Tracking The Spread Of A Nasty Virus

When members of a travel soccer team in Oregon fell ill last year, the details of how the disease spread through the team were mysterious. Kimberly Repp, an epidemiologist in Washington County, Oregon, describes the medical detective work that led epidemiologists through the chain of transmission of the norovirus.

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IRA FLATOW, HOST:

This is SCIENCE FRIDAY. I'm Ira Flatow.

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FLATOW: Now a medical mystery...

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FLATOW: ...about a stomach virus you don't want to get. Flora Lichtman is here with the story. Hope you already had lunch. Flora?

FLORA LICHTMAN, BYLINE: Ira, this story is a little disgusting, but also scientifically significant. Here's the setup: A soccer team goes on the road to play a tournament. One member gets violently ill. She leaves the hotel, along with a chaperone she was staying with, before coming into any direct contact with the other players. Yet a few days later, seven other players get sick with the same virus. The mystery is: How did the virus spread without the sick girl? Well, Dr. Kimberly Repp cracked the case. Dr. Repp is an epidemiologist in Washington County, Oregon and one of the authors of a paper in the Journal of Infectious Diseases describing the outbreak. Welcome to SCIENCE FRIDAY, Dr. Repp.

DR. KIMBERLY REPP: Thank you. It's an honor to be here.

FLATOW: Doctor, did we miss anything important in that setup to this mystery?

REPP: No, that was beautiful. The work was done in conjunction with Dr. Bill Keene at the Oregon Health Authority, so we worked together on it.

LICHTMAN: OK. So tell us how you solved it. What's the answer to this mystery?

REPP: Well, unfortunately the chaperone had stored a bag of food in the bathroom where the first girl became ill, and the girl was ill for about six hours with vomiting and diarrhea. And completely unknown to her teammates, one of the other teammates, after she had already left, walked into the room, grabbed the bag with the food in it, and took it into the team room, and it was shared with the team. And that's how we believe they became ill.

LICHTMAN: Oh, the snacks.

REPP: Yes, yes.

LICHTMAN: It seems so innocent.

REPP: It does. You know, just trying to help with cookies and grapes and packaged chips and great team snacks, but unfortunately had a little bug on it.

LICHTMAN: And what bug are we talking about?

REPP: We're talking about norovirus.

LICHTMAN: And what is norovirus?

REPP: Norovirus is commonly referred to as stomach flu. It causes acute gastroenteritis. It's very contagious. It spreads easily and the main method - the main thing we want to try and do is prevent secondary spread of infection.

LICHTMAN: So I guess the question is how did it actually get on that bag.

REPP: Well, when people become violently ill, the virus is aerosolized, and it lands, anywhere. So when you're in an enclosed space like a bathroom, like most of us are when we're ill, and the virus goes up in the air, it lands on the countertops, toothbrush, everywhere. And then if we don't clean those surfaces in that environment, we can transmit disease.

LICHTMAN: Well, how long can it stay on your toothbrush or your light switch and then be - still be contagious?

REPP: We have - there are varying reports on that, but it's estimated that at least two weeks the virus can stay alive on a normal surface.

LICHTMAN: Two weeks?

REPP: Yeah.

LICHTMAN: Wow. That makes you think twice about using a public restroom - or me, anyway.

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REPP: Well, usually most people don't become ill in a public restroom, right, so it's probably not as great a risk. But if someone is ill, we do know now that we should certainly be cleaning those environments with a proper bleach solution, 10-to-1 bleach solution.

LICHTMAN: Is it something special about norovirus so that it can survive so long on, you know, outside of the human body or outside of a host?

REPP: It's a beautiful pathogen, and it knows how to spread itself very well by aerosolizing. That's why the onset is so extreme, and that's why a lot of people unfortunately pass away from the virus, because they can't survive the onset. But the virus itself is a beautifully designed pathogen, and it's the most common foodborne illness.

LICHTMAN: What does it do when it's not in the body? Does it sort of hibernate? Do we know?

REPP: I don't think we have a lot of information on that because, quite frankly, we can't get it to grow in the lab.

LICHTMAN: Really?

REPP: Yes.

LICHTMAN: Why is that?

REPP: Well, we're working on it. Everybody - there are lots of very, very talented scientists working on that, but it's a special little pathogen.

LICHTMAN: And how much do you need to be exposed? I mean in the case of the outbreak you described, it seems like you didn't need much. I mean, these girls didn't much to get sick.

REPP: Well, the norovirus actually has the lowest infectious dose of any virus known. It only takes 18 viral particles to get an infection, which is practically nothing when you think there are over a billion of the viruses in one gram of feces. So...

LICHTMAN: Oh, wow.

REPP: Yeah.

LICHTMAN: Only 18.

REPP: Only 18, yup.

LICHTMAN: Wow. And they can be on that - on the counter for two weeks, and you can become infected. And then do you have to put your hands in your mouth or something? Is there a - do they need a special way in?

REPP: Yes. Yes, of course, the virus needs to gain entry into your body. But with most humans, touching their face and their eyes and rubbing their nose as often as we do, it's - that's pretty trivial.

LICHTMAN: So for this study, did we know that this could happen? Did we suspect it?

REPP: Oh, absolutely. Everyone has suspected this for years and years and years. We've known that the norovirus can be aerosolized. That's been known. And we have been able to isolate norovirus from door handles and keyboards and various outbreaks. This is kind of just filling in the missing link between: Is this actually possible to not have any contact with a sick person and still get sick just from touching an inanimate object?

LICHTMAN: Hmm. And it is.

REPP: It is. Yup.

LICHTMAN: It is. So tell me a little bit about how you actually did this study. It sounds like there was a lot of detective work involved.

REPP: Yeah. We had a good time with this. We received a call from the State of Washington Health Department, informing us that some Oregonians were sick, and it met the definitions for - the criteria for an outbreak, so we conducted a full investigation. Over the course of about three days, we interviewed all the healthy and sick people on the soccer team, all the chaperones. Washington State helped interview other teams that were at the soccer tournament to see how big it was.

There was a lot of work from a lot of people on this. And from interviewing the players, we were able to determine that these pre-packaged cookies were associated with illness. And from determining it was the cookies and what the cookies were in, we were able to put the piece together. But it took three interviews with the teammate that - excuse me, with the team players to actually get out the information that somebody had gone into the bathroom and retrieved the bag.

LICHTMAN: I bet they felt bad about that.

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REPP: Oh, it was horrible. I could - I was speaking to the person, and she started putting it together. She's like, oh, oh, no. It's the bag, isn't it? It's my fault. I'm like, no, no, no. We're not - we don't know anything yet. We're just trying to put this together. And, oh, yeah, you could see her connecting dots, and she was upset, of course.

LICHTMAN: Do you take physical evidence, too? Do you swab things and stuff like that?

REPP: The only physical evidence in this case besides the stool specimens provided by the players was the actual bag involved in the outbreak. And I retrieved that two weeks after the outbreak, and our wonderful lab quickly ran it and was able to isolate a virus from the bag. But we were unable to determine if it was infectious or not.

LICHTMAN: So is this what epidemiology is all about? Is it really like a sort of detective work-type of field?

REPP: Absolutely. I think this is the really, really, really fun part of epidemiology, and this is what makes us public health people love our jobs.

LICHTMAN: Hmm. Yeah. I mean, it really is mystery work. If you want to get in on this conversation, our number is 1-800-989-TALK. 1-800-989-TALK. So is there something else about - are there other viruses like norovirus in their robustness or their ability to - could you find other things on the light switch, I guess?

REPP: I am sure you could. I'm not necessarily familiar with any other viruses that can do it to this extent. This is the method of transmission for this bug. It likes to be airborne. It likes to land, and that's basically - it's pretty unique in that way. There are lots of other food-borne illnesses that are associated with bacteria, but not necessarily a lot of other viruses.

LICHTMAN: Our number is 1-800-989-8255. So when you're not working on norovirus, what do you do, usually?

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REPP: Obsessively clean my house.

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REPP: No. I'm a big dog person, so I like to read and hang out with my family and be with my dog.

LICHTMAN: So what do you suggest for people who are - hear this - hear about this outbreak, and they're, like, you know, grossed out and worried? What's a suggestion?

REPP: Well, the first - number one take-home message is don't ever store food in your bathroom. I know that goes without saying, but it probably just - you know, sometimes we don't think about it, and we might bring something into the bathroom and leave it there. But just don't do that. And, secondly, if someone has become ill in your household, if possible, isolate them to one bathroom, or keep all the sick people in one bathroom. That will also help stop secondary transmission. And, third, clean it properly. You know, don't just wipe down the toilet like we all do. Get out the bleach solution and wipe down the countertops. Throw away things that you can replace easily, and then you'll be OK.

LICHTMAN: Has this made you an obsessive cleaner? I mean, were you serious about that?

REPP: I have a PhD in microbiology, which requires obsessive-compulsive disorder to actually get that, I think.

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REPP: So, no, this didn't make me any worse.

LICHTMAN: Are there other viruses that you study?

REPP: No. I am - well, actually, I shouldn't say that. We just had another paper in the Journal of Infectious Diseases this month for the human papillomavirus and its association with condom use in men in an international cohort study.

LICHTMAN: Dr. Repp, thank you so much for taking time to be with us. This was a fascinating study. I have to say, of all the scientific papers I've read, none of them have read quite so much like a detective case.

REPP: Thank you.

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LICHTMAN: Dr. Kimberly Repp is an epidemiologist for Washington County in Oregon and the co-author of this paper in the Journal of Infectious Diseases, "A Point-Source Norovirus Outbreak Caused by Exposure to Fomites."

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