Radiolab - Dispatch 4: Six Feet

Episode Date: April 11, 2020

Since the onset of the pandemic, we exist in a constant state of calculation, trying to define our own personal bubble. We’ve all been given a simple rule: maintain six feet of distance between yourself and others. But why six? Producer Sarah Qari uncovers the answer, and talks to some scientists who now say six might not be the right number after all.  This episode was reported and produced by Sarah Qari and Pat Walters. Support Radiolab today at Radiolab.org/donate.  

Wait, you're listening. Okay. All right. You're listening to Radio Lab. Radio Lab. From W. N. Y. C. See?

Yeah. Zara, Kari. Hello. Whoa. Hi. You're coming through so clear. This is crazy. It's pretty cool, isn't it?

Yeah. Hey, I'm Chad. I boomrod. This is Radio Lab. Corona Dispatch number four. This one is sort of a follow-up to our first dispatch. And it comes from producer Sarakari. In the last, I want to say, like, 48 hours,

I feel like I've become an armchair expert on how pathogens travel out of your mouth. Just to set it up. So, like, a couple days ago, I mean, it feels like 50 years ago, the whole group got together on Zoom and we started talking about numbers. At some level, like, I'm sort of obsessed with all the numbers that are, like, coming out every day. 22 people here and 500 people there. And I believe you had a question about numbers, a specific number.

Sure. Okay. A number that I've been thinking a lot about is six. The recommended distance is six feet apart. And you could be infected and spreading it to anyone in your six foot bubble. Do you mean like the distance we're supposed to stand apart from one another? Exactly. Six feet between all people is not a suggestion.

Yeah, it's funny now that you mention, I feel like we're all developing this new physical instinct for that distance. Like the other day I was at the grocery store and I felt and I could see other people feeling like we all had these six foot force fields around us and we were altering the arc of our walks so that we would go around each other's force fields. Yeah, totally, totally. And it made me wonder, where did this number come from? And is six actually even the right number?

Okay. You know, researchers are really interested in this question. So I called a bunch of experts that study this. How far do infectious agents like bacteria and viruses spread? One of them was Dr. Julie Fisher. Associate Professor of Microbiology and Immunology at Georgetown University. And when I talked to her... In the past, one of the big questions was...

I came across this history. It's a very strange area of research. The interesting thing about it, too, is that it's very very... much still evolving. Some of the older studies... Maybe the place to start is actually the 1930s. In the 1930s, there was this guy named William Wells, who was studying different diseases, and he made this discovery that, like, when you open your mouth, for example, like when you're

sneezing or you're coughing, right? Like, every time you do that, there's little particles that fly out of your mouth. And eventually we learned that those particles are flying out pretty much all the time. Just when you breathe? Not even when you sneeze? Yeah. Everything I'm going to say just sounds gross. People sometimes expel small amounts of moisture when they're talking, particularly if they're talking to someone very close up.

Wow, it's like little mouth rain. Yeah, exactly. Mouth rain. Droplets. Tiny droplets. Invisible droplets. Big a droplet. Regardless of what you're doing.

When you open your mouth and let out air, this is what's happening. Okay. What happens next is, like, over the next few decades, like, scientists get really interested in how this works. And one of the first things they get really curious about is the Common Cold. A lot of the research was done in England. At the Common Cold Research Unit at Harvard Hospital, Salisbury, there's literally a stream of people volunteering to catch cold. Right after World War II in Salisbury in the UK, these scientists got together a bunch of volunteers. You and guinea pigs have been living there in pairs for ten days at a time.

The place is often nicknamed the honeymoon clinic. Okay. Because they frequently recruited couples. Literally, they would offer people a 10-day all-expenses-paid vacation in the Salisbury countryside. Food is good and the life quite comfortable, they say. The only thing is, they're almost burned to have a cold. In many of them, volunteers were deliberately infected. Researchers would take a little bit of cold virus, put it in an eyedropper.

This is how they're given colds with drops in them. Shoot some virus up the honeymooners noses, and then they'd watch to see what happened. How easily did the people around them become infected? Did it require close contact? Could they just be in the same space? I don't know if that sounds like a honeymoon anymore. Totally. It sounds like a raw deal, but you'd be surprised, like, people at the time, like, found this so appealing.

People essentially just saw it as, like, an ideal budget holiday. Anyhow, jumping ahead a few years. in later experiments, not at this clinic, but in later experiments, they would have, you know, do things like, oh, have infected and non-infected people sit together and, like, play a game of cards for a bunch of hours, and then see, like, how the disease traveled from person to person. Oh, they'd have, like, sick people and healthy people play together and then see who got sick? Exactly. Also, they were quite interested in, like, when people are sneezing and coughing and, like, expel.

telling again these like droplets into the air, like how far are those traveling? And so one of the things that came out of these studies is that for the common cold, they found that the droplets, the droplets are going about three feet. That's where we came up with the three feet. And this is three feet not through contact. This is just the mouth rain. Right. So simply being within three feet of someone puts you in the blast radius of their mouth rain. Got it. For many, many years, that was the sort of raining, understanding that like if you're going to have a bubble around you, it should have a three-foot radius. But then scientists realize that three feet might not be enough. And the way that

they realize this is that in the early 2000s, when there are outbreaks of different kinds. 2000s, so this is recent. Yeah, yeah, it's pretty recent. So this week saw the galloping rise of SARS. When there are outbreaks of different kinds like SARS. And tonight as health experts prepare for a possible H1N1 flu outbreak? H1N1 or swine flu. Scientists and epidemiologists start to look at the patterns of how the disease is spreading. And actually one type of information that was really useful to these scientists. This source of information actually comes from a lot of times with the airliners.

So this is Dr. Albert Coe. I'm at the Yale School of Public Health. He's the chair of the epidemiology department there. So these are kind of these natural experiments where somebody has. as a respiratory illness, and they know how many seats in front and how many seats in back, as well as in the side that people got sick. Let's say you're an epidemiologist tracking SARS, and you discover that the person sitting in seat 29A has the illness. So then you track everybody else on the plane to see what happens

and later find out that the person in seat 27A ended up getting sick too. So then you measure the distance between seat 29A. and C27A, and it turns out to be more than three feet. And they found that the people who had most risk were, you know, waiting two rows before and two rows behind, which is about six feet. I see. So this is where it comes from. Yeah.

And so then the CDC looks at that, and they update their guidance based on that. Again, the assumption is that six feet is about the distance that a droplet can travel. And so now with the virus that causes COVID-19, SARS-CoV-2. Assuming that SARS-CoV is transmitted by droplets.

You can use that same rule. You know, it's interesting. As you were talking, I kept thinking about that idea of six feet under,

how we bury people six feet under the ground, which apparently we only started doing in the 1660s because of the plague to stop infections.

So it's interesting. It feels like kind of this through-line number that's somehow always been there when we talk about trying to prevent spread. Right, but that number is evolving.

Hi, this is Zachary Ellis calling from Western Massachusetts where I'm celebrating my birthday in quarantine. Radio Lab is supported in part by the Alfred P. Sloan Foundation, enhancing public understanding of science and technology in the modern world. More information about Sloan at www.sloan.org. This is Radio Lab. I'm Chad I, Boomerad, here with Sarkari. we've been talking about the six-foot rule when it comes to COVID-19 and how just over the past week or so, that rule

we've been telling people six feet might be evolving. But now they're saying six feet may not be enough. The six feet may not be enough to prevent the spread of COVID-19. Health officials point to a Washington state choir practice where no one shook hands. 45 people were infected and two singers died. In order to have what people call this kind of large droplets spray transmission, you need to be facing the person.

And the way I've seen choirs sing is they're all facing the same direction. This is Lindsay Marr. Professor of Civil and Environmental Engineering at Virginia Tech. She studies how diseases spread. And she says that that choir anecdote, where you have people just singing together and then a bunch of them getting sick. I've gone through all the different scenarios in my head. And really the simplest explanation is that it was being spread through the air.

Meaning not through droplets at all. or at least not through the droplets that fall to the ground. See, we've known for a while that the mouth rain that comes out of your mouth when you talk, the drops come in different sizes. There are the big droplets. Kind of larger droplets, you know, that you can see almost with your visible eye or under a microscope. But those aren't the only ones. Now we know that there are ones that are much smaller than that.

That as you talk, there are thousands of these tinier droplets that also fall out of your mouth. That really we can only detect using modern equipment. And they're so small, like sometimes 150 at the width of a human hair, that instead of falling, they float. In these little mouth-thrained mist clouds. We now have the ability to detect viruses in these very small particles in air. And have we been able to measure that? I mean, do we know for sure that the virus that causes COVID

can travel in those airborne particles? And if it can, do we know how far it can go? Well, bear in mind that no one even knew that this virus existed until, you know, roughly three and a half months ago. This is Ed Yong, science writer for the Atlantic magazine. You know, in many cases we're sort of starting from scratch. But, you know, a study came out in the New England Journal of Medicine. In mid-March. Showing that the virus could remain stable in airborne particles for,

an hour or perhaps even more, although, as many people have pointed out, that was quite an artificial experiment. It was done in the lab, and it just wasn't clear exactly how it applied to real life. You know, it was evocative, but it wasn't a slam-done case. But then... There was a study that came out, maybe it's just a pre-print still, but they collected air samples at the University of Nebraska, which has one of the hospitals in the U.S. that's specially designed for handling dangerous airborne pathogens.

This study by the University of Nebraska Medical Center was really important. They found virus more than six feet away from the patient. They found it out in the hall. Wow. So the virus is definitely traveling that far in air. Well, you know, maybe not. I think that the reality of that situation is that, you know, we were going in and out of the rooms. So the likelihood is that we were bringing it with us when we were going in and out.

This is Joshua Santarpia. And I am an associate professor of pathology and microbiology. at the University of Nebraska Medical Center. He's the guy who led the study, and he says that when coronavirus first hit back in the winter, for people at his hospital... It got real, really fast. Hundreds of passengers quarantined over coronavirus

on the Diamond Princess cruise ship are preparing to leave. Our first COVID-positive folks came from the Diamond Princess. That cruise ship that was quarantined in Japan back in early February. They asked us to take 13, and it wound up being a total of, I think, 15. In addition to treating these people, Josh and his team went in and swabbed little spots all over their rooms and took samples from the air, looking for the virus. I was a little surprised by how much we found. Josh says that he doesn't think that the virus floated down the hallway on its own. Based on this particular study, it's hard to say how far it went, but we found evidence of virus in and around their entire room.

Not only on things that people touched. Their remote controls for their television. But also in the air. Just floating around. And landing in all of these nooks and crannies around the room? The air handling greed. Under the bed. On the wall.

There wasn't a single kind of sample that we took that didn't have some evidence. And these are intact viruses that you're finding, ready to jump into somebody and make them sick? No. One thing to point out here is that the evidence of virus that Josh found isn't like actual live virus. Yeah. So it was viral RNA in those samples. What they find instead are traces of the virus's genetic material,

which is more like finding the fingerprint of a suspect, which suggests that they were once there at the crime scene, but might not actually be there any longer. It could be that the virus floated down and then landed on a surface and then disintegrated. Like, we know that the virus eventually falls apart in the environment. But the thing is, like, even if it had been intact, Josh says that he can't really tell yet if the viral spillage that he's seeing around the room is enough... To, you know, to be capable of causing infection.

Like, was there actually enough live virus floating across the room in order to make somebody sick? Yeah. Have you made any attempt to figure out how far viruses that could make someone sick can float? So that's the question that I'm currently trying to answer with the work that we're doing now. For now, Josh says he doesn't really know. It seems like it's more than six feet. But is it 10? 15, 20?

Nobody knows. I personally have been using a 10-foot rule, and the farther the better. Interesting. Okay. So if you think about someone who's smoking, when you're close to them, there's the cloud of smoke. But as, you know, as that smoke disperses eventually like a 20, 30, 40 feet away down the block, it's, you know, it's not a dense cloud of smoke anymore. So the same thing, viruses behave in the same way in the air. Well, that's interesting. That gives me a visual.

Yeah. That does make me wonder, do you, I mean, do you hold your breath? I mean, in theory it should help. I've done that when I've run past someone. I'll hold my breath for a few seconds. I don't know if it makes a difference, but in theory it could. The thing that makes the most difference, and like every expert that I talked to without fail reminded me of this,

is just not going anywhere. Unless you absolutely have to. Don't worry about the six feet. Just keep that number as high as you possibly can. And if you do have to leave, and, you know, a lot of people do, just wear a mask when you go out. Because regardless of what kinds of particles the virus can travel on, whether it's droplet or smaller airborne particles,

and frankly, regardless of how far it can travel on those different types of particles, if you've got a mask on, it's going to stop a lot of those particles from going anywhere. And on top of that, Ed Young says, The masks are not just a medical device, they are also a social device. He says wearing a mask sends a message. And I think the messages they send depend very much

on how many people are wearing them. Hey, podcast, people. I'm going to be on your podcast. Hey, Emil, help me count. How many people in here did you see? wearing a mask. I definitely saw one walk by here. If only one person is wearing a mask in a society that traditionally doesn't wear masks, it's very easy to think, oh, that's a little weird.

Whereas if everyone is wearing masks, it starts becoming more of a sign that we are all in this together. We want to protect each other. We count ourselves. Yeah. Oh, 19, 20, 21. I can see, wait, no, 22, 23. Ah, let's see.

Probably like three, a two-thirds, or three-quarters, actually. Do you think so? Okay, I think that's good. Let's go check out. Even if that effect is small, I think that is a powerful signal. Let's go to number 15. So, I think from now on, that's the number I'm going to start paying attention to. Producer Sarakari.

This piece was produced by Sara with production and editing by Pat Walters. Special thanks to Lydia Buriba and Julie Fisher for their expertise and, of course, Amil Aboumrod for his counting assistance. I'm Jad Abumrod. Stay safe, everybody. Hello, this is Haman Kim calling from Seoul, South Korea. Radio Lab is created by Jad Abumrad with Robert Crullidge and produced by Soren Wheeler. Dylan Keefe is our director of sound design.

Susie Legendberg is our executive producer, and her staff include Simon Adler, Becca Bressler, Rachel Cusick, David Gable, Bethel-Hapti, Tracy Hunt, Matt Kilty, Annie McEwan, Latif Nasser, Sarah Quarry, Ariane Wax, Pat Walters, and Molly Webster. With how from Shima Oliyae, W. Harris, Fortuna, Sarah Sanback, Melissa O'Donnell, Tad Davis, and Russell Gregg. Our fact checker is Michelle Harris. Thanks.