JA: Sarah Qari?
SQ: Hello. Whoa! Hi!
SQ: You're coming through so clear. This is crazy!
JA: It's pretty cool, isn't it?
JA: Hey, I'm Jad Abumrad. This is Radiolab. Coronavirus dispatch number four. This one is sort of a follow-up to our first dispatch. And it comes from producer Sarah Qari.
SQ: In the last, I want to say, like, 48 hours, I feel like I've become a -- an armchair expert on [laughs] on how pathogens travel out of your mouth.
JA: Just -- 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.
MW: At some level, like, I'm sort of obsessed with all the numbers that are, like, coming out every day.
PW: 22 people here and 500 people there and …
JA: And I believe you had a question about numbers. A specific number.
SQ: Sure, OK. A number that I've been thinking a lot about is six.
[NEWS CLIP: The recommended distance is six feet apart.]
[NEWS CLIP: And you could be infected and spreading it to anyone in your six-foot bubble.]
JA: You mean, like, the distance we’re supposed to stand apart from one another?
[NEWS CLIP: Six feet between all people is not a suggestion.]
JA: Yeah, it's funny now that you mention it. I feel like we're all developing this new physical instinct for -- for that distance. Like the other day I was at the -- 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.
SQ: Yeah, totally!
SQ: Totally. And it made me wonder, where did this number come from? And is six actually even the right number?
JF: You know, researchers are really interested in this question.
SQ: So I called a bunch of experts that study this.
JF: How far do infectious agents like bacteria and viruses spread?
SQ: One of them was Dr. Julie Fischer.
JF: Associate Professor of Microbiology and Immunology at Georgetown University.
SQ: And when I talked to her ...
JF: In the past, one of the big questions was ...
SQ: ... I came across this history
JF: [laughs] It's a -- a very strange area of research.
SQ: The interesting thing about it too is that it's very much still evolving.
JF: Well, some of the older studies ...
SQ: Maybe the place to start is actually the 1930s.
SQ: In the 1930s, there’s this guy named William Wells, who was studying different diseaseas. And he made this discovery... Like, when you open your mouth. For example, like when you're breathing or you're sighing, every time you do that, there's little particles that are flying out of your mouth. And eventually we learned that those particles are flying pretty much all of the time.
JA: Just when you breathe, not even when you sneeze?
SQ: Yeah. Yeah.
JF: Everything I'm gonna say just sounds gross.
JF: People -- people sometimes expel small amounts of moisture when they're talking, particularly if they're talking to someone very close up.
JA: Wow, it’s like little mouth rain.
SQ: Yeah, exactly, mouth rain.
[NEWS CLIP: Droplets.]
[NEWS CLIP: Tiny droplets.]
[NEWS CLIP: Droplet.]
[NEWS CLIP: Invisible droplets.]
[NEWS CLIP: Bigger droplets.]
SQ: Regardless of what you’re doing, when you open your mouth and let out air, this is what’s happening.
SQ: What happens next is, like, over the next few decades, scientists get really interested in how this works. And one of the first things they get really curious about is the common cold.
JF: A lot of the research was done in England.
[DOCUMENTARY CLIP: At the Common Cold Research Unit at Harvard Hospital, Salisbury, there's literally a stream of people volunteering to catch cold.]
SQ: Right after World War Two in Salisbury in the UK ...
SQ: ...these scientists got together, a bunch of volunteers.
[DOCUMENTARY CLIP: Human guinea pigs have been living there in pairs for 10 days at a time.]
JF: The place is often nicknamed the Honeymoon Clinic.
SQ: [laughs] Okay.
JF: Because they frequently recruited couples.
SQ: Literally, they would offer people a 10-day, all-expenses-paid vacation in the Salisbury countryside.
[DOCUMENTARY CLIP: The food is good and the life quite comfortable, they say. The only thing is they're almost bound to have a cold, whereas ...]
JF: In many instances, volunteers were deliberately infected with influenza.
SQ: Researchers would take a little bit of cold virus, put it in an eyedropper…
[DOCUMENTARY CLIP: This is how they're given colds, with drops in the nose.]
SQ: ... shoot some virus up the honeymooners' noses, and then they'd watch to see what happened.
JF: How easily did the people around them become infected? Did it require close contact? Could they just be in the same space?
JA: I don’t know if that sounds like a honeymoon anymore.
SQ: 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.
SQ: Anyhow...Jumping ahead, a few years…
SQ: In later experiments, not at this clinic but in later experiments, they would have, you know, like do things, oh have infected and non-infected people sit together and play a game of cards for a bunch of hours. And then see how the disease has traveled from person to person.
JA: Oh they would have like sick people and healthy people play together and see who got sick?
SQ: Exactly. Also they were quite interested in, like, when people sneezing and coughing, and like expelling, again, these 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 the droplets, the droplets are going about...
JF: That's where we came up with the three feet.
SQ: … three feet.
JA: And this is three feet not through contact. This is just the mouth rain?
SARAH: Right. So, simply being within three feet of someone puts you within the blast radius of their mouth rain.
JA: Got it.
SQ: For many, many years that was the sort of reigning understanding that, like, if you're gonna 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 ...
SQ: … when there are outbreaks of different kinds.
JA: 2000s! So this is recent!
SQ: Yeah. Yeah, it's pretty recent. So ...
[NEWS CLIP: This week saw the galloping rise of SARS.]
SQ: When there are outbreaks of different kinds like SARS ...
[NEWS CLIP: And tonight as health experts prepare for a possible H1N1 flu outbreak.]
SQ: H1N1 or swine flu.
SQ: 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 ...
AK: This source of information actually comes from, a lot of times, with the airlines.
SQ: So, this is Dr. Albert Ko.
AK: I'm at the Yale School of Public Health.
SQ: He's the chair of the Epidemiology Department there.
AK: So these are kind of these natural experiments.
AK: Where somebody has 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.
SARAH: Let’s say you’re an epidemiologist tracking SARS. And you discover that the person sitting in seat 29A has the illness. So, you then track everybody else on the plane to see what happens and later find out that the person in 27A ended up getting sick too. So then you measure the distance between seat 29A and seat 27A and it turns out to be more than three feet.
AK: They found that the people who had most risk were, you know, within two rows before and two rows behind, which is about six feet.
JA: I see, so this is where it comes from?
SQ: Yeah. And so then the CDC looks at that and they update their guidance based on that.
JF: Again, the -- the assumption is that six feet is about the distance that a droplet can travel.
SQ: And so now, with the virus that causes COVID-19, SARS COV-2...
AK: Assuming that SARS COV is transmitted by droplets...
SQ: You can use that same rule.
JA: You know, it’s interesting as you were talking I kept thinking about that idea of 6 feet under. How, how we bury people 6 feet under the ground, which apparently we only started doing in the 1660s causes of The Plague. To stop infections. So it’s interesting, it feels like kind of this through line number that’s alway — that’s somehow always been there when we talk about trying to prevent spread.
SQ: Right but, that number is evolving.
JA: This is Radiolab. I’m jad Abumrad here with Sarah Qari. 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...
[NEWS CLIP: So this is, we’ve been telling people 6 feet...
JA: might be evolving…
[NEWS CLIP: But now they’re saying that 6 feet may not be enough?
[NEWS CLIP: That 6 feet may not be enough to prevent the spread of COVID-19…
[NEWS CLIP: Health officials point to a Washington State choir practice…
[CHOIR: LA, LA, LA, LA, LA…]
[NEWS CLIP: where nobody shook hands!]
[CHOIR: LA, LA, LA, LA, LA…]
[NEWS CLIP: 45 people were infected and two singers died.]
LM: In order to have what people call this large spray transmision you need to be facing the person. And the way I’ve seen choirs sing is they're all facing the same direction.
SQ: This is Linsey Marr.
LM:Professor of civil and environmental engineering at Virginia Tech.
SQ: She studies how diseases spread. And she says that choir anecdote, where you had people just singing together and then a bunch of them getting sick…
LM: 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.
SQ: Meaning, not through droplets at all.
SQ: 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 droplets come in different sizes. There’re the big droplets...
LM: Kind of larger droplets, you know, that you can see almost with your visible eye or under a microscope.
SQ: But those aren’t the only ones.
LM: Now we know, that there are ones that are much smaller than that.
SQ: That as you talk thousands of these tiny air droplets fall out of your mouth.
LM: That really we can only detect using modern equipment.
SQ: And they’re so small, sometimes one-fiftieth of a human hair, that instead of falling they float in these little mouth rain mist clouds.
LM: We now have the ability to, you know, detect viruses in these very small particles in air.
JA: And have we been able to measure that? I mean do we know for sure that the virus that causes COVID can, can travel in those airborne particles? And if it can, do we know how far it can go?
EY: Well, bear in mind that no one even knew that this virus existed until, you know, roughly three and a half months ago.
SQ: This is Ed Yong, the science writer for The Atlantic Magazine.
EY: In many cases we’re sort of starting from scratch but you know, a study came out in the New England Journal of Medicine…
SQ: In mid-March…
EY: ..showing that the virus could remain stable in airborne particles for an hour or perhaps even more.
EY: Although, as many people have pointed out, that was quite an artificial experiment.
SQ: It was done in the lab and it just wasn’t clear exactly how it applied to real life.
EY: You know, it was evocative but it wasn’t,a slam-dunk case.
SQ: But then…
LM: 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 US, that’s, you know, specially designed for handling dangerous airborne pathogens.
EY: This study by the University of Nebraska Medical Center was really important.
LM: They found virus more than six feet away from the patient. They found it out in the hall. Um..
LM: So the virus is definitely traveling that far in air.
JS: Well uh, 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…
JS:... we were bringing it with us when we were going in and out.
SQ: This is Joshua Santarpia.
JS: And I’m an associate professor of pathology and microbiology at the University of Nebraska Medical Center.
SQ: He’s the guy who led this study. And he says when coronavirus hit back in the winter that people at his hospital…
JS: It got real, really fast.
[NEWS CLIP: Hundreds of passengers quarantined over coronavirus on the Diamond Princess cruise ship are preparing to leave.
JS: Our first covid-positive folks came from the Diamond Princess.
SQ: The cruise ship that was quarantined in Japan back in early February.
JS: They asked us to take 13, and it wound up being a total of, I think, 15.
SQ: Iin addition to treating these people, Josh and his team swabbed little spots all over the rooms and took samples from the air looking for the virus.
JS: I was a little surprised by how much we found.
SQ: Josh says he doesn’t think the virus floated down the hallway.
JS: Based on this particular study, it’s hard to say how far it went but, uh, we found evidence of virus in and around their entire room.
SQ: Not only on things people touched…
JS: Their remote controls for their television
SQ: But also…
JS: In the air.
SQ: Just floating around. And landing in all these nooks and crannies of the room.
JS: Um, the air handling grates.
SQ: Under the bed.
JS: On the wall. It -- There wasn’t a single kind of sample that we took that didn’t have some evidence.
JA: And these are intact viruses that you’re finding? Like ready to jump into somebody and make them sick?
SQ: One thing to point out here is that the evidence of virus Josh found wasn’t like actual live virus.
JS: Yeah. So it was viral RNA in those samples.
EY: What they find instead are traces of the virus’ genetic material which is more like
finding the fingerprint of a suspect. Which suggests that they were once there at quarantine but might not actually be there any longer.
SQ: It could be that the virus floated down and came to rest on a surface and then disintegrated. Like, we know this virus doesn’t do well in the environment. But the thing is like, even if it had stayed intact, Josh says he can’t tell yet if the viral spillage that he’s seeing around the room is enough...
JS: To, you know, to be capable of causing infection.
SQ: In other words, was there actually enough live virus floating across the room to make somebody sick.
JA: Have you made any attempt to figure out how far viruses that could make someone sick can float?
JS: So that’s the question that I’m currently trying to answer with the work that we’re doing now.
SQ: For now, Josh says, he doesn’t really know....It seems like it’s more than 6 feet...But is it 10? 15? 20? Nobody knows.
LM: I personally have been using a 10-foot-rule. And the farther, the better.
SQ: Interesting. Okay.
LM: 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.
JA: Oh that’s interesting, that gives me a visual.
JA: That does make me wonder, do you, I mean...do you hold your breath?
LM: I mean, in theory it should help. I’ve done that when I 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.
SQ: The thing that makes the biggest difference -- and like every expert I talk to reminded me of this -- is just not going anywhere unless you absolutely have to. Don’t worry about 6 feet just keep that number as high as you can. And if you do have to leave, and lots of people do…
LM: Just wear a mask when you go out.
SQ: Because regardless of what kinds of particles the virus can travel on, whether it’s droplets or airborne particles -- and frankly, regardless of how far it can travel on those different particles, if you’ve got a mask on none of those particles are going anywhere. And on top of that, Ed Yong says…
EY: The masks are not just a medical device, they’re also a social device.
SQ: Wearing a mask, he says, sends a message.
EY: I think the messages that they send depend very much on how many people are wearing them.
EMILE: Okay podcast people I’m going to be on your podcast.
JA: Hey Emile, help me count. How many people in here did you see wearing a mask?
EMILE: I definitely saw one walk by here. So one.
EY: 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.”
EY: Whereas, if everyone is wearing masks…
EMILE: Nine, ten…
EY: It starts becoming more of a sign that we are all in this together, we want to protect each other.
EMILE: 16, 17, 18. We count ourselves?
EMILE: Oh. 19, 20, 21. I can see -- no wait, 22, 23. Uh let’s see, probably like three -- uh two-thirds or three-quarters actually.
JA: Do you think so? Okay, I think that, that’s good. Let’s go check out.
EY: Even if that affect is small I think that is a powerful signal..
JA: Let’s go to number 15… Hey, how are you?
SQ: So from now on, I think that’s the number I’m gonna start paying attention to.
JA: ...I think it’s gonna be a little bit like that except it’s gonna be for kids and adults. That one’s just for kids…
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