything they were supposed to be doing, and no one seemed to be sick, no one was coughing, but there was an infected person who was breathing, and then you know, over fifty people came down with COVID in

the next few days. It took time, unfortunately, to sort of to become aware of these outbreaks and then for these airborne advocates to say, like, hey, we're going to investigate these as sort of cases of airborne spread, see if we can test this hypothesis. And then eventually enough evidence emerged that satisfied a lot of people, and then

the consensus shifted. I mean, I wouldn't you know, I'm there are people who will still say like, no, I'm not convinced, but you know, I would say like that most certainly most scientific societies that are relevant to this and so on, have all agreed that it's airborne. But yeah, it took a long time.

then you've got to do different things. For one thing, we might have made sure, really sure that we had a real stockpile of protective equipment, which we didn't, so you know, people were just desperately reusing N ninety five masks, which is crazy. We could have invested in ventilation systems in schools and other places. We could have had ultifilet

light in places where ventilation wasn't a good solution. I mean, you know, these advocates of airborne disease that they were saying in the summer of twenty twenty, like, we can get kids back in school this fall if we take airborne infection seriously, if every classroom has you know, at least an air purifier or something. But you know, the

ventilation of schools, unfortunately, is terrible. So I think across the board a lot of lives would have been saved if we had immediately responded to COVID, recognizing the possibility that it was airborne and acting on that.

spread through the air at least to some degree. What it hasn't led to has been real mandates. Like there's no country anywhere yet that officially has standards in place, you know, like if you're going to build a building, this is what you have to do to keep the air safe. Doesn't exist yet. If you walk into a building, you kind of expect that, you know, there are building standards about the rebar and the materials that they're used.

You know, you don't expect that they contain poisons that are going to walk through the air and kill you because there are standards, But there are no standards yet for how to keep the air clear of pathogens. They've suggested mandates, no one's taken them up quite yet.

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