Vicki Hertzberg is a Professor at Emory University in the Nell Hodgson Woodruff School of Nursing, where she has founded and directs the Center for Data Science. Her research focuses on, “developing and applying statistical methods for the analysis of network data as well as microbiome data.” Specific topics include infectious diseases on networks, dynamic networks and microbiome of the airplane cabin.
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Rosemary Pennington: Some three-billion people fly each year, with many of them engaging in various kinds of rituals ranging from a preflight drink, to mindful meditation during takeoff. For some though, they’re flight prep includes drinking lots of water, getting lots of rest, and consuming enough vitamin C to ward off the dreaded post flight cold. The data of getting sick while flying is the focus of this episode of Stats and Stories recorded live in front of an audience in the Shriver Center at Miami University.
[Applause]
Pennington: I’m Rosemary Pennington and we’re in Shriver to celebrate the 10th anniversary of Miami University’s Department of Statistics. The podcast is a production of the Stats Department and the Departments of Media, Journalism and Film, as well as the American Statistical Association. Joining me in Shriver Center are John Bailer, the founding and current Chair of Miami’s Stats Department, and Richard Campbell, former and founding Chair of Media, Journalism and Film. Our guest today is Vicki Hertzberg. Hertzberg is biostatistics and bioinformatics professor at Emory University, and Director of the Center for Nursing Data Science. She recently co-authored an article that same out in the journal microbial ecology, which examined the microbiome of airplane cabins. Vicki, thank you so much for being here.
Vicki Hertzberg: Thank you for having me.
Pennington: Could you explain a bit why you and your coauthor decided to study germy airplanes, and what you found?
Hertzberg: Well, it goes back to the SARS epidemic in the early 2000s; we were approached by the Boeing Company. Boeing is in the business of selling airplanes, and part of the repercussions of the SARS epidemic was that one of the Canadian airlines went into bankruptcy proceedings. So, there’s – you know, you talk to many people and they say oh I always get sick when I fly, and so they really set out to understand more about what actually goes on on an airplane,
Richard Campbell: So, Vicki I flew to Minneapolis last month and about a week later I had a stomach virus. I’m getting ready to fly to Portland Sunday, so do you have any advice for me?
Hertzberg: Uh first of all, it’s probably not due to the flight.
[Laughter]
Campbell: I want certainty and I know that’s a problem in statistics.
Hertzberg: Here’s what I do, I get a window seat, I stay in it, I don’t get up I observe good hand hygiene and I don’t touch my face.
John Bailer: Very good. So, when you’re studying this, you’re studying a microbiome, what is a microbiome?
Hertzberg: The microbiome is those organisms that are all over the p;ace, but they’re small and you can’t see them. They’re on your skin, they’re in on or in your body and they’re also everywhere. So in this room it’s the bacteria, the viruses and fungi, and so we were interested to see what kind of bacteria, viruses and fungi were present on airplanes.
Bailer: So, you were looking at things like what is on the windows when you’re sitting by the window seat, or on the armrests, or on the table that you fold down? I mean, you were sampling all those different areas?
Hertzberg: We decided to sample air. So, we were seeing what was actually coming through the filters. And we also – or actually what was out in the space where passengers were seated, and we also were doing some touch surfaces, so we sampled the inside and outside of lavatory doors, and we also had two randomly selected seats on each of the ten flights that we took, and we sampled the tops and bottoms of the tray table and seat belt buckle.
Pennington: So how gross are planes?
Hertzberg: They’re no more gross than your living room. They look a lot like any other space that people spend a lot of time in.
Bailer: Did that surprise you?
Hertzberg: Yes, because you’re kind of conditioned to think that they will be kind of gross, but they’re no more gross than places you spend time. And we looked at a lot of other studies of the built environment. No one else has done airplanes, but there is a study on the international space station, and we looked at that. Lots of studies of classrooms and office buildings, and they are all very similar. Most of it is a skin bacterium called Propionibacterium acnes, and it’s actually what causes teenage acne, and that’s predominantly what you pick up in our sampling.
Bailer: So, are you saying that teenagers are the only ones that have to worry about flying?
Hertzberg: No no no no.
[Laughter]
Campbell: So, this topic is one of those topics that’s interesting to journalists, right? And you’ve done I think quite a few interviews about this, and I heard your episode with Ira on Science Friday, how do you think- what kind of a job do you think journalists do translating your work to the general public? And where is their work good, and what can they do better?
Hertzberg: I thought that they really – they would grab attention with headlines like germs on a plane, okay, and the point is that you want people to read the story. So even though I might have an intellectual objection to that, I get it I get it. But they did a pretty incredible job of reporting what we did and did not find. So …
Bailer: I would think that they would have been much more excited if there was a really juicy disease story embedded in this.
Hertzberg: They would have we took ten flights between Atlanta and various destinations on the west coast, so back and forth. We ran every environmental sample we got through the respiratory panel that Emory healthcare uses, and it has 18 viruses that it looks at: influenza A, pandemic influenza, influenza B, RSV, all kinds of things. And we never found a single positive result in something like 200 and some environmental samples. And we were flying mostly in what’s called the traditional flu season, between October and the end of March. And we checked and it was either the local seasonal epidemic, either in Atlanta or in the destination city for all of the 8 flights that occurred during flu season.
Bailer: So, I’m curious about the generalizing this result. So, if I’m travelling internationally, has this been replicated with other contacts for traveling longer term where there might be more stress or more flights involved? These were just kind of single point to point flights in assessment, so any thought on longer trips where you’re travelling internationally?
Hertzberg: We were talking with Boeing for a couple of years, and our Project Officer really wanted to do this in terms of fling to Japan or China, but she could never find the money within the company to fund this. And so we can’t really extend the findings beyond like a 6hour flight. I would say that they really don’t cover that, because everybody eventually has to get up. And there’s other reasons for getting up. This is not just about catching disease. If you have a circulatory condition you might be advised by your doctor to get up and not sit for hours at a time so there’s good reasons – it’s all a cost/benefit situation.
Pennington: Why do you think there is this association with flying and getting sick? Every time I fly my husband is like take vitamin C, you know, make sure like this whole idea that I’m going to get off the plane and I’m going to be ill, and I’ve bought into this whole idea that I’ going to get off the plane and be ill. And people seem to believe that, and I watch people take Clorox wipes and wipe everything down because they seem like they’re so concerned with that. Why has that become something that we – it seems like take a lot of preventative action too, if it’s really just some kind of acne bacteria that’s the most prevalent?
[Laughter]
Hertzberg: You’re in a confined space, and probably unless you’re within two seats laterally, and one row behind or in front of an infectious person, you have a relatively low probability of getting infected. And we want to – we’re biased in that we remember the flight. We don’t remember the taxi driver that was hacking up a lung between the Cincinnati airport in downtown Cincinnati when I went to the American women’s statistics and data conference.
Bailer: Apparently you do remember [laughter]. Some might not but you did.
Hertzberg: Yeah so there’s a lot of other people involved in travel where you can become infected, you know exposed to things outside your daily routine.
Bailer: You know I think about the stressors you may have, you know when you’re travelling you may not be sleeping as much, you may be in a more stressful environment, say, you’re forced to be on a podcast… [laughter] but there’s a lot of other stressors that might be part of the process of travel that might be putting you in a more compromised position. And it’s like you say, you sort of blame exposure that you think is present.
Hertzberg: Yeah exactly.
Campbell: I’m curious as to why Boeing approached you, was it because of the sort of urban legend of getting sick on planes? That they wanted to show and document that this wasn’t necessarily true? Was that their motivation?
Hertzberg: They wanted to better understand the rates and routes of transmission, and that’s actually what they called it, rates and routes of transmission so that they could design better airplane cabins. So doing things like touchless lavatories, a better circulation of air, etc..
Campbell: Especially when planes are on the tarmac and it’s claustrophobic.
Hertzberg: Yeah. We actually have a little animation that we did. We figured out where everybody was – all of our passengers and crew on each of our flights, we have an animation that we did for passenger movement and contacts, and we showed this to Boeing and they were just like bedazzled because they hadn’t really thought about it in those terms, and they were seeing things and understanding them in a new light.
Pennington: You’re listening to Stats and Stores and today we’re talking about germs on airplanes with Emory University’s Vicki Hertzberg.
Bailer: So, I’m now picturing the same study being replicated in other modes of transportation, you know? I’m thinking about my kid used to ride the Megabus back and forth from Cincinnati to Chicago, or you know taking a train or, you know, I’m just wondering how different this exposure would be, or if this has even been done with other modes of public transportation.
Hertzberg: There’s a whole field of people that are studying built environments, and there’s people that are studying subways and trains around the world. There was a big scare a couple years ago that somebody documented yersinia pestus and that’s the cause of the bubonic plague, but it turned out to be a sequencing error.
[Laughter]
Bailer: Oops.
Pennington: What advice would you give to students that want to do the kind of work that you do now? What should they be studying? What experiences should they be having to prepare themselves to do this kind of work?
Hertzberg: They really need skills in understanding the basic science underneath it. Have some understanding about how transmissions disease happens and what does all that mean, understand a little bit of basic microbiology. But I had such great training in statistics, and was able to really develop that into understanding the stochastic nature of all these interpersonal contacts that allow such transmission to take place.
Bailer: So, with working with this did you go to different mechanistic modeling? I mean we talked about movement of people within the plane, but I mean there’s certainly the idea of the exposure to that, and then the transmission and the absorption and the transition to disease status. There’s so many different places that disease could be fixed before it led to disease, was that part of framing this, or?
Hertzberg: No, we didn’t really get that far because we were just looking at the exposure, and kind of wrapped all that into the probability of infection. We didn’t really have the opportunity to get that deep into it. But I think there’s certainly that room to get through there, but you need a lot more data than we were able to collect.
Pennington: I think it’s time now, since we have a live audience to sort of throw it to the audience to see if they have questions for Vicki and I believe our producer Charles Blades is going to be running about with the mic.
Bob Starbuck: Is the air circulating in an airplane reasonably clean or are there any processes that take place on the place to try to filter the air to make it more acceptable, and is it really different than the air in a terminal? Where you’re actually exposed for quiet a bit of time as well
Hertzberg: We didn’t actually sample air on the terminal, but I will say that at least on the aircraft that we were looking at was pretty clean and it looked again like, air in office buildings or schools or those kinds of environments. It used to be that airlines really recirculated the air a lot but now they’re running them through really high-performance filters and they’re mixing in about 50% new air all the time. It actually circulates faster than many modern office buildings now. Tim Kramer: When you talked about whatever the germs and stuff being similar to a living room , is there a difference between well , that’s my living room, my body is used to those germs but it’s not used to the germs that other people are bringing in Hertzberg: Well we’re just comparing to literature, so I couldn’t really extend or extrapolate to that. but if you look at things like kitchens or hospitals, those look very different in terms of the literature on what the microbiome of those environments looks like. Wendy Martinez: So, you said you would sit by the window, can you say why that is? I mean I think I might know but can you say why you sit by the window, Hertzberg: Okay so it’s all about proximity, if we were assuming a 1-meter radius for exposure, and one meter takes you 0 if you’re in a three by three configuration, takes you out to the aisle seat but not to the aisle. And people that sit by windows tend to get up less, people that sit by windows have fewer contacts with other passengers and that’s what it’s all about is decreasing contacts, decreases your exposure you are, and your colleagues rolled it out. We are sometimes called upon to notify people who have flown on a plane that they sat next to someone who had an infectious disease, and then asked them to do certain things to ensure that they don’t get sick or spread disease further. It doesn’t happen very often just so you know but it does. So I’m really interested in how your team might be looking to further this work because it’s really relevant to public health practice and I personally would be interested in a study where you had a known infectious person on the plane, not sure how you would figure that out but
[Laughter]
But if you knew that someone was infectious and then could track who else on the plane got sick and where they were sitting or something like that or other thoughts you might have on how to continue to research this important area.
Hertzberg: That would be really tough to do because you would have to have consent of everybody you’d have to have individual identifiers. And the whole reason we were be able to do what we did was we had tremendous cooperation from an unnamed airline that is like the fourth letter in the Greek alphabet
[Laughter]
Hertzberg: But we couldn’t do anything to interfere with their workflow, okay and we couldn’t do anything in terms of asking passengers to participate. So, all we could do was observe. And I think that we would find it a very difficult cell for that fourth letter of the Greek alphabet airline to actually hep us to do something along the lines of what you’re suggesting even though it really is so incredibly important to understand.
Male Speaker: Actually my question also related to her question, so I mean actually this kind of study can be related to public health so I really think that the CDC might be interested in your research so maybe they might want to have some sort of collaboration with you so do you have any ongoing projects with them or?
Hertzberg: Well, we actually sit right across from the CDC; physically across the street. My office looks at the CDC. We have had a number of discussions with them, they were really helpful in terms of doing things like dealing with TSA and being able to get the stuff that we needed to sample with through security clearances etc. but they weren’t coming up with any funding either.
Michael O’Connelly: I’m curious what kind of experimental controls you used when collecting data on these planes.
Hertzberg: What do you mean in terms of experimental controls?
O’Connelly: So, for instance when you’re sampling bacteria or while sampling for microbiome data did you do any kind of controls to make sure that you were getting equal samples from different locations on the plane and things like that?
Hertzberg: Well we had little templates that we only sampled for a certain area for each of the surfaces that we did. We were always very careful about calibrating our air pups in terms of the volumes that we sucked in and did specific time measurements to get the same representations of time from place to place. We also had negative controls that we sent off for sequencing and we also included positive controls as well.
Bailer: So, for our general audience can you talk about what a positive control and what a negative control is? Maybe that’s something that’s new to some folks.
Hertzberg: Okay so when you’re doing microbiome a negative control would be just don’t run, take your swab okay and just stick it into the test tube that you’re going to send to the lab. Don’t swab it on anything just take it out of its package, seal it up, send it to the lab for sequencing and that kind of gives you a background for what’s there. A positive control they would take a sample that has known bacterial growth on it so you can get a relative idea.
Ben Schweitzer: I’m just curious because you said it was one airline that you worked with do you think there’s anything a specific airline could do to influence the level of germs in their plane ? like I don’t know you said Boeing was interested but if I work for an airline carrier I feel like they’re kind of the front end , I would be curious about that or if there’s any processes they do between flights that influence the level of germs in their plane or do you think that... well obviously you didn’t because you were only using one airline but is that something that you guys were interested in at all/
Hertzberg: Even if you were flying internationally for six hours from Korea to Shang Hai, or I don’t know what a six-hour flight is in Asia, but I don’t know that we would necessarily extend there.
Pennington: I think we have time for one more question if anyone else in the audience has one?
Bailer: So, now I think I know what the word is when someone sneezes on the plane
Nathan Drew: Hi, Nathan Drew. Were you able to gain any insight into the occupational hazards, so the airline crew? Are they maybe more susceptible since they tend to see longer exposures?
Hertzberg: Yes the airline crew are more susceptible if one of them shows up sick, okay? because they spend a lot of time with each other but as far as passengers, if they’re exposed to an infectious passenger they’re not as likely to get sick as the people that are immediately seated around them. We had found that we had also done a study in emergency rooms and looked at contacts there and it’s the emergency room staff the practitioners, the nurses, care providers the administrative clerks there’s a tremendous social pressure in epidemics to show up no matter what and to keep working no matter what and that means that people show up or stay when they are sick and if they stay when they are sick they are spreading it to each other and to the patients. Whereas they tend to think that the patient is the enemy. The patient is the one that they’re going to get it from, and we found that isn’t true either.
Bailer: That’s fascinating,
Pennington: Well Vicki thank you so much for being here, that’s all the time that we have for this episode,
Hertzberg: Well thank you very much and love and honor.
[Applause]
Pennington: Stats and Stories is a partnership between Miami University’s Department of Statistics and Media, Journalism and Film, and the American Statistical Association. You can follow us on Twitter or Apple podcasts or other places where you can find podcasts. If you’d like to share your thoughts on the program send your emails to statsandstories@miamioh.edu or check us out at Statsandstories.net, and be sure to listen for future editions of Stats and Stories, where we explore the statistics behind the stories and the stories behind the statistics.
[Applause]