Note: Transcripts may contain errors. If you wish to re-use all, or part of, a transcript, please contact CBC for permission. Please check the corresponding audio before quoting in print. Copyright © CBC 2023

The Dose Transcript for March 1^st, 2023

Host: Dr. Brian Goldman

BRIAN GOLDMAN: Hi, I'm Dr. Brian Goldman. Welcome to The Dose. Well, it's norovirus season in Canada, in case you didn't know. Cases have been increasing over the past couple of months, both nationally and in several provinces. I've seen more cases of norovirus lately in the emergency department, and I can tell you that it spreads easily. I've had it three times and I'd much rather not have it again. So this week we're asking what is norovirus and how can I avoid it? Hi, Angela. Welcome back to The Dose.

ANGIE RASMUSSEN: Thanks so much for having me, Brian.

BRIAN GOLDMAN: So I just confessed to having norovirus three times. Have you had it before?

ANGIE RASMUSSEN: I think I've had it once. I've never been formally diagnosed. But given the symptoms, it seems pretty clear that's probably what it was. I was also an adult. Rotavirus and some other viruses that can cause gastroenteritis like that tends to affect children more. But this was a pretty unpleasant experience with pretty severe gastroenteritis that kept me in the bathroom for a couple of days.

BRIAN GOLDMAN: Yeah, we're speaking with you because you're an esteemed virologist, but the fact that you have some personal and of one experience, some doesn't hurt when it comes to to explaining just how unpleasant this disorder is. But before we get into all of that, can you give us a. Hi, my name is. Tell us what you do and where you do it.

ANGIE RASMUSSEN: Sure. I'm Angie Rasmussen. I'm a virologist and a principal research scientist at the Vaccine, an infectious disease organization, or VIDO at the University of Saskatchewan, also an adjunct professor here in the Department of Biochemistry, Microbiology and Immunology. And I study the host response to emerging viruses. I actually don't directly study norovirus, although I'm extremely familiar with it, as it is a RNA virus which falls right into the category of viruses that I work with.

BRIAN GOLDMAN: Okay, so you're the right person to ask these questions. As an emergency physician, I have diagnosed norovirus. You know, gastroenteritis. You know, we don't we don't do we don't get viral cultures typically. But clinically, I've diagnosed what I suspected was norovirus hundreds of times. So So give us your take on norovirus. You started to to mention it as a as an RNA virus. Can you say more about that?

ANGIE RASMUSSEN: Yeah. So norovirus is a type of virus that's called a calicivirus. It's a non enveloped virus, which means that it doesn't have essentially a cell membrane on its surface the way that many viruses do, so SARS, coronavirus 2, influenza, Ebola. All of these are envelope two viruses. And what that really means, why that significant is that they tend to be less stable when they're going through the highly acidic environment of the stomach. And that's why a lot of these viruses that typically cause gastroenteritis like like norovirus are non envelope so that they can survive that trip through the stomach acid.

BRIAN GOLDMAN: Okay. I mentioned in off the top that we're hearing more cases that there are more cases lately. And and I guess the question I want to ask is, are we back up to the pre-pandemic levels or did the you know, did the number of cases actually drop during the pandemic? What do we know about that?

ANGIE RASMUSSEN: So cases did drop during the pandemic and they they dropped in all throughout North America, as far as I'm aware, at least in Canada and the U.S. And I think a lot of that is probably because people were staying home more people were perhaps being a little bit more diligent about handwashing, even though that's not necessarily the best intervention for preventing COVID. People were more conscientious of that and they were just mingling less, eating out at restaurants, less doing things, less that would lead to norovirus transmission. So before the pandemic, norovirus kind of comes in and in surges like many things, because it is a very, very infectious virus, meaning it can really rapidly spread whenever it gets into a population that susceptible. And most people are. So we've had, you know, these big sort of peaks and valleys with norovirus. There are a lot of high profile norovirus outbreaks when they're they're occurring on a cruise ship or in a hotel. There have been a lot of norovirus outbreaks like that in the past. And if people are just doing those types of activities, less obviously there weren't there weren't a lot of cruises going on during the peak of the pandemic.

BRIAN GOLDMAN: Right.

ANGIE RASMUSSEN: So there weren't as many opportunities for people to get norovirus. But now that people are traveling again, they're going out more, they're eating out more, they're seeing other people. All of those are very conducive situations to getting norovirus.

BRIAN GOLDMAN: You know, this is just as an aside, which of the two factors do you think is more important, the fact that more people are congregating or that they're not washing their hands? I know there's a key. Message in there, and that is to wash your hands thoroughly. We'll get to that. But. But what do you think?

ANGIE RASMUSSEN: Yeah, I think it's probably more having to do with the congregation and actually also the eating out. So norovirus can actually be transmitted a few different ways. One is through what, indirect transmission or fomite transmission that's picking up the virus off of the surface. And we can talk about that a little bit more, but it can also be transmitted by eating it. It is a foodborne illness. So sometimes you don't even have to be around people to get it, but you might have to be around people to spread it to others because you can get it from eating food that's contaminated with it. And the third way that you can get it is actually through probably consumption of aerosols that you inhale. So when you inhale something that goes into your nose, it also goes into your throat. And that can be swallowed. And when you vomit or have diarrhea or flush the toilet a lot, that does generate potentially a lot of infectious aerosols. So the the aerosol route is thought to be one of the mechanisms of norovirus transmission. And that would absolutely be relevant in situations where people are congregating.

BRIAN GOLDMAN: So you can actually inhale norovirus particles and get infected that way. Wow.

ANGIE RASMUSSEN: Yes. And although it's you know, I think this is something that's not really known. It's hard to say if you actually get that because the norovirus that infects the epithelium in your nose. Like I said, I think it's probably more that people are inhaling the aerosols and then they're swallowing them.

BRIAN GOLDMAN: Got it. Okay. So and as you've already said, norovirus, you know, a lot of people can get it by touching a contaminated surface. So that could be a countertop, a doorknob, a flush, like a tap or a flush toilet handle. And and and then and then putting their finger in their mouth. And now they've become in or into their eye or into their nose. So that leads me to your question. How long does norovirus survive on those surfaces?

ANGIE RASMUSSEN: So that's also why it's important that it's a non enveloped virus. So these non envelope viruses are much hardier than than viruses that have envelopes because the viruses that have envelopes can be those envelopes can be more easily disrupted. So like SaaS coronavirus two, for example, is an envelope virus. If you disrupt that envelope with with hand sanitizer, with a disinfectant, with detergent that basically gets rid of the envelope and also all the spike protein that's on the surface of the virus particles. So it's not infectious anymore. That's not the case with norovirus. So it can withstand hand sanitizer. And that's why really the best way to get rid of norovirus on your hands is by washing them frequently with soap and water and washing them for at least 20 seconds.

BRIAN GOLDMAN: How contagious is it? You know, for every infected person, what do we know about how many others will get infected? For every person who who brings norovirus into the home or into a cruise ship?

ANGIE RASMUSSEN: Yeah. So this is also like the environmental stability. This is really dependent sometimes on the circumstances. And there are some types of norovirus that are thought to. Some people are more resistant to them than others. So that's that's a factor in terms of calculating the R number or the number of people that an infected person will go on to then to transmit the virus to. It also has to do with how they're interacting with each other and what their exposure is. But one thing is for certain, and that is norovirus is incredibly infectious. You can become infected productively with norovirus by exposure to only a handful, you know, fewer than ten infectious particles. And that is among one of the most infectious viruses that we know about. Probably some other comparators would be things like measles virus. But usually you you need to be exposed to more a higher dose of the infectious virus than with norovirus. It is extremely infectious and therefore extremely transmissible.

BRIAN GOLDMAN: My sense in the emergency department is that the diagnosis is clinical, meaning it's based on the typical symptoms, but is there a test for it?

ANGIE RASMUSSEN: So, yes, you can test for norovirus. There's a you can it's usually a PCR test. Most people don't try to culture norovirus and viral cultures, not necessarily, as you know, a major diagnostic method, but you can do PCR to test for norovirus in stool or in in vomit. And that that can tell you what type of norovirus you have. That also helps people who are doing genomic epidemiology track different strains and types of norovirus as they spread throughout populations. It also helps in terms of outbreak investigation. So if we know that, you know people. We're getting norovirus and we don't really know what the source was. It can sometimes be traced back to something that they ate by doing that type of genomic surveillance. It can also be potentially traced as it spreads through an environment like a cruise ship or a daycare or what have you.

BRIAN GOLDMAN: As you've already mentioned, norovirus typically causes a self-limited disease that's over and done with kind of maximum 48 hours. But, you know, I've certainly had it where it was gone. You know, the worst of it was over after about 16 to 24 hours. Some patients, though, get it worse. And what are the kinds of patients who are most likely to need to either visit a doctor or go to the emergency department?

ANGIE RASMUSSEN: So certainly in general, people who are medically fragile are going to always have worse outcomes with really any kind of gastroenteritis because of that dehydration issue. It puts a lot of stress on your body in a very short period of time. And certainly if you get too dehydrated, that can cause all sorts of other problems. So certainly anybody who is is medically vulnerable has a lot of other co-morbidities. But also in immunocompromised people, it can sometimes be very difficult to clear gastrointestinal infections because your immune system isn't working properly and doesn't necessarily clear the virus right away. Now, this isn't as much of a problem for norovirus as it is for some other viruses that that do infect the GI tract, like polio virus, for example, often doesn't actually cause any sort of gastrointestinal disease. It causes polio myelitis, which is a huge problem if you're not vaccinated for it. But people who have been vaccinated actually with live attenuated polio vaccines in some cases can shed the virus for sometimes years afterwards. And and often those people are people who may not even know that they're immuno compromised. So that's something I'm not sure that has been investigated very thoroughly with norovirus. But certainly people who are immuno compromised are more likely to have worse outcomes. Also, people who have any kind of inflammatory bowel disease, any kind of inflammatory gastrointestinal condition will undoubtedly find their disease course with norovirus to be a lot less. Not that anybody finds it pleasant, but they might find it to be even worse than than your average person who doesn't have those conditions.

BRIAN GOLDMAN: We've said that norovirus is usually a self-limited, not particularly serious disease, but it can be very serious for infants in the developing world, right?

ANGIE RASMUSSEN: Absolutely. So, you know, for some of these viruses that cause gastroenteritis, like rotavirus, for example, there are vaccines. But even so, in places where those vaccines aren't readily available, if people choose not to vaccinate, and especially in low and middle income countries where those vaccines just aren't accessible to people, these viruses kill a lot of children. And it's it really is very, very dangerous for for young kids to get things like rotavirus, but also to get norovirus. And children certainly can get it. It's not something that you only get as an adult. So especially if you have little ones and you suspect they might have norovirus, that's something you really need to make sure that that you are keeping them hydrated. Since there is, of course, no vaccine at this time for norovirus.

BRIAN GOLDMAN: So people are contagious for as long as they're continuing to shed virus in their vomit and and in their poop. So how long does that last?

ANGIE RASMUSSEN: So that usually, fortunately, does resolve with the symptoms. And that's thought to be one of the reasons why the onset is so rapid and also why the recovery and the disease is is self-limited, as you said, and and relatively short time course for most people. And that is that once the virus gets effectively cleared, which it does rapidly because so much virus is being produced all at once, it really does stimulate your immune system to to get on that, then people aren't really shedding virus for a long period of time afterwards.

BRIAN GOLDMAN: Being a virus, of course, norovirus has no antibiotic treatment. Is it basically symptomatic treatment? You know, things like, you know, anti-nausea, it's like diamond hydronate or Gravol all which is over-the-counter ondansetron. We use a lot of Ondansetron or Zofran in the emergency department. That's a prescription medication.

ANGIE RASMUSSEN: Yeah. So it is really about treating the symptoms for the most part. And typically, I think if people have a more severe course of illness, then rehydration is obviously really, really important. So making sure that people are not, you know, getting their electrolytes thrown out of whack and making sure that people have sufficient hydration. Right now, it would be very difficult, I think, to actually make an effective norovirus therapeutic. And part of the reason for that is it is such a short course of disease. So you'd have to really essentially start taking whatever you were going to take. At the moment that you became symptomatic for it to have any effect. And as you said, you know, a lot of times it can be less than 24 hours before the disease runs its course. That's not really a very big window of time to apply a therapeutic. So we'd really be better off thinking about norovirus vaccines, which is I think people are definitely working on that. But there is currently no available norovirus vaccine either.

BRIAN GOLDMAN: I want to close with what I think is a critical issue, and I want you to, you know, based on everything that you've said and with your expertise as a virologist, you know about the behavior of the virus and how it how hearty it is at remaining on contaminated surfaces, give us your best advice on how all of us can do our best to try to prevent the transmission of the virus if we happen to have somebody in our household who we think has norovirus.

ANGIE RASMUSSEN: Yeah, So this is tricky because if it's in your household, it's very, very difficult to prevent exposure, even if you're, you know, in separate rooms, if you go essentially into that person's presence, especially if you go into the bathroom, if that's where they're hanging out or if they've got, you know, a bucket next to their bed, then you might be exposed to two aerosols. So I guess the best way to prevent that would be the way that we deal with COVID, and that is to wear a well-fitting mask and ideally and well-fitted N95 respirator or another type of respirator that will keep most of those particles out. The other thing that's really important to emphasize is washing your hands with soap and water, not using hand sanitizer, because hand sanitizer actually doesn't work very well against norovirus. But washing your hands with soap can remove any virus that that might have gotten onto your hands. Now, this is why it's really hard to prevent, though, because people who are sick with norovirus are shedding, you know, in the orders of potentially tens to hundreds of billions of virus particles. My God. Yeah. And that's that's quite a lot. So even if you can wash your hands and remove most of those, remember, you only need to get exposed to a few of those particles to get infected yourself. So the ideal thing to do, but especially if you're medically fragile and somebody else in your house does have norovirus, would be to completely steer clear of them if you have to be around them, even if you have to use the same bathroom as them, then try to wear an N95 mask. Make sure your you're washing your hands very, very well and frequently. And then finally, the last thing I would suggest is surface disinfection, potentially with a more heavy duty disinfecting compound. So a type of bleach derivative, you know, there's household spray cleaners and things that have bleach in them, that that would be good, although that's not going to be useful on every single surface. So but definitely don't rely on on hand sanitizer to to cover all of it, because you really do need to take a multi-pronged approach. And also think about your aerosol exposure.

BRIAN GOLDMAN: The thorough scrubbing is, you know, one or two dollops of, you know, like a dollop of soap, one or two pumps of the of the soap dispenser, liquid soap dispenser, and thoroughly scrub your hands for at least 20 seconds.

ANGIE RASMUSSEN: Yeah, 20 seconds. And, you know, pretend like you're in a show about surgeons or something and you're scrubbing in. Like, get under the nails, get, you know, do do a really thorough hand-washing job, more thorough than I think a lot of people do. Because, again, this isn't going to help against every single pathogen that you might encounter. Certainly, it helps a little bit with things like like influenza and COVID in the common cold. But it really is going to help out here a lot.

BRIAN GOLDMAN: I've had you know, it's been it's been suggested to me by microbiologists that while you're scrubbing your hands, if you sing Happy Birthday to the Happy Birthday song, you know the birthday song, Happy birthday to you. If you if you and don't race through it, just sing it as you would somebody in your family. By the time you get to the end of the song you you will have done at least 20.

ANGIE RASMUSSEN: Yeah, that sounds like a good plan. I've also heard sing the chorus to I Will Survive. I think that Gloria Gaynor actually did that early on in the COVID 19 pandemic, back when hand-washing was a, you know, a top recommendation for that. But yeah, if you need to use a song, anything like that, that that can keep you there for 20 seconds at least, and it's okay to do it for 30 seconds and 40 seconds, that's fine too. But just make sure that you're doing a really, really thorough job and that you're, you know, really scrubbing, really using enough soap. And, you know, you can also use warm water that makes it a little more pleasant. But make sure that you're very thorough with that.

BRIAN GOLDMAN: One way or another. Angela Rasmussen You will survive, but but, but it would be so much better if. You don't get norovirus. Thank you so much. Any time for talking for talking about this very important virus. And hopefully some people will not get it as a as a result of what you had to say.

ANGIE RASMUSSEN: I'm really happy to be here, and I'm especially happy to contribute to the cause of less norovirus.

BRIAN GOLDMAN: Angela Rasmussen is a virologist at the University of Saskatchewan's vaccine and infectious disease organization Beat Out. Here's your dose of smart advice. Norovirus is a highly contagious virus that you can get from having direct contact with an infected person or consuming contaminated food or water. You can also get it by touching contaminated surfaces like countertops and doorknobs, and then putting your unwashed fingers in your mouth or nose because the virus spreads very easily and quickly. Outbreaks are common. They happen anywhere and anytime people congregate indoors. The most common symptoms are diarrhea, nausea, vomiting and abdominal pain. Symptoms develop 12 to 48 hours after being exposed to the virus. Most people with norovirus illness get better within 1 to 3 days. There are no antibiotics to treat it. Prescription and over-the-counter medications treat nausea and vomiting. Those medications are important because you must keep drinking fluids so you don't get dehydrated. The symptoms of dehydration include decreased urination, dry mouth and throat weakness and dizziness. People at increased risk of dehydration include infants and young children, older adults and people with severe chronic illnesses. You should seek medical advice or go to the nearest emergency department if you have symptoms of dehydration or if your nausea and vomiting are so severe that you can't drink fluids because norovirus is extremely contagious. You must do your bit to prevent it from spreading by disinfecting surfaces and by scrubbing your hands thoroughly with soap and water every time you touch a surface that may have been contaminated. If you have topics you'd like discussed or questions answered, our email address is the dose at cbc.ca. If you liked this episode, please give us a rating and review wherever you listen. This edition of the Dose was produced by Stephanie Dewar. Our senior producer is Colleen Ross. The dose We want you to be better informed about your health. If you're looking for medical advice, see your health care provider. I'm Dr. Brian Goldman. I'll try your next dose.

Back To Top »

Provide Transcript Feedback

CBC would like to acknowledge the support of the Broadcasting Accessibility Fund.

What is norovirus and how can I avoid it? - Transcript

More Stories Like This