Today, Explained - Surfaces vs. droplets vs. aerosols

Episode Date: July 7, 2020

239 scientists have signed a letter urging the World Health Organization to warn people about airborne transmission of the coronavirus. Professor Jose-Luis Jimenez, who helped write the letter, explains. Transcript at vox.com/todayexplained.  Learn more about your ad choices. Visit podcastchoices.com/adchoices

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Hey, Mom. Hi. How you doing? Good. I have amazing news. What? Today is the 600th episode of Today Explained. Oh, wow, Sean.

Pretty cool, huh? Yeah, time flies. Time flies. It was just, you know, February 2018 where we were making episode one. Like yesterday. Yes, like yesterday. Yes. And now we're in the 17th month of 2020 and it's episode 600.

Congratulations, babe. So we reached out online to ask people what they wanted to hear today. And a bunch of people asked to hear from you. Oh my gosh. Other people were like, play Freebird, and then other people said, please do anything but COVID and protests. Hamilton. You want us to do something about Hamilton?

Everybody's talking about it. But there is big pandemic news today, mom. I know the pandemic is pandemic, so what shall we do about the pandemic? Scientists are asking the WHO to stress how the virus lingers in the air. Oh, yes. I heard about it yesterday.

So you'll listen? Yes, of course. I listen to it every day. If you're there. So you didn't listen to what Noam hosted last week? No, I did listen to Noam. Thanks, Mom. It's been a rough week for the World Health Organization, and it's only Tuesday.

This afternoon, President Trump officially withdrew the United States from the WHO. The United States, as a reminder, is its biggest funder, and this is the middle of a global pandemic. This change doesn't take effect until July 2021, so you know, if someone like Joe Biden wins the presidency, he could for sure reverse the decision. But still, not a great day for the WHO. And this comes after a bunch of scientists published a letter calling the WHO out yesterday. Hundreds of scientists are calling for the World Health Organization to revise its recommendations on the novel coronavirus, saying that there is evidence that the disease is airborne. Airborne. I know. You know. We know.

But the WHO, in July 2020, is still downplaying the fact that this thing is lingering in the air. In an open letter to the agency, 239 scientists from 32 countries outlined evidence showing that smaller particles, which can glide the length of a room, can still infect people. Jose Luis Jimenez is one of the scientists who signed this letter to the WHO. Well, not only I signed it, I was one of the people who helped write it. He's a chemistry professor at the University of Colorado Boulder, and he's going to try and help us understand why the WHO would resist saying something so many of us already know.

We started with the letter and why he wrote it. Well, I started working with a group of scientists and we were concerned about the fact that we thought COVID-19 may be partially being transmitted through aerosols. So we reached out to the World Health Organization and we had a telecom with them and we exchanged several letters. And we were surprised to find that they were very resistant to this idea. WHO spokesman Tarek Cesarovic told Reuters that the agency is aware of the article and is reviewing its contents with its technical experts. So what exactly is the WHO's position right now? Their position is that transmission through aerosols can happen in a hospital during intubation when they are connecting someone to a ventilator

and the personnel that are doing that procedure could get infected. So they say that can happen. But they say outside of that situation, it's very, very unlikely. So it's not something really we should worry about or we should protect against. So what is it that you and your 238 fellow scientists have signed on to? What exactly are you hoping the WHO will start to share with people? We're hoping that they change their guidance and accept that aerosol transmission may actually be playing a role. And at the end, what we're hoping really is that we can be more effective at stopping the growth of the pandemic.

So it does appear that there's a lot of confusion about these aerosols. So let's just clear it all up. What exactly are they and how are they spreading? So aerosols are small particles that are suspended in air. And the aerosols that we're concerned here are respiratory aerosols. So when you breathe, it's known since the 1940s that when you breathe, there are particles that are coming out that didn't come in as particles. They're actually little pieces of your respiratory fluid that when the air is rushing out of you, it takes a little part of the fluid

that's lining your respiratory system and it comes out as a small particle or as many small particles. Now, if there is a virus that's infecting you and is on the surface of your respiratory system, those particles that come out can carry a virus. Now, the difference between the aerosols and what the WHO calls the droplets is that the droplets fall to the ground very quickly, like if you were spitting sand, and then they are no longer a concern. The aerosols don't behave that way. They are small enough that they stay in the air maybe minutes, maybe hours.

And then if you are in the same room with someone who's, you know, is producing, is maybe talking, is singing, is exhaling some of these particles. And then you breathe them in. Some of them may be logged into your respiratory system and cause infection. So the aerosols are not the droplets. They're their own thing. They're airborne particles that linger in the air. Do they linger if you're indoors, outdoors, both?

So the terminology is very confusing. An aerosol and a droplet are the same thing. They're just bigger and smaller. So here I'm using droplet in the way the WHO uses droplets when they talk about droplet transmission is important. Those are the kinds of things you can see? Is that fair? Yeah, yeah. So if you cough and you sneeze and then you see some droplets coming out, those are the droplets. Now, the aerosols are also coming out, but they are too small to see. Okay, but it is more of a problem indoors than outdoors. Is that fair? Yes, yes. And this is something very important, we think.

So we believe one of the reasons that the WHO has not been too keen on recognizing airborne transmission is because they fear panic. In the mind of a lot of people in the medical profession, when they hear airborne, they hear like missiles or like chickenpox. And these are diseases that if they find a population that nobody is vaccinated, is not immunized, they spread like wildfire. So then they are afraid that if people hear COVID-19 is airborne, they will think, oh, COVID-19 is like missiles. And it's not like that. COVID-19, we believe, is contagious through the air, but it's nowhere near as contagious as missiles. You need to help it along. So how can you help increase the chance of infection? Well, you can be indoors in a crowded location

with low ventilation for a long time when there is loud talking or singing and without wearing masks. Every single one of those things increases the concentration of respiratory particles that are in the room or increases how many you may breathe in and increases the chance of infection.

Are there really good examples where COVID-19 really spread through aerosol transmission? Yes, there is a number of outbreaks that have been studied and that we have written up that submitted for publication about the Skagit Choir event in Washington state. So this was in March 10th. Now this was early on in the coronavirus crisis, so large groups were still permitted. But they did all the things that they were told to do. They washed their hands. They stayed away from each other.

We greeted everybody at the door with hand sanitizer. Nobody did any handshaking or hugging. And it's known that there was one person that was infected to begin with, but another 52 got it in a two and a half hour rehearsal. And it's basically impossible to explain if it's not going through the air, because there is people who are 60, 70 feet away from this person who still got sick. And people got sick all over their room. There's no other way that it could have gotten spread except by aerosol from us breathing in and out and singing.

That's the case I know best, but there is another case that has been in the news a lot about the restaurant in Guangzhou, which is pretty clear that it has to have gone through the air. A new study says on January 23rd, the day Wuhan was locked down, a family traveled from there to Guangzhou near Hong Kong. The following day, they ate at a restaurant. What happened in this restaurant is it didn't have much exchange of air with the outdoors, so the air was stagnant. And they had some of these split air conditioning units that were recirculating the air only through a part of this restaurant.

And there were people in other tables that did get infected, even though they didn't touch any objects that the infected person has touched. They didn't talk to this person, so there was no chance that the droplets that this person was maybe emitting when speaking would have impacted on them. Less than two weeks later,

nine other people got the virus, five who were not seated at their table. Some of the people who got sick were more than 15 feet away. So the only explanation is that this had to have happened through aerosols. And fortunately, there was a camera, basically a closed circuit camera that recorded the whole thing. So then it was easy to verify that indeed there was no contact. So this is why that case is so valuable, because we have very good information about what happened. So we are able to rule out alternative explanations.

Do we have any idea what percentage of these cases are coming from surfaces, from big droplets, from smaller aerosols? Do we have any data yet after all this time? Not really. We have guesses, and I could give you my guesses, but I shouldn't. But I mean, I think the current understanding, and it will vary with different scientists, is that droplets are likely important, aerosols are likely important, and surfaces may be less important, but that may be less important. But that could change. I mean, I would say we should defend against all three.

I wonder, you know, the president made a big stink. He tried to blame the WHO for the spread of COVID-19. He said they mishandled this. They didn't hold China accountable sufficiently. Was he right on some level that the WHO sort of made a mess of this pandemic and could have handled it a lot better? When I hear you talking about them perhaps holding back information about aerosols because they don't want to scare medical professionals, I think, well, that's not their job, is it? I don't think, and I think we have been very clear internally, like a group of scientists doesn't want to do anything that could harm the WHO as an organization.

We feel they're essential, that they're doing an essential job and they're very difficult circumstances. So we definitely don't want to hurt them. In fact, we discussed our worst nightmare was that, you know, President Trump would pick up our letter and use it to criticize the WHO. And we want to try to convince them to change their position because we realize how important their advice is for many countries. And in narrower things of the science, they have been slow or they have been resistant. I mean, not just with aerosols, but some other things like the asymptomatic transmission

or things like that. But I don't think that has anything to do with China or has anything to do with politics. I think it has to do with an organization that's trying to do something very difficult in very little time. And yeah, so I don't think there is anything evil, nefarious or geopolitical conspiracies

that have to do with any of this. I believe in the sound More with Professor Jimenez after a quick break. I'm Sean Ramos for UM, it's Today Explained. I believe in the sound Even when it's not shining Even when it's not shining Support for Today Explained comes from Ramp. Ramp is the corporate card and spend management software designed to help you save time and put money back in your pocket. Ramp says they give finance teams unprecedented control and insight into company spend. With Ramp, you're able to issue cards to every employee with limits and restrictions and automate expense reporting so you can stop wasting time at the end of every month.

And now you can get $250 when you join Ramp. You can go to ramp.com slash explained, ramp.com slash explained, r-a-m-p.com slash explained. Cards issued by Sutton Bank, member FDIC, terms and conditions apply. Professor Jimenez, some of the country is staying safe and the rest of it is going to town. And it's sort of unsurprising considering the lack of leadership we have. What should people be keeping in mind with the aerosols and the lingering COVID in the air and what have you? Well, people should adapt how much they go out and all that, depending where they are. If I was in Texas right now or in Arizona, I would be very careful. Even if the state wants to reopen, I would try to be at home as much as possible. If I was in one of the states that are doing a better job, perhaps like in the Northeast, maybe I would take a little fewer precautions. But in general, what people have to do is to try to avoid or reduce

being indoors away from home, especially if it's crowded, especially if there is low ventilation, long time, people talking or singing loudly, and if there are no masks. You know, you still can go to the supermarket, but wear your mask, go there as quickly as possible, and so on. And then businesses or public organizations should be looking at their ventilation systems and see, OK, is there some way that we can maybe install a better filter, or we can change how much air we get from outside, or we can install some of these portable HEPA filters that are very effective at filtering the virus.

And those are all things that are not necessarily expensive and that we cannot do to reduce transmission. Because at the end, I mean, people say, oh, these lockdowns or the masks are an attack on my freedom. And what we've been saying is, well, you know what the real attack on your freedom is, is the virus. So we can do these things that we think are going to be effective as reducing the spread of the virus. That's what's going to give us the freedom. Let me ask you about a couple of real world situations people are encountering right now.

I recently went to the dentist for the first time this year, and I didn't really think about the elevator up to the dentist very much. If you get into an empty elevator, I wonder, is there a risk there if someone with COVID, for example, had sneezed in the elevator, I don't know, five minutes before? Or if they were talking in the elevator, there is some risk. It depends how well ventilated that elevator is. I mean, what I would say is if you can, you know, just wait. Let those people go down and then call the elevator again so that you give the air some time to be exchanged or see if you can take the stairs. You know, and I think there is some risk, but it's small.

The problem is if you are doing this day in and day out, and if you are going to places where people are not wearing masks and instead of one minute in the elevator, you're staying three hours in a bar and people are shouting because the music is loud. And, you know, you start accumulating some of these risk factors. What about planes? I mean, there's news that some airlines will now be flying once again at full capacity.

Is that wildly irresponsible? Is that safe? And should people be considering it? I think it's irresponsible. I mean, I've been talking to some friends and family who have been flying and they said, well, Delta is keeping the middle seats empty and is being very strict with the mask policy and United is putting people in the middle seats.

Guess which airline I'm going to fly, you know, if I have to fly. Delta, for the record, had no part in sponsoring this episode. Okay. But I mean, airplanes have very good ventilation systems and very good filters. So, you know, they're relatively safe. But the problem is if you are sitting next to someone who has COVID and is breathing out these respiratory viruses,

and then you're sitting next to them for a few hours, you could get it that way. And there have been outbreaks of respiratory diseases in airplanes. Typically, these outbreaks get people sick. If the sick person is in one row, the people who get sick are the ones in that row or one or two rows in front or the back, right? So reducing density of people in the plane, having the middle seats empty, that's definitely a good idea. And of course, wearing masks and enforcing that people wear masks. I think a thing I hear people constantly worried about with airlines is the recycled air,

the air is constantly just being reused. Is that true? There is a lot of recycled air, but my understanding from talking to other experts is that it is recycled, but it goes through very good filters. You know, then those viruses are most likely being caught in the filters and they're not coming back. Let's close out these scenarios with a Trump rally. He's been doing those again. I stand before you today to declare the silent majority is stronger than ever before. Yes, I actually ran a model simulation of the Trump rally. How did it go? Well, I was getting some contagion.

I did it before the Tulsa rally, and then I was getting some tents of people may get COVID out of the rally. But this was only through the aerosols when really, given that they were going to be in close contact and touching objects, there probably be more from other routes. But then there were many, many fewer people there than they were anticipating. So, you know, but there have been some news that there have been some cases coming out of the rally. Two new Trump campaign staffers assigned to Saturday's rally in Tulsa have tested positive for COVID-19. Overall, at least 18 members on the ground in Oklahoma have tested positive.

So a Trump rally is even riskier than an elevator or a plane because of proximity to aerosols and droplets, but also because of touching stuff, touching objects. In the outset of this, did we place too much emphasis on touching stuff, on surfaces, at the expense of aerosols and droplets? You know, it's hard to tell, and I'm not an expert on the surface transmission. That is what the CDC is saying now, though. I mean, the revised guidance as of a month ago or so, the CDC is saying that it is possible to get it through objects, but they don't think

that's what's driving the pandemic. You know, I personally keep washing my hands, keep washing the groceries and everything in the same way. My mother-in-law lives next to us and she refers to my wife and I as the military police who control you know her life and tell her what she can do and not and so she was saying you know can I go to the dentist just to have a regular cleaning and I said you know I don't think it's a good idea that's something that can wait and she said can I go to this doctor for some more serious health issue and I said yes you know that's a small risk but but the risk of not addressing that issue is more important. So I would say, you know, just try to minimize your exposure.

You cannot make it zero, but try, you know, go early in the morning when not all the people have been there. If you can, you know, wear your mask and try to make it as quick as possible. You know, do all these things to reduce your risk. Right. It's really tough. I mean, what do you say to people who are maybe not making jokes like you're in law, but really skeptical of the virus itself and then any of the recommended safety procedures? I mean, it's difficult to convince people. I mean, it's kind of like trying to convince people that climate change is real. There is people out there that there's nothing you can say, you know. Do you find it frustrating? I mean,

you're dedicating all of your work and all your time to trying to help people understand this virus. And in the meantime, there are like house parties and clubs and bars and beaches where people are just acting like this isn't happening. Yeah, yeah. I mean, it is frustrating. And, you know, my wife shows me pictures of this party or that party and my blood boils. But, you know, as scientists, what we can do is we can try to provide accurate information. So then, you know, politicians and others can give guidance that's credible.

And, you know, when they get questions, you know, about the masks, they can explain better why they need to be worn. Well, thank you for your work, and I hope you won't lose faith. Hopefully we'll come out of this and it won't take too long. Indeed. If I leave here tomorrow, would you still remember me? For I must be traveling on an island, but there's too many places I've got to see