Coronavirus: Sanitizing, According To Science

IRA FLATOW: This is Science Friday. I’m Ira Flatow. The new coronavirus, responsible for more than 5,000 deaths now around the world this winter, is in the US. The numbers are growing. Maybe you’ve already canceled travel plans because of that. Maybe you were looking forward to March Madness, baseball, hockey, or golf games that will no longer happen. Maybe you’ve gotten a cold that you’re really hoping is just a cold, but you can’t get a test to prove it’s just a cold.

And OK, maybe some of you living in a cave are not distressed at all. Well, whatever your mind state is right now, I’m sure you’ve heard two mantras to ward off the disease. One, stay away from crowds, and now say this with me now, wash your hands with soap, and for 20 seconds. Hand sanitation has also been a common theme in the questions we’re receiving from our listeners.

GARY: I’d like to know if hand sanitizer will kill coronavirus on my hands. And I’m also wondering if anybody has good tips on how to keep my hands away from my face. That’s so hard.

EVAN: I was wondering whether hand sanitizers are effective against the coronavirus, or is old-fashioned soap and water a bit a solution.

IRA FLATOW: Hm. Good questions. Asking those are Gary and Evan from Australia on our Science Friday VoxPop app. So as we are being urged to practice good hygiene, how do we even know that this works? Yes, there is a science to how soap breaks down viruses, and there is a reason it is better than sanitizer. Here to talk more about killing a virus and how do you do that, and why it matters for everyone to keep clean is Dr. Benhur Lee, professor and chair of microbiology at Mount Sinai’s Icahn School of Medicine here in New York. Welcome, Dr. Lee.

BENHUR LEE: Thank you, Ira.

IRA FLATOW: And Dr. Saskia Popescu, senior infection prevention epidemiologist for Hope Health in Phoenix, Arizona. Welcome back to Science Friday.

SASKIA POPESCU: Thanks so much.

IRA FLATOW: And we’re taking your coronavirus hygiene questions. Our number, 844-724-8255, 844-SCI-TALK, or tweet us @scifri. Let me let me ask you first, Dr. Lee, everyone is talking about handwashing. I’m singing Twinkle, Twinkle, Little Star in my sleep now, because that’s how long I use to scrub my hands. Why is it so effective about a coronavirus? What’s going on in the soap and the water and the viral particles?

BENHUR LEE: I’ll be happy to answer that. I just want to correct the fact that I am not chair, [INAUDIBLE] chair, just so that I don’t get fired.

IRA FLATOW: Well, you might be chair after this is over.

BENHUR LEE: And in any case, yes, so soap first, right? So soap is important, one, because it’s a surfactant. It has what we call– all detergents are amphipathic molecules. They have a polar end, meaning likes water, and a non-polar end, a hydrophobic end that does not like water.

And so when you have two ends of a molecule, all the parts that are hydrophobic will cluster in the center, as you may, and all the parts that like water surround the parts. So you get a micelle. And these micelles will basically surround and dissolve membranes. And coronavirus has a lipid membrane. Bacteria has a lipid membrane.

IRA FLATOW: It’s a fatty thing.

BENHUR LEE: There’s a fatty thing. And so–

IRA FLATOW: And because soap likes fat–

BENHUR LEE: Yes.

IRA FLATOW: –it takes fat–

BENHUR LEE: [INAUDIBLE]

IRA FLATOW: –off your hands, grease, right?

BENHUR LEE: Yes, exactly. And the way it does so is exactly what I just said, because, you know, it’s kind of a fat itself, and so it dissolves the fat. And with water, it washes it away. And so that’s how you get grime and dirt and stuff like that, too.

IRA FLATOW: One part loves the fat, one part loves the water.

BENHUR LEE: Yeah, exactly.

IRA FLATOW: And so they stick it together and go down the drain.

BENHUR LEE: Yeah. That’s why you do this for a living, Ira.

IRA FLATOW: I’ve talked about this for so many years. I mean, it’s really fascinating to me the chemistry of what it is. Now, the fact that you need to do it for 20 seconds, is that important? Why is that important?

BENHUR LEE: You know, not all things– I bet there are studies to show how long you wash it. And there are. There are studies even with hand sanitizers where you wash it for 10 seconds or 30 seconds, and then you can just put your, you know, culture whatever remains. And in science, we call that bacterial load because that’s easy to culture out [INAUDIBLE].

And the longer you wash it, the greater decrease. And in this infectious disease, we don’t care about decreasing things by 50%. And we care about decreasing it by 10-fold, 100-fold. And that’s important. That’s why 20 seconds is kind of a sweet spot. Also an abundance of caution to make sure people don’t just rinse it for, you know, yeah.

IRA FLATOW: Let me ask Dr. Popescu, what other things work besides soap and water?

SASKIA POPESCU: You can use alcohol-based hand sanitizer, but the key is that it needs to be at least 60% alcohol. And we have to acknowledge that it’s going to reduce the number of microbes on your hand, it’s not going to eliminate all of them. So I think the key piece, and you know, everybody’s buying up hand sanitizer right now, is definitely use that, but you really need to wash your hands every few times that you use hand sanitizer, because that mechanical motion of soap and water for 20 to 30 seconds, that’s what’s going to get rid of a lot of that bio burden and that grime that microbes like to grow on.

IRA FLATOW: So you need that friction of actually rubbing your hands together with the soap and water.

SASKIA POPESCU: Exactly. Yeah.

IRA FLATOW: We just heard how soap works. How does alcohol work to kill the virus?

SASKIA POPESCU: Well, alcohol really helps disrupt the cellular membrane. I’m sure Dr. Lee can speak more to that for viruses. But you know, as long as it’s 60% alcohol, that’s the big piece. So it helps break down that outer part of the organism.

IRA FLATOW: Dr. Lee?

BENHUR LEE: Yes, and I don’t want to insult the listeners, but I have to make sure that, when we say alcohol, we don’t mean vodka and spirits.

SASKIA POPESCU: Yes.

BENHUR LEE: Yes. It’s– you know–

IRA FLATOW: One kind specifically of alcohol?

BENHUR LEE: No, there’s isopropyl. So this is ethanol. I’m showing [INAUDIBLE]

IRA FLATOW: You’re holding it up.

BENHUR LEE: –to Ira–

IRA FLATOW: Look at your radio.

BENHUR LEE: –right now. Right? And there’s one polar and then one non-polar end. And what you see in rubbing alcohol is isopropyl ethanol, which is just this, with this exact part. So these two hydrophobic ends and one hydrophilic ends. And what it does is exactly what Dr. Popescu said, is to basically destabilize the membrane. It’s a very biophysical process. And when it gets into the cell, it helps denature the proteins, as well.

I have to mention that more isn’t better in this case. If someone’s attempted and you have access to 100% ethanol, which you can buy commercially, not only is that dangerous, it does not work as well. You need a water solvent for the ethanol to permeate into the cells and dissolve.

IRA FLATOW: So you’re better to go to the drugstore, if you can still get it, and get the rubbing alcohol versus the ethanol alcohol isopropyl alcohol.

BENHUR LEE: You’re talking about hand sanitizer now, or just–

IRA FLATOW: No, just the alcohol itself.

BENHUR LEE: Yeah. I have it, and I dissolve it to make it up to 70% so I can cleanse my thermometer.

IRA FLATOW: Should we be making, Dr. Popescu, should we be making– I tried making my own hand sanitizer. I think I was pretty good at it. Is there anything wrong with trying that?

SASKIA POPESCU: I am personally not a big fan of it, simply because there’s a lot of room for error, and most of us aren’t great chemists in mixing our own things. So I prefer to go and buy them from the store, as long as they are at least 60%. And I’ve seen a lot advertised, you know, with glitter and scents in them. And I’m very hesitant about people making their own because there’s so much room for mistake. And then if you are not getting that minimum of 60%, it’s not going to be efficacious. And that can be very misleading, and give you a false sense of security.

IRA FLATOW: Let me ask you, Dr. Lee, when I was in the store– and I got there early, because that’s the kind of person I am, and they still had stuff on their shelves– most of this stuff I found did not have any alcohol in it at all. And yet all we hear now is about 65%, 70% that we need. Are these other products effective?

BENHUR LEE: Give me an example of kind of active ingredients in there. Alcohol-based wipes or sanitizers is not the only thing that works. So if you want me to give an example, I will explain.

IRA FLATOW: Chloride, [INAUDIBLE] chloride compound?

BENHUR LEE: So chloride– sodium hypochlorite is what you find in bleach wipes. And that can be tough on your hands, but as a disinfectant for surfaces, that works really well. Just to boil it down, it simply is a very reactive molecule, and it oxidizes, which means it destroys a lot of biomolecules. And that’s how it works. Another common one made off of quarternary ammonium chloride salts. And I actually bought it for you here.

IRA FLATOW: Here’s another molecule in here.

BENHUR LEE: So it’s kind of fatty acids, dimethyl benzene chloride. It’s one of those, and you come in many forms. And what you have here is an ammonia molecule and a chloride is actually not stuck to it. It’s charged, but it comes to it. And then you have a benzene molecule.

IRA FLATOW: We got to get you near the mic so here.

BENHUR LEE: We have a benzene molecule if you ignore all the rest. So what happens is you have a very hydrophobic N. And this, the blue stuff that you see here, it’s the charge part. Right? And so that likes to go to the negatively charged. This is possibly charged. And everything is hydrophobic. And it just disrupts, you know, this is big and bulky and it’s fat. And so it disrupts the lipid membrane. And that’s how it works.

IRA FLATOW: Saskia, what are hospitals doing? How do they differ then how we keep clean?

SASKIA POPESCU: Well I do want to say something first. When we’re talking about disinfecting wipes, it is so important that people don’t use those on your hands as a cleaning tool. I’ve seen that recently. So I just wanted to make that comment.

IRA FLATOW: Because?

SASKIA POPESCU: It’s just it’s a harsh chemical, and it’ll hurt your hand. You know what that would be like if you used a ton of hand sanitizer in a couple of minutes. That’s going to dry out your skin and potentially cause breakdown. So that’s why when you are using disinfecting wipes, it is important to kind of give your hands a rinse off right away, or just not use them to clean your hands. Clean surfaces with them, but don’t use it as a wipe just on your hand.

So for the health care side, hospitals are using the traditional disinfectants and cleaning tools. In health care we have sterilization which removes all microbial life. But then we have cleaning and disinfection. And cleaning helps remove the dirt. Disinfection helps minimize or eliminate microorganisms on surfaces. And we use a range of different products, whether they are disinfecting wipes and sprays or UV pulse robots to help destroy some organisms in the room. Additionally, these are all strategies we’ve been employing for decades. And it’s just a good time to remember that surface cleaning and disinfection is really important during this time because it’s still flu season. And if you touch a dirty surface and you don’t clean your hands and then you touch your eyes, that’s a great way for organisms to transmit. So these are things that we’re continuously doing and we’re just reinforcing more now.

IRA FLATOW: Can you apply what you do in the hospital to around our homes? The same kind of disinfectants?

SASKIA POPESCU: Definitely. So you’re not going to be using that high level like accelerated hydrogen peroxide or quaternary ammonium in your home because those are very high level, they’re harsher disinfectants. And you’re not going to need those for the home setting. But what you can do is use a disinfecting wipe. The big thing is making sure it’s EPA registered, and the big push is obviously an EPA registered disinfectant that is approved for with the emerging viral pathogen claim. And that simply means that when a novel pathogen occurs, if you look at the claim and it’s effective against the same organism.

So in this case, if you’re looking at a bottle of disinfecting wipes and it says that it is effective against coronaviruses, we know it will be effective against this new strain of coronavirus. So you just want to make sure whatever you’re using at home is EPA registered as a disinfectant. You can take that home, use those. You know, I’m that person that travels with my little travel thing of Clorox wipes. And I would like to wipe down the surfaces around me when I’m on an airplane. But clean your surfaces at home, your high touch areas, the refrigerator door, door knobs surfaces, counters, hard chairs, those kinds of things.

But then, also be mindful of your hand hygiene at home. Too often we focus on this when we’re out and about, but hand hygiene at home is so important and a subtle cue to yourself. But also, laundry is a key thing. This is big in health care. You know, laundering sheets and all other sorts of linens gowns. But at home too, make sure you’re not just going out and about and throwing clothes everywhere. You want to still clean your clothes.

I mean these are practices everybody does. But the big thing is, I always get asked, well what temperature should I use? And your normal dryer should be fine. 100 to 130 degree Fahrenheit for 30 minutes in a dryer tends to kill most microorganisms on clothing.

IRA FLATOW: If you leave your clothes out on the line to dry, will the sun, the ultraviolet, be good enough to kill the viruses? Let me just remind everybody first. You can think about that. This is Science Friday from WNYC Studios. Now you can take that breath.

SASKIA POPESCU: I would say maybe an Arizona summer. You know, I think it really depends on the temperature. I’m a big fan of using a dryer to get that heat. But this is, when we’re talking about COVID 19, this is not an environmentally hardy organism. It is an enveloped virus. It’s much easier to kill than a lot of the other microorganisms we worry about in health care that require harsher disinfectants like bleach.

BENHUR LEE: I second that thought actually, because people ask me what I do at home all the time. And we forget about the clothes that we wear around. And so a quick throw is easier for men with outer garments. But I throw everything into the dryer for 30 minutes and that should be enough to lessen the load even if it’s not zero.

IRA FLATOW: Quick question. Let’s go to the phones before the break. Let’s go to Daniel in Denver. Hi Daniel.

DANIEL: Yes, hello?

IRA FLATOW: Hi, go ahead.

DANIEL: Yeah, so there’s a preliminary study by the CDC that shows that the virus can exist airborne for up to three hours after it enters, and it can traverse ventilation systems. So I’m just trying to figure out how we protect ourselves from that.

IRA FLATOW: SASKIA POPESCU, have any advice?

SASKIA POPESCU: Yeah. so really that concern is when we’re doing aerosol generating procedures. That would be incubating a patient using BiPAP, things like that. Those are very unique procedures. And that’s simply because it pushes the organism out in the air. But for those patients that we’re concerned about with COVID 19, they’re in a very special room called a negative pressure room. And this means that it goes through a special filtration process and isn’t pushed out into the other air in the hallways in the hospital. So again this is a very unique situation for specific, more invasive medical procedures that can aerosolize particles

IRA FLATOW: Dr. Lee, is this virus any more any stronger from being killed than any other kind of virus. I mean, if you just take these simple measures. Is it a super virus or is it just super lethal?

BENHUR LEE: It’s actually not. It’s difficult in a public service to not people get sound bites away. So no it’s not a super virus. It’s a coronavirus. It has the same properties, biophysical properties as other coronaviruses.

It is true that some coronavirus viruses are made to cause gastroenteritis and this one is not one of those. They have other properties. But the point is that all the procedures that we are using, and as [INAUDIBLE] has mentioned will inactivate membrane lipid envelope viruses. It may differ in length of exposure to and activation regions. But all the precautions that are made will work.

There’s nothing particularly special about this virus. I want to be very clear here. What’s special about it, maybe, is that it seems quite contagious, and people shouldn’t take it lightly.

IRA FLATOW: OK, we have so many more questions so I don’t want to get into a half answer. So you can give us a call. 844-724-8255. Our Twitter [INAUDIBLE], wow. A lot of tweets coming in also. We’ll go to as many as we can. Talking about the coronavirus. I guess more than anything we’ve been talking about lately lately, and we will continue to talk about it. Stay with us. We’ll be right back after the break.

This is Science Friday. I’m Ira Flatow. We’re continuing with our ongoing special coverage of the coronavirus as things change very rapidly. And we’re talking about the science of sanitation in the age of an emerging pathogen with my guests epidemiologist Saskia Popescu and virologist Benhur Lee.

You know, lots of people are canceling flights for fear of catching the virus. Maybe you have. I certainly am. Indeed, the CDC currently discourages anyone, any high risk group, that means the elderly, those with underlying health conditions, discourages them from traveling by plane.

But what if you can’t avoid it? How do you keep yourself virus free or protect your fellow travelers from anything that you may be carrying? Well, here to talk about that is Dr. Vicki Stover Hertzberg, professor and director of the Center for Nursing Data Science at Emory University School of Nursing. Welcome to science Friday!

VICKI STOVER HERTZBERG: Thanks for having me, Ira.

IRA FLATOW: We spoke to you a couple of years ago, you might remember, when you first published your research on the airplane microbiome.

VICKI STOVER HERTZBERG: Yes.

IRA FLATOW: And what did you find in that research?

VICKI STOVER HERTZBERG: In the airplane microbiome we found that the bacteria that live in the or that you can find on an airplane appear to be very similar to those in any area where people spend a lot of time in.

IRA FLATOW: Yeah, and OK. Let’s talk now about the viruses and how the air circulates when you fly. What are the steps we should take to keep ourselves safe?

VICKI STOVER HERTZBERG: Here’s what I do. I book a window seat. You’re most at risk from the people that are seated one row ahead of you, one row behind you, and two seats on either side of you. By booking that window seat, you eliminate all those people to one side of you at least.

I don’t move because that reduces my exposure to people in other parts of the plane. I keep my hands very clean, and I’m constantly using hand sanitizer. I don’t touch my face. That’s really difficult. It’s tough to train yourself to do it, but that is one benefit, I’d say, of those Elizabethan collars that they put on dogs. You could imagine that. And I stay well hydrated.

And those are the steps that I take to try to ensure that I don’t come down with the virus. Oh, and there’s one more thing, that I don’t turn that vent on that’s above the seat.

IRA FLATOW: Because?

VICKI STOVER HERTZBERG: Because if somebody else around you is coughing or sneezing, and it’s not just a matter of coronavirus, it could be a cold, it could be influenza, that the spittle that they’re emitting, normally without any other forces that goes about three feet in front of them and then gravity takes it to the floor. But if you’ve got that vent from above coming down at you, it’s going to attract those droplets from the person next door to you or another seat away and bring them into that airstream and then be putting them all over your face.

IRA FLATOW: So you’re sort of setting up this circulation pattern, the air going down and sucking up the other bad stuff around you.

VICKI STOVER HERTZBERG: Right.

IRA FLATOW: Yeah. What about wiping down the tray?

VICKI STOVER HERTZBERG: I would recommend that as well. I didn’t used to think about that, but those typically are the things that we find in places where people spend a lot of time. That’s what we found are the bacteria there. And when we also looked at the viruses that we got in our samples, we sampled air, and we sampled surfaces, including the tray tables, they were all negative for a panel of 18 respiratory viruses. at that time.

The majority of our flights were in flu season. So we would not have been surprised to have seen influenza as a positive result on at least one or more of those. But the fact that they were all negative gave me a certain level of confidence that perhaps the ventilation systems are working the way they should be.

IRA FLATOW: Let me bring on my other guests, Dr. Saskia Popescu, Senior Infection Prevention Epidemiologist for Hope Health in Phoenix, Dr. Benhur Lee, Professor and Chair, of Microbiology at Mount Sinai Icahn School of Medicine here in New York. Our number, 844-724-8255.

So many questions. Let’s go to the phones because I’ll just sit back. And let’s go to Bridget in Laramie, Wyoming. Hi Bridget!

BRIDGET: Hi! My concern is with all the sanitizing we’re doing, is it possible we’re going to kill the good biome around us? And if we do that, can we learn to re-establish it like we are with probiotics in the gut biome?

IRA FLATOW: Dr. Lee, is it is too much of a good thing? I mean, are we going to be killing off the good stuff and creating super bacteria perhaps?

BENHUR LEE: You know, too much of anything is a bad thing. Salt will kill you if you take too much of it. Right? So let’s get past through this crisis first. I think there’s definitely truth to the fact that we do have a healthy skin biome, but the microbiome feel, it’s still very young in its infancy. So I say, let’s you know, the guests before flattened the curve. Help stop the spread of the epidemic. Bring the R0 down to one, and then we can worry about things later.

IRA FLATOW: I have a tweet here that is something I have been wondering myself from Rebecca, who says, is there a good way to clean fresh produce when you bring it home to stop contamination and spreading germs? Saskia, what do you think?

SASKIA POPESCU: I can’t give you the exact ratio. But I learned very long ago when we were doing epidemiology and food safety that when it comes to things like melons that are a little porous and difficult to cut without cross contaminating, soaking them in a very, like 1 to ten I think, don’t quote me on that actually, bleach to water ratio is nice. Just to put them in there to soak them to clean the outside, and then you can cut through without disinfecting it, or without cross contaminating it.

BENHUR LEE: One to ten is right.

SASKIA POPESCU: But you know, I would have to look up the ratio because I don’t want to misquote anybody. But that kind of teeny little bit of bleach in water is always helpful.

IRA FLATOW: Well, and I’m thinking if soap and water is good enough for your hands, why not soap and water on your peach or your apple?

BENHUR LEE: That could work too.

IRA FLATOW: That could work. Wow. We’ve just discovered a cheaper way!

BENHUR LEE: You just have to make sure you get rid of the soap. I mean, the vegetables that come out these days are actually, some of them are gamma radiated and stuff, but you have no control of who handles them in the supermarket. So whatever was just suggested is a legitimate way of doing it.

IRA FLATOW: Mm-hmm. OK, let’s talk about something that everybody is thinking about. And I was walking to the studio here in the streets of New York which are mostly, a lot of them empty. What do you do when you’re negotiating in the public? We talk about trying to thin out the public, and that’s how we flatten the curve. Right? What do you do Dr. Lee?

BENHUR LEE: I have very strong opinions about this, and people will disagree, especially in America. So I understand the message that wearing masks is not protective. It helps protect people who are infected against others. But that’s being disingenuous. The government should have prepared for more masks.

I would just point to the example of Hong Kong, Singapore, Taiwan, for example, and South Korea. Everyone has been trained over the years to wear masks and undergo preventive measures, especially after the SARS crisis. Right? And look at Hong Kong. It has the densest population in the world, more than in New York. They have cases. Look how many cases they have! They’ve literally stopped it in their tracks because everyone wears a mask. Everyone.

And you look at the epidemiology now, the flu has plummeted. Rhinoviruses has plummeted. Yes, it’s because those people infected are not coughing it out. If everyone participates without these caveats here and there, then it helps. I talked to hospital infection control. They say that, oh, it’s not the culture here. But I don’t care. If I wear a mask–

IRA FLATOW: But do you have to know how to wear the right one and wear it correctly?

BENHUR LEE: In hospitals, I want to make very clear. For people in high risk situations, N95 mask needs to be fitted. But everyone can be taught. Even a surgical mask needs to be taught to wear correctly. You have to nip it at your nose. You have to cover your face. But like every little bit helps. I gave some to my cab drivers.

IRA FLATOW: Dr. Popescu, agree?

SASKIA POPESCU: I just wanted to say, I mean there’s two pieces to this. One is wearing a mask. If you’re sick it’s helpful, but I too often I see people wearing it and not practicing any of the other infection control strategies like hand hygiene and avoiding touching the rest of their face. But the other piece to this is people are often wearing these surgical masks for such a prolonged period of time that they’re becoming damp and moistened and really losing their efficacy.

So part of it is, if you’re going to wear a mask because you’re sick, you can’t wear it all day. It’s going to get too wet to actually truly filter. And the other pieces is when you’re taking it off, not contaminating it, not touching the outside of the mask repeatedly, but also just remembering that is one piece of infection prevention measures, and there are a lot of other ones we need to engage in.

BENHUR LEE: Absolutely, and take that opportunity to educate everyone that has a mask on.

IRA FLATOW: OK, that’s about all the time that we have.

VICKI STOVER HERTZBERG: The other thing that a mask will do is that it will prevent you from touching your face. But it does no good if you then, you’re wearing your mask and then you reach underneath and scratch your lip or something.

IRA FLATOW: Yeah, those are all good points. Let me thank my guests Vicky Stover Hertzberg, Professor and Director of the Center for Nursing Data Science at Emory University, Dr. Benhur Lee at Mt. Sinai Icahn School of Medicine, and Dr. Saskia Popescu, Senior Infection Prevention Epidemiologist for Hope Health in Phoenix. Thank you all for taking time to be with us today.

BENHUR LEE Thank you, Ira.

VICKI STOVER HERTZBERG: Thank you for having us.

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