'Tis The Season For Cold And Flu Both bring wintertime suffering, but how different is the common cold from influenza, scientifically speaking? Ira Flatow talks with cold and flu experts about how these viruses are transmitted, how best to dodge them, and why hand sanitizer may not be of much help.
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'Tis The Season For Cold And Flu

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'Tis The Season For Cold And Flu

'Tis The Season For Cold And Flu

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Now that the cold and flu season is here, I find myself making liberal use of that hand cleaner, don't you? You push that little pump down on your hands or you squeeze the bottle, you know, with that alcohol-based gel. It's supposed to kill all those bad germs, isn't it? In fact, the one of the bottles says it kills 99.9 percent of the germs. Well, not according to the latest tests. Don't count on hand sanitizer to ward off cold viruses. Really. Don't do it. We're going to tell you why because we're going to talk about just how cold and flu viruses are spread, what does work, what does not work. And there are some really surprising answers that have come out of some recent studies. And I'm going to call in my cold and flu experts - Peter Palese is a flu expert. He's a professor and chair of the microbiology department at Mount Sinai School of Medicine here in New York. Welcome to Science Friday.

Dr. PETER PALESE (Professor and Chair, Microbiology, Mount Sinai School of Medicine, New York): Good afternoon.

FLATOW: Good afternoon. J. Owen Hendley is our common cold expert. He's a professor of pediatrics at the University of Virginia School of Medicine, and he has been studying the common cold for over 30 years. Welcome to Science Friday, Dr. Hendley.

Dr. J. OWEN HENDLEY (Professor, Pediatrics, University of Virginia School of Medicine, Charlottesville, Virginia): Seem like I would have figured it out by now, doesn't it?

(Soundbite of laughter)

FLATOW: Why don't we begin with you. Tell us why - about hand sanitizers. Why won't they protect us from getting a cold?

Dr. HENDLEY: Well, if you accept the notion that most of the time we give ourselves a cold because we get virus on our hands and then we stick it in our nose or stick it in our eye and that's the point at which infection occurs, the hand sanitizers - the problem with them is that rhinovirus, which is responsible for at least half of colds in adults and children - rhinovirus kind of likes alcohol, which is the active ingredient in all the hand sanitizers that are available.

FLATOW: It's sort of laughing at you then when you pump out?

Dr. HENDLEY: Well, it kind of likes it. And there's actually been some field work, not done by me but done by Don Goldman's group at Boston - in Boston, where they found that active use of hand sanitizers in the homes apparently had no effect on secondary illnesses, that is illnesses acquired after somebody else brought the virus home. So, I think that there's a cheaper way actually - although hand sanitizers aren't very expensive. There's a cheaper way, which is simply washing your hands before you pick your nose or rub your eyes.

FLATOW: Or just washing your hands in general, anytime during the day. And how - is there a method - a right way and the wrong way to wash your hands?

Dr. HENDLEY: I don't know about it if there is. I usually use a little bit of soap, simply because it makes me rub my hands together to get the soap off of there but...

FLATOW: I mean, do you have to wash them for 30 seconds, a minute?

Dr. HENDLEY: No. I don't think so. In stuff we've done in the lab, it's quite honestly simply rinsing your hands and rubbing your fingers together, you can wash the virus away. And it goes out into the river, of course, but it doesn't cause any problem there.

FLATOW: Now, you've studied other methods of killing cold viruses, have you not?

Dr. HENDLEY: Well, we're looking at doing something about surfaces, but I say my advice always is wash your hands. That is the simplest way to do it. And I'm not very excited about hand sanitizers. My sense is that it may be it'll smear the virus around. It should be said that the alcohol will kill influenza virus and it'll kill a whole bunch, you know, a bunch of other viruses that are sensitive to it, but rhinovirus is one that's not.

FLATOW: Dr. Palese, you agree?

Dr. PALESE: Yes, absolutely. I mean, I think, even though influenza, in contrast to common cold, is probably more likely to be transmitted through the air as an aerosol, none of us, even us influenza virologists, are against washing hands.

(Soundbite of laughter)

FLATOW: Well, I understand, Dr. Hendley, that you're working with acids, common acids like citric acid found in lemons, proving effective against the cold virus?

Dr. HENDLEY: Yeah, and I can't tell you that rubbing your hands with a lemon is going to make any difference, but the reason - well, rhinoviruses are differentiated from another group of similar viruses by virtue of the fact they're sensitive to acid treatment. It, you know, chews the virus up or inactivates it. So, the possibility that by addition of an acid, which you could tolerate - which, certainly citric acid you could tolerate - whether addition of an acid you could tolerate to the alcohol would be helpful is currently under investigation, as a matter of fact.

FLATOW: We're talking about spreading cold and flu viruses this hour on Science Friday from NPR News. Now this raises - let me just give out our number, 1-800-989-8255. 1-800-989-TALK. Also, if you'd like to Twitter us, we have a Twitter address, that's @ - the "at" sign - scifri, S-C-I-F-R-I. And always in Second Life, you can find Science Friday island.

You know, the fact that the cold viruses are spread by hand raises an interesting paradox - or problem for me. I mean, for me, the place where most people are touching things would be in the supermarket, you know? With the fruits, the squeezing melons and lemons and all things like that - aren't we swapping all those cold viruses right there?

Dr. HENDLEY: Maybe.

(Soundbite of laughter)

Dr. HENDLEY: The place that we have focused on is the home, actually, in work we've just finished. But we had previously, a year or so ago, did a study of adults who had colds and we put them in a hotel room overnight to see - and then the following day, we went in and asked them to point out 10 places that they had touched in their overnight stay. And then we sampled those and tested for the presence of virus - well, really, for the presence of the RNA of the virus. And not surprisingly found something - a third to 40 percent of the sites that they pointed out to us had evidence of virus having been there. And it was the usual sites that you can imagine - the light switch and the telephone and the TV remote and the faucet handle in the bathroom, that sort of thing.

One of the most interesting negative findings was that we did not find virus on the toilet handle in any one of the 10 samples that we tested. So, I don't know, this allows me to speculate all kinds of way about people's behavior toward the toilet handle, but colds spread best in the home. I think that's probably fair. And perhaps the most impressive evidence against airborne spread is that, although you and your coworker may very well have a cold at the same time, from work we did in an insurance company some years ago, the type - the serotype, or the virus that you have and the virus that your coworker has, are probably not the same. But if you go into the home, you can find each worker's virus circulating in people in the home.

FLATOW: There are very many cold viruses, are there not?

Dr. HENDLEY: (Laughing) Oh, yeah.

FLATOW: A couple of hundred?

Dr. HENDLEY: Well, there's - there're 100 numbered rhinoviruses and there are other viruses that can cause colds, but at least a hundred. And with sensitive nucleic acid detection techniques, it's pretty clear that there's some more that we haven't been able to grow in cell cultures so far. So, it - apparently, you become immune to virus number one when you get infected with it, but then you got 99 more to go before you get through them all, so it's a little bit discouraging.

FLATOW: That's why you see so many kids, young kids, with so many colds all the time. They haven't gotten that immunity yet.

Dr. HENDLEY: Well, that and maybe poor hygiene (Laughing) is part of the game. I don't know.

(Soundbite of laughter)

FLATOW: Dr. Palese, is that - flu is not spread the same way, is it?

Dr. PALESE: They are - we should say that common cold is caused by a virus, and influenza is also caused by a virus. But there are really differences among these two families of viruses, those which cause the common cold and those which called influenza proper. And with influenza, which is very seasonal - in other words, we only really see it from maybe December to February, March. So, it's highly seasonal during the winter months, in contrast to common cold viruses, which can be observed or can be caught throughout the year. So, there are differences between these viruses, and one of them is also that for influenza - again, I'm not against washing hands, but it's probably more likely to be transmitted through the air as an aerosol, that there is airborne transmission by being in the same room, by being in the same elevator, et cetera.

FLATOW: OK, Dr. Palese, let me stop you there because we have to take a break. We'll come back and talk lots more about cold and flu viruses. Stay with us. We'll be right back.

(Soundbite of Talk of the Nation theme)

FLATOW: I'm Ira Flatow. This is Science Friday from NPR News.

(Soundbite of music)

FLATOW: You're listening to Talk of the Nation, Science Friday. I'm Ira Flatow. We're talking this hour about cold and flu. My guests are Peter Palese, he's a professor and chair of the microbiology department at Mount Sinai School of Medicine, right here in New York. J. Owen Hendley is a professor of pediatrics at the University of Virginia School of Medicine. Our number, 1-800-989-8255 is our phone number. Also taking calls at - Twittering, @scifri is our Twitter and also on Second Life, you can go to Second Life island. Let me go - before we take a phone call or two, let me ask you, Dr. Palese, how do environmental or air conditioning sorts of things affect the transmission of the flu?

Dr. PALESE: So, transmission of influenza cannot be studied very easily with patients because there are ethical reasons to - not to allow those kinds of studies. It used to be that we had medical students and asked them to stay in a hotel room and then they get infected and then we were able to study transmission. At this point, we really have to go into animal experiments and mice - the laboratory mice are sort of the animal of choice for influenza. But it turns out that influenza is not transmitted very easily among mice. And so we had to develop a new animal model and that is guinea pigs. And it showed us that influenza is really transmitted much better at cold temperature and at low relative humidity, as compared to high temperature.

FLATOW: So, high temperature would be what, above 80 degrees Fahrenheit?

Dr. PALESE: Above 80 degrees. So we found - and this is sort of a finding which probably is interesting for us - at 81 degrees, we were not able to find - to observe transmission from one guinea pig to the other. And that would suggest that if we could warm - or if we would warm our rooms and buildings to above 81 degrees, we would avoid influenza transmission. However, we would buy a lot of other problems. First, the cost of heating, the very uncomfortable high temperature and high humidity, which would lower the transmission, would also allow growing of bacteria. So, this is not a practical solution, going above 81 degree Fahrenheit.

FLATOW: What about if you limit it to, like, hospital waiting rooms or doctor - patients' offices where you know that these people with the flu are sitting?

Dr. PALESE: I believe that this is still unpractical, even in a sort of high-risk environment, as a waiting room for a physician. I think this still would not be good. However, what it tells us scientifically is that, yes, the virus is much less stable at the higher temperature. And the other side of the coin is that the virus is more stable at low temperature if you go down to 40 degrees and low relative humidity. And this stability of the virus under those temperature and humidity conditions makes the virus much easier to be transmitted.

FLATOW: That's why we get it in the colder weather?

Dr. PALESE: And that is most likely the reason we get it during colder temperatures, and also it turns out that there is some change in the respiratory tract, the mucus is more viscous, so we are not able to clear viruses and probably bacteria as rapidly as at higher temperature.

FLATOW: 1-800-989-8255. Daniel in Rice Lake, Wisconsin. Hi, Daniel.

DANIEL (Caller): Hello. I heard on a news report that the influenza virus could remain viable or able to infect cells and replicate even up to 17 days on paper currency. What advice have you for people who handle currency during flu season?

Dr. PALESE: OK. I'm very much aware of this paper. This is actually Swiss money though, this is a paper when they used Swiss money and they were able to show that, indeed, under those circumstances, virus was stable. I'm sort of somewhat - firstly, I was told that the Swiss currency is very different paper, very different material from our currencies. And I'm somewhat - I mean, I'm not refusing to believe it, but I think it is probably less likely that this is a major way of transmitting influenza.

FLATOW: But how long, Dr. Hendley, might cold virus survive on a dollar or paper currency?

Dr. HENDLEY: (Laughing) Well, I don't know about paper currency. It certainly can survive on hard surfaces for anywhere up to four days. Although in kind of transmission stuff that we've done, it looks like it's viable virus that's transmitted for 24 hours and then probably it's less likely to be transmitted after that. So, I don't know about dollars. (Laughing) I can't imagine studying that.

FLATOW: There aren't that many dollars around.

Dr. HENDLEY: Yeah, that's right.

FLATOW: Study dollars. But you - there is a famous study about poker players, is there not?

Dr. HENDLEY: Yeah. And this study - this was done at the University of Wisconsin. They had people who were artificially inoculated with virus and then they played poker with chips and cards and stuff, which would be non-porous surfaces. Then, they took the chips and the poker - and the cards into another room where there were susceptible volunteers and got them to play with them, and I find surprising, but anyway, they found no transmission by way of the poker chips and the cards that went there. This is - well, that's what they found.

FLATOW: So, no poker chips and no toilet handles so far?

(Soundbite of laughter)

Dr. HENDLEY: Yeah, right. (Laughing) I don't know. Yeah.

FLATOW: (Laughing) It's a real mystery going on.

Dr. HENDLEY: Yeah, it is. And I say that the group at Wisconsin was - they were strong believers in the importance of aerosol spread, so spread through the air, although their work was kind of a mixed bag of things. So, although we focused on the hand/self-inoculation route, the possibility that it spreads through the air always is there. And as Dr. Palese's told us that - I was going to ask him, as a matter of fact, his speculation as to why influenza was so remarkably seasonal. And I think he's already given the answer, which is it's presumably that the virus survives in the air better when it's cold than it does when it's warm. Do I have that right, Dr. Palese?

Dr. PALESE: Yes. And also, we found that the virus is - in the animal, cleared - it takes much longer to clear the virus in animals, which we have put for a whole week at 40 degree Fahrenheit. So, there appears to be some change in the upper respiratory tract as well...

Dr. HENDLEY: I see.

Dr. PALESE: ...when people are out in the - I should emphasize these are animal experiments, but we really like - would like to extrapolate this with a human patient as well.

Dr. HENDLEY: Yeah.

FLATOW: Dr. Hendley, with your ideas about, you know, acid and lemon juice and things not allowing the survival of the viruses - I would think that somebody should come up with a product, you know. Stick this stuff in a bottle.

Dr. HENDLEY: (Laughing) Well, it would seem so to me, too, as a matter of fact. You hear where my emphasis is, though. What's cheap and available is hand washing.

FLATOW: Lemon juice is pretty cheap.

Dr. HENDLEY: (Laughing) Yeah, OK.

(Soundbite of laughter)

Dr. HENDLEY: It needs to be studied, Ira. Come on, now.

FLATOW: Hey, I'm just throwing it out there. I don't make these things. I just create the buzz so we can talk about them and get...

Dr. HENDLEY: Yeah.

FLATOW: ...we get the wheels of industry moving and creativity going.

Dr. HENDLEY: There you go, there you go.

FLATOW: Speaking of creativity, Susan in Ridley Park, Pennsylvania is on the phone. Hi, Susan.

SUSAN (Caller): Hello, there.

FLATOW: Hi, there.

SUSAN: Happy New Year to everyone.

FLATOW: Thank you. Happy New Year to you.

SUSAN: I am calling because I use a lot of - can your doctor hear me?


Dr. HENDLEY: Yeah.

SUSAN: OK. I am calling because I use a lot of public transit and then I'm in a lot of public places - hospitals, stores. And believe it or not, a lot of times, I can't even get hot water or soap in a bathroom. And I'm just wondering, what can I do if that's the way and I want to clean my hands, say, before I eat or need to drink something? And like I said, I'm out in all these public places.

FLATOW: I'm not going to tell her to squeeze lemon juice on her hands.

Dr. HENDLEY: No. I was going to say Ira knows the answer.

FLATOW: No, I'm not going to say do that.

Dr. HENDLEY: (Laughing)

SUSAN: That would burn. (Laughing)

(Soundbite of laughter)

SUSAN: Lemon juice, I think that would burn, wouldn't it?

FLATOW: Dr. Hendley, any suggestions for this lady.

SUSAN: Yeah. Public transit and the bathrooms I go into...

Dr. HENDLEY: Yeah.

SUSAN: Believe it or not, have no...

FLATOW: What if you wore - what if she wore gloves or, you know, surgical gloves or something like that?

(Soundbite of laughter)

FLATOW: You know, I'm serious. She's concerned about this. And then she could just throw out a pair and put on another one.

Dr. HENDLEY: Yeah and people wouldn't - would avoid you a little bit, too, I think, if you're walking around with your gloves on. I know the problem, having been trapped in bus station bathrooms before. And getting out of the bathroom without picking up something that was left on the handle and stuff like that would be quite difficult. I don't have a reasonable answer, quite honestly. And when Ira's lemon juice gets patented...

(Soundbite of laughter)

Dr. HENDLEY: ...you can do that.

SUSAN: Does it help then, to use, like, those WetOnes, they're called, or any kind of hand sanitizer when you don't have your soap and water?

Dr. HENDLEY: Well, wiping is - also works to remove virus. That's true. Whether that's enough, I don't know, and it seems right because your hands feel a lot better. But I'm sorry, it's not been studied. But I - if I was really strapped, I'll probably use WetOnes and wipe - try to wipe the virus off my fingers.

FLATOW: But didn't you tell us that alcohol does not kill the cold virus?

Dr. HENDLEY: Well, but now it's adding in here, Ira, is wiping. So, if you're doing - if you're putting - squirting something on your hands, which is the way hand sanitizers are used, and then it stays on there, you don't wipe it off. Whereas if you wipe it on - I can imagine even wiping it on a wet cloth as a means of removing the virus, certainly from surfaces you can remove virus - remove rhinovirus very easily with wiping.

FLATOW: OK, Susan?

SUSAN: ...WetOne, you mean?


SUSAN: Then I'm wiping my hands.

FLATOW: Yeah. Wiping will help. Thank - have a happy holiday season. It's almost over. Take care.

SUSAN: Thanks a lot.

FLATOW: Bye-bye. You know, I was on a cruise ship recently and I saw something I had never seen before, and that was on the exit to the bathrooms...

Dr. HENDLEY: Right.

FLATOW: ...they had a sign that says please use a towel when holding the handle of the door.

Dr. HENDLEY: There you go.

FLATOW: I had never - you know, cruise ships have had that - those problems with spreading of bacteria.

Dr. HENDLEY: Oh, well, the big problem - or one of the big problems on cruise ships is Norovirus, which causes gastroenteritis. And they'd be very happy for you not to transmit - put that on the handle and then have somebody come along and pick it up on the handle.

FLATOW: Dr. Palese, what is the best way to prevent getting the flu?

Dr. PALESE: For influenza, since the majority of transmission is through the air, we can probably not do much in terms - yes, we can avoid certain rooms, but just not touching something is not so easy because we have to keep breathing. At least, some of us want to do that. So the best, probably, is still vaccination. This is really a way of avoiding influenza. It's not a perfect vaccine, but it is really probably the best way of preventing influenza. Unfortunately, it is an under-utilized or under-used vaccination. And I really feel that people should consider taking the vaccine and, by virtue of doing that, have a good chance not getting influenza. It is not 100 percent, but it's still a very, very good way of preventing the disease.

FLATOW: This is Science Friday on NPR News. I'm Ira Flatow, talking about cold prevention and flu prevention. And we got a tweet on Twitter here from Ulysses2112 who says, can cats and dogs catch colds? And I'll expand that to include the flu. Can your dog or cat get the flu?

Dr. HENDLEY: I can speak for rhinoviruses. And the cats and dogs cannot get infected with rhinovirus. Humans and non-human primates are the only ones that are susceptible to the virus. Now, on the other hand, Dr. Palese's going to tell us about flu.

Dr. PALESE: Yeah. Cats and dogs - I mean, really, pets do not get influenza from humans. So, this is not a way of transmitting the disease or getting the disease. There are some very unusual influenza viruses which have been shown to infect cats, tigers, leopards. But in general, cats and dogs do not get our human influenza and therefore, also cannot give it back to us. So, they are really, I think, very safe. There are other animals, as we know - for example birds, pigs, horses - which can get influenza, but not cats and dogs.

FLATOW: Why have we not heard anything about the bird flu for the last year or so?

Dr. PALESE: Yes. The avian influenza, the bird flu, is - I always say, is very bad if you're a chicken. So, this is a very highly lethal, highly pathogenic virus, where up to 70 percent, 80 percent of a flock of chicken, of turkeys can die. So, it's a very virulent virus. But in humans, only under certain circumstances, probably high doses can cause disease or can cause death. In general, this virus is not transmitted from human to human and I think at this particular point, we are really safe from any outbreak of avian influenza. It is really a bad disease if you're a chicken. But for humans, fortunately, this is not yet a major danger.

Dr. HENDLEY: That's well said, Dr. Palese.

(Soundbite of laughter)

Dr. HENDLEY: We've been waiting for the bird flu to come take us over and it hadn't done it, so...

FLATOW: Yeah. Well, Dr. Hendley, let me ask you - I got about a minute left. I'll give you the blank-check question. You've been studying colds for 30 years. What has baffled you most? What has surprised you the most?

Dr. HENDLEY: OK. What's baffled me the most is, even if you kill the virus a little bit, you really don't alter the course of the disease, probably because the inflammatory response, which is what is causing the symptoms that you have, has already begun, and just killing the virus then doesn't make it so you feel better immediately. That's a little troublesome to me.

FLATOW: All right. Well, thank you very much for taking time to talk with us, gentlemen, and have a great - Happy New Year.

Dr. HENDLEY: Thank you.

FLATOW: You're welcome.

Dr. PALESE: Thank you.

FLATOW: Peter Palese is a professor and chair of the microbiology department at Mount Sinai School of Medicine here in New York. J. Owen Hendley is a professor of pediatrics at the University of Virginia School of Medicine.

(Soundbite of acknowledgments)

FLATOW: If you have questions, write to us at Science Friday. Surf over to our Web site. You can leave us email there. Also, we're podcasting and blogging at sciencefriday.com. If you missed any of the references we talked about today, just surf on over there to sciencefriday.com. Also, we have videos up there. We still have last week's pick of the week - video pick of the week that Flora had picked out for you. Great stuff to look at. And also, you can send us your own videos. We're always interested in seeing what you have to offer. I'm Ira Flatow in New York.

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