Part 1 - Why Worry About Airborne Transmission - The Science of COVID-19 Safety for Coffee Businesses
While we were measuring the impact COVID-19 has on the Specialty Coffee industry during our recent survey project, one clear fact came through: understanding COVID-19 science and safety is key in order for coffee businesses to survive.
Here we share Why Worry About Airborne Transmission - Part 1 of The Science of COVID-19 Safety for Coffee Businesses. This first segment of the second video in our Community Impact of COVID-19 series This first part includes general mechanisms for respiratory virus transmission and includes some examples. This part and the rest of the video features Professor William D. Ristenpart of the UC Davis Coffee Center, a chemical engineer in “transport phenomena,” meaning that he studies transport—fluid mechanics and aerosol science. Aerosols are suspensions of small solid particles or liquid droplets in the air and is therefore very relevant to COVID-19 transmission.
Prof. Ristenpart has published many articles in prominent scientific publications on COVID-19 transmission and prevention. He is also a coffee scientist, who has worked with the SCA on a number of research projects. With this background, he’s well-equipped to share information over respiratory virus transmission and what coffee businesses can do to keep their venues safe.
Prof. Ristenpart will address coffee houses and food retail concerns related to COVID-19 and steps businesses can take that are based in science, to prevent the spread of the virus through four actions: masks, ventilation, air purifiers, and limiting exposure.
A Live Q&A with William D. Ristenpart will follow the video on Thursday October 15 at 8am PDT/4pm BST.
Full Transcript (Part 1)
Hello everyone, my name is Bill Ristenpart. I'm a Professor of Chemical Engineering at the University of California, Davis and the director of the UC Davis coffee Center. And I'm delighted to be here today to share with you this presentation entitled “Coffeehouses and COVID-19, a tutorial on the science of airborne disease transmission and how to safely run your café.” And so my goal with this presentation is to share a really plain English, easy to understand and follow manner, the current scientific consensus on how COVID-19 is spread and what you as members of the coffee industry or as members of other small retail establishments, how you can protect yourself, your employees, your customers, from the threat of COVID-19.
And before I get going, I'd like to first acknowledge the very generous support of the Specialty Coffee Association who are helping to distribute this video, and also Pacific Foods Barista Series, who provided some financial support to make this all happen.
1:15 | An outline of the full series
In terms of an outline for what will be going through today, there are four parts to this presentation. The first one is: Why even worry about airborne disease transmission? There's a lot of confusion out there. My goal is to help clarify some of the issues here. Part two is really zooming in on a really key question: How does the virus get into the air in the first place? Again, there's a lot of misconceptions. One of my goals is to help show that this type of cartoon that I'm showing here is kind of misleading, and we'll talk about the details of that in part two and part three. Then we'll talk about what controls the transmission probability in your coffee house, in your establishment. That's really key question. After this virus gets into the air, what can you do to prevent that? You need to understand what effects that transmission probability. We'll talk about that in detail, in part three. And finally, in part four, we'll end with a bunch of specific concrete action items that you can take in your coffee house, to really make it safer for you, your employees, and your customers.
2:18 | Why is an engineer talking about airborne disease transmission?
So with that, let's get into it. Part one. Why worry about airborne disease transmission? Just to begin with, I think I should give you a little bit more background about me. Why is an engineer up here talking about airborne disease transmission? And so, in terms of who am I, I am a chemical engineer with expertise in something called transport phenomenon. Transport phenomena. And so, and that's really important, for example, in coffee science. I'm a huge fan of coffee. I love coffee. A few years ago, a few of my colleagues and I got together and formed the UC Davis Coffee Center. And here on the screen you see a few images of representative research we've been doing. In terms of transport, what does that mean? Transport to an engineer talking in the context of coffee, means, for example, how do molecules of caffeine get out of the solid coffee grounds into the liquid that you drink. That's an example of transport. And so I'm not going talk about this in great detail in this presentation, we have lots of other talks online where you can see some of my coffee research. The point I'd like to illustrate here is that transport phenomena is also really important in infectious disease transmission.
And just to show that I have some experience in this, here's a few of the articles that I've published in the past few years focused specifically not on coffee, but on airborne disease transmission. So in the top left here is the title: “Comprehensive breath plume model for disease transmission via expiratory aerosols.” On the top right, “Aerosol emission and super-emission during human speech increases voice loudness.”
Here in the bottom left, one focusing specifically on COVID-19, “The coronavirus pandemic and aerosols.” Does COVID-19 transmit via expiratory particles? And in the bottom right, here's one focused on influenza: “Influenza virus is transmissible via aerosolized fomites.” And so that's just a few papers that my colleagues and I have written in the past few years. The first one that I wrote in 2012, the most recent one came out two weeks ago in Nature Communications. And you might be looking at these titles and thinking, “oh my gosh, there's a bunch of words there that I don't understand.” And that's OK. We're going to go through them here, here in detail.
But just to really drive home, why do engineers think about airborne disease transmission? Let's take a look at this cartoon schematic right here. And so, on the left, we have a cartoon of somebody who's infected. Okay. And you can see there's like little red dots inside the lungs there that represent some type of viral pathogen. And, on the right, we have somebody else, a susceptible individual. And so when people think about disease transmission, they might think of these categories of disciplines on the slide. And so just going through them, I think most people are familiar with physicians. Those are doctors. Doctors study the diagnosis and treatment of disease for individuals. Alright, when you go to the doctor, that's what's happening. You probably heard a lot about epidemiology during the course of the pandemic, epidemiologists study distribution and causes of disease, not for individuals but for whole populations. And then for viruses, the people who study that for living are called virologists, there on the left. What does a virologist do? They study how a virus reproduces and grows within a host. And then an immunologist here on the right. Immunologists study the immune response. Your body fights off pathogens. And the immunology is a really complicated topic.
But I'm an engineer. Where do engineers fit into this picture? Well, engineers are right here in the middle. Alright, that virus, that pathogen has to get from the infected individual to the susceptible individual somehow. And engineers play a huge role and understanding the fluid mechanics and the aerosol science of airborne disease transmission. Literally, that pathogen has to get through the air somehow, and that means you necessarily need to understand how fluid moves. And we have to know a little bit about aerosols. And so a lot of you might be thinking like, “well, wait a second, what is an ‘aerosol’?” Okay? And that's a perfectly valid question.
6:14 | What is an aerosol?
Here's a picture of what most people think of. Here's somebody spraying an aerosol, hairspray or something like that out of a can. Okay. And so a lot of people think, oh, aerosols come out of a spray can to an aerosol scientist. You might look at this picture instead. Alright, so here's a couple people sitting in a café, in a coffeehouse drinking cups of coffee. And a lot of people would not look at this picture and immediately think aerosols. An aerosol scientist would, and why is that? That's because there are aerosols in the air everywhere. Alright, and so here these red arrows represent there are aerosolized particles floating around the air being emitted out of the coffee being emitted out of the people themselves.
And so what is an aerosol? Here's a definition: Aerosols are suspensions of small, solid particles or liquid droplets in air. And by suspension, we mean they're floating around in the air. And here's the key thing. Some aerosols are known to carry infectious pathogens, including COVID-19.
7:21 | How can coffee shop culture survive COVID-19?
And so now, this point I was, I was describing this concept of aerosols being everywhere to a café owner a couple weeks ago, and they got really depressed looking and they sort of think, “oh my gosh, if there's infectious aerosols everywhere, how, how can coffee shop culture possibly survive COVID-19, and the pandemic?” And that's not unreasonable question. And the reason I don't think it’s unreasonable is that you can go online and find lots of examples of articles like this.
Here's one from WebMD with a title, “Will coffee shop culture survive COVID-19?” And if you go through and read the article, it's a bit scary. You know, “the days of lounging in comfy chairs or tables inside coffee shops appear to be a thing of the past.” And so that, that can be pretty depressing are like right now we're stuck in this pandemic. A lot of coffee houses and cafés are closed. It's not unreasonable to think, “oh my gosh, you know, is, is that all over?” And I'd like to say right now that this is not a doom and gloom presentation. I'm, I'm very optimistic and I'm confident that we will get past this. Coffee shop culture will return. And the reason I can say that with some confidence is that we've gone through all this before.
8:28 | We’ve gone through this before.
And what do I mean by that? Some of you might have heard discussion about the 1918 flu epidemic. But actually, you can actually go back further in the past. And here's some pictures of a pandemic that occurred in 1665. So here there was something called the Great Plague of 1665 in London. That was the Black Death pneumonic plague that spread in part through the air. And so there's a great book, if you're really into this type of thing, I'd recommend you pick up this book. It was written by Daniel Defoe, who was the same person who wrote Robinson Crusoe. But there's a few quotes here that I think are really interesting. As far as I know, this is the first historical reference that link specifically airborne disease transmission and coffee houses. And so here on the top right there's a quote. This is a rule, there is a prohibition in very flowery 1600s language that “disorderly tippling in taverns, ale houses, and coffee houses” basically be prohibited. So “tippling” is an old-fashioned word for drinking. Okay. And if you read the rest of quote, it talks about how there's a curfew. And there were really trying to enact what we would use in modern language, social distancing by prohibiting people from coming together in coffeehouses.
And so another great quote from this book is down at the bottom. “Many people talk with the air being corrupted and infected.” And what that refers to is that there was tremendous confusion back then about how the plague was spread. Here in this quote, there talking about the air itself is corrupted therefore, what we do doesn't matter so much. Other people strongly held the view that you need to avoid individuals. And this quote here is great. Quotes somebody saying, “I never came near any infected body, but I got it anyways.” And so back then they had a very poor understanding of how diseases spread. And so I know that you're listening to this now for historical thing, so let's zoom in now.
One benefit we have in 2020 is we have a much better understanding of airborne disease transmission. And so here's a picture of a modern coffee house. This is what I imagine most of you care about. And I love this picture. This is actually Mishka's Café in downtown Davis, California. I've spent a lot of time there, had a lot of delicious coffee, written a lot of papers there. And I think I'm really motivated by the idea of how do we understand how to minimize disease transmission in this setting right now in 2020?
10:54 | How do pathogens spread from one individual to another?
And so to answer that question, we need to understand how do pathogens spread from one individual to another? And so here on this slide are listed several general mechanisms for respiratory virus transmission, specifically respiratory virus transmission, which is things like influenza and specifically COVID-19.
And so on the top we have two so-called “contact modes.” Contact modes. And we heard a lot about this in the very beginning of the pandemic when there was a lot of emphasis on handwashing. And so there's two contact modes, one is direct, and here we have picture of two people shaking hands, the idea is one person gets virus on their hand, and then you shake hands with the other person. And now you have it on the second person's hand and then they touch their face and it gets into the respiratory system and they're infected. That's called “direct transmission.”
The other type of contact mode is “indirect transmission.” And there's a fancy word here, “fomite.” And so here the idea is somebody gets virus on their hand. And then the touch, for example, a doorknob. Okay, then the leave and somebody else comes along and touches the doorknob, and now they have it on their hand. So that's indirect transmission. The word fomite refers to the solid surface that was contaminated. So here the door knob served as a fomite, but anything that's a solid surface can be a fomite, It can be a toy, it can be a countertop. It could be a coffee mug. Okay.
So early on, like I mentioned, there was a lot of concern about this. What I'd like to point out is that now there's a lot of evidence pointing to airborne disease transmission as actually being the main route by which COVID-19 is transmitted. And so there's several different types of airborne transmission. And the pictures here on the bottom indicate those.
The first one, here's a picture of somebody sneezing and you can hear references to “droplet transmission,” okay? And hopefully this is pretty intuitive. If somebody's infected sneezes in your face, right? You're going to get coated with the droplets, you might breathe some of them in. You might touch your face and then get contaminate yourself that way. That's droplet transmission.
The second mode, and this goes back to our definition of aerosols, is so-called aerosol transmission. And so this looks similar here, a picture of somebody breathing something out. And here this is a picture some actually exhaling on a cold day, so you see kind of a cloud of very small, tiny droplets. Okay. And so that picture, and both these pictures are, as I'll talk about in part two, are actually a little bit misleading because it turns out that many of the infectious particles that are emitted, both in sneezing and in aerosol emission, have nothing do with these droplets that you can see. All right, we'll talk about that in part two.
But just to finish the picture here, the third means of airborne respiratory virus transmission, here in the bottom right is something called aerosolized fomites. And you might also hear references to this as “re-suspended dust.” And here's the idea is if you have a contaminated surface, for example, if you have a contaminated Kleenex, okay? If you do something to aerosolize the particles, the dust, the virus itself can be carried along with dust.
So these are five general modes of transmission two contact modes, three airborne modes. A really, really important concept is that the epidemiological contact tracing that you've heard a lot about that can tell you when you likely got infected. It can tell you who likely infected you, but it doesn't tell you anything about how you got infected. So all the evidence for one type or mode of transmission versus another, it all has to be indirect. When somebody shows up at a hospital if they're infected with COVID-19, it's close to impossible to tell how that virus got into that individual. Alright, so we have to rely on indirect evidence.
14:55 | Why aerosol transmission is likely a main airborne transmission of COVID-19
There's a lot of indirect evidence now pointing towards aerosol transmission as one of the main mechanisms for airborne transmission of COVID-19. And so let's, let's talk a little bit about some of that indirect evidence. And so here on this slide is a report that dates back to March of 2020. And certainly, when I saw this, and a lot of my colleagues in the scientific community saw this, this one news report convinced us that there was a huge threat for aerosol transmission. And so here's the title of the press report that I first saw. The LA Times, “A choir decided to go ahead with rehearsal. Now dozens of members have COVID-19 and two are dead.”
And so on the bottom left here is a schematic from scientific case report for this published by the CDC. They went and carefully showed that there was basically one weakly or asymptomatic individual who ended up infecting 87% of people who attended a two and a half hour choir practice. And why this was so convincing is that this was after the pandemic, after those much concern about the pandemic spreading, much media coverage about the need to wash your hands and stuff.
So on the right, I've put a quote long quotation from the LA Times article: Sixty singers showed up. A greeter offered hand sanitizer at the door, and members refrained from the usual hugs and handshakes. After two and a half hours, the singers parted ways. Nearly three weeks later, 45 are diagnosed, 19 are ill, 3 hospitalized, 2 dead. And here's a key quote:
“The outbreak has stunned county health officials, who have concluded that the virus was almost certainly transmitted through the air from one or more people without symptoms.”
And so why this one report was so revealing was that they weren't doing the contact mode. They were refraining from shaking hands. If you go into the CDC report, you can see that there is some possibility that, you know, they had a coffee break. They might have touched some surfaces. But there was such a huge number of transmissions that this really suggested to at least the engineers and the aerosol science and infectious disease transmission, meaning that there was a grave concern, grave potential for aerosol transmission.
And so that was a choir practice. And there's actually been now lots of instances, lots of reports of outbreaks of COVID-19 associated with places where there's lots of singing, California actually banned singing in indoor locations. What about coffeehouses? And more generally food retail? The short answer is yes, there have been outbreaks that implicate aerosol transmission in coffeehouses, in food retail. Here on the left is a outbreak that occurred in a restaurant in Guangzhou in China. And here you can see the title, “COVID-19 outbreak associated with air conditioning in restaurant, Guangzhou, China, 2020.” And the schematic here shows that there is one asymptomatic individual and they ended up infecting about nine other people that later video evidence showed they did not directly interact with except for sharing the same room air. And so in part three of this presentation, we'll talk about this outbreak in detail.
So that's a restaurant. What about coffeehouses? Here's a very recent one. And just to show you how things, how quickly things are going now, I started making this presentation and then this outbreak occurred. But here's a report from South Korea. Here's the headline, “Starbucks Korea cuts, capacity delays promotion after COVID-19 cluster.” Ultimately one infected individual who was sitting in front of the air-conditioning unit inside of a Starbucks outside of Seoul, Korea ended up being responsible for about 56 infections with COVID-19. And again, the implication there was that there was aerosol transmission.
And so those are a few examples of airborne disease transmission. And again, all the evidence is indirect, but there's a lot of indirect evidence suggesting now long-range airborne disease transmission. And here on this slide, what I'm trying to really illustrate is that, within the scientific community, at least, there is a very strong consensus that we need to be worrying about airborne disease transmission. And so up on the top left here is a New York Times editorial by Linsey Marr. She is an engineer at Virginia Tech University. The title I think speaks for itself, “Yes, the coronavirus is in the air.” Below that is a great article by Shelly Miller. She's an engineer at University of Colorado Boulder, also talking about infectious aerosols transmitting COVID-19. There's a few other reports here in Nature and Science. For those of you don't know, those are the, arguably, the top scientific journals in the world. And there's a very powerful paper written by Lydia Morawska and Don Milton, down there at bottom, “It is time to address airborne transmission of COVID-19.” That's associated with a letter that more than 200 scientists around the world wrote to the World Health Organization saying, “look, the evidence is very strong. We need to think about airborne disease transmission.”
And most recently, just this, just last week—I’m shooting this video here on September first—last week, last week of August, there was a virtual workshop hosted by the National Academies of Science, Engineering, and Medicine titled, “Airborne transmission of SARS CoV 2.” That's the virus that causes COVID-19. And so there's two days’ worth of recorded presentations and panel discussions. I had the privilege of serving on one of the panels where leading scientific experts from around the world talked about the evidence for airborne disease transmission. And there was a very strong consensus that there is indeed airborne transmission and we need to inform the public and we need to develop research and recommendations to fight against airborne disease transmission. And so for those of you who don't have 14 hours of time to watch that whole workshop, my goal here is to condense the cutting edge research down into about a one hour four-part presentation today.
And so hopefully in part one, I've convinced you that we do need to worry about airborne disease transmission. And in the next part we'll talk about a key question: How does the virus get into the air in the first place? It's more complicated than you think.
The Community Impact of COVID-19 Survey
In the past half a year, SCA Research conducted two surveys to assess the impact of COVID-19 on the global specialty coffee community. One key takeaway we saw in our open-ended questions was a strong focus on worker safety, customer safety, and sanitary practices in light of COVID-19. Respondents mentioned the implementation of safety and health procedures more than any other tool as a key competency during reopening. 80% of respondents mentioned new cleaning and sanitation procedures being implemented. This takeaway was the reason for creating the second video in the series with William D. Ristenpart.
The first video presenting the survey results
In the first video in the series, Community Impact of COVID-19: An Introduction, Katie von der Lieth and Peter Giuliano analyze what the SCA’s most recent survey tells us about the general impact of COVID-19, changes in sales channels, lost sales to date, future revenue expectations, and business decisions around remaining close or opening back up for service.
Special Thanks to Pacific Barista Series
This series is made possible with support from Pacific Barista Series.
