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The Dose Transcript for January 16, 2025

Host: Dr. Brian Goldman

BRIAN GOLDMAN: Hi, I'm Dr. Brian Goldman. Welcome to The Dose. A respiratory virus is getting a lot of media attention. It's called human metapneumovirus, or HMPV. There's been a surge of cases in China. That fact alone has made some people worry that it's another pandemic. So this week we're asking: What should I know about human metapneumovirus? Hi, Satchan. Welcome to The Dose.

SATCHAN TAKAYA: Hi, Brian. Thank you very much for having me today.

BRIAN GOLDMAN: So how bemused have you been by the coverage of this particular virus in the media?

SATCHAN TAKAYA: Bemused is a very good word. It's been interesting to see how much attention this virus is getting. In our infectious diseases world, human metapneumovirus isn't a big deal. But it's become a big deal in the media and so it's very interesting to watch this play out.

BRIAN GOLDMAN: You're the expert. Bemused is a reassuring term, so I'm certainly looking forward to what you have to say about this particular virus. But before we get to that discussion, can you give us a hi, my name is? Tell us what you do and where you do it.

SATCHAN TAKAYA: My name is Dr. Satchan Takaya. I'm an adult infectious diseases specialist in Saskatoon, and I'm currently the division lead and a clinical associate professor with the University of Saskatchewan Division of Infectious Diseases.

BRIAN GOLDMAN: First of all, what is human metapneumovirus?

SATCHAN TAKAYA: So human metapneumovirus, it's another respiratory virus that's out there. It's an RNA virus and it belongs to the family called the Pneumoviridae family, which also has RSV in it, so respiratory syncytial virus that people have probably heard about in the news as well. It's also part of that family. And it's new because it has a new name as of a few decades ago. So it was discovered in 2001, but we believe that it's been circulating for decades before, like 50, 60 years it's been out there as just kind of a regular cold virus. But it gained the name in 2001. And it's gradually seeping into our, you know, our daily clinical care. And so it's piqued interest, I think, because of the new name, but it's not a new virus. And it circulates around like it does with many other cold viruses, and it's very seasonal. It happens along with flu viruses and other cold viruses in the northern hemisphere when the cold season hits. And so while it's gaining attention, it's not a new virus. It just has a new name.

BRIAN GOLDMAN: This time of year, we're seeing lots of cases of influenza and RSV, which you've already mentioned. Another important respiratory virus. So how does human metapneumovirus compare to these in terms of the number of cases that we're seeing?

SATCHAN TAKAYA: The number of cases are going up because it's the cold season, right? So it's winter season, and so we're seeing what people are referring to as a surge of infection. But it's, it's expected. We expect that whether it's in Canada, the States, the U.K., China, it goes up because it's the time of year to have these viruses. So we are seeing an increased number compared to what the baseline would be, but it's not unexpected. And if you look at the numbers in Canada, our test positivity, so that's, how many of the tests that are done are actually positive for human metapneumovirus. And it's quite low. It's at 1.9% nationally. And this is based on respiratory viral surveillance network that PHAC has on their website on the Health Canada site. It's getting a lot of media attention, but it's only at 1.9%, versus influenza or RSV that's up at 11%. And even in China, you know, the numbers are quite low relative to influenza. So they have their own CDC site that has their own weekly surveillance and reports. And according to the Chinese Center for Disease Control, their last week of December test positivity was at about 6%. Which is higher than Canada, but is much lower than influenza, which is at 30%. And RSV, for whatever reason in China, is a little bit lower right now at about 3%. So, although it's making a lot of headlines, test positivity is incredibly low compared to the other viruses that are out there. And I think it's visible because it's being tested for right now. We're not testing for all the other cold viruses. So when you compare it to other cold viruses, which one is more? I don't know. We don't specifically look for the various strains of cold viruses either. So, in general, it's nothing out of the ordinary. And the WHO has reiterated that, too. In all of the media attention and panic, they've reassured people the numbers that we're seeing are not out of the norm.

BRIAN GOLDMAN: Certainly, people who listen to The Dose, if they're still listening right now, it's because they're curious about this virus. But I wanted to get back to China because that's the touchstone that has led to so much media attention. What's your sense of what the heck is going on in China right now as far as human metapneumovirus is concerned?

SATCHAN TAKAYA: Looking at the reports, and I think there's quite a bit of media out there about human metapneumovirus, and they all have the same message -- you know, not to panic, that it's the expected rates. So I think we see the visuals coming out, right, of health centres that are overcrowded with people wearing masks. And I think there's this fear out there that we don't want to go through a pandemic again. Like we all have very bad memories of the pandemic, many of us do. But despite those images, it's important to know that that's usual. It's not out of the usual. COVID was out of the usual. But this is people being in health centres. And we're seeing the same thing in Saskatoon, too. We have lots of people coming in with what we call ILIs, or influenza-like illnesses, because they're sicker than they normally are. But that goes up every winter. It's not unexpected. And so there's a lot of focus on China, I think, because that's where, you know, SARS-CoV-2 came from. And so there's a little bit of fear around there. But it's important to remember this is... despite what the images show, what's happening there is what happens every year. So, I don't think there's anything special happening. I think it's the fear that's driving that attention. It's like any other cold virus. I'm not sure if it was rhinovirus or if we named that a fancy name whether it would get the same sort of attention. I think it would get the attention because it was China. But really, there's nothing out of the ordinary happening there right now.

BRIAN GOLDMAN: How contagious is HMPV?

SATCHAN TAKAYA: It's as contagious as the other cold viruses. So we have a whole panel of cold. When you get a cold every year... People refer to colds as by different things, right? Some people say, I have the flu. But the flu in our medical world is influenza. And so this is different from the flu. We're talking about an upper respiratory tract infection where you get that runny nose and the cough. So it does transmit. It's a droplet/contact spread. It can also spread on non-porous surfaces. So if you touch or sneeze onto a surface, it can actually live on the surface for a couple of hours. So there is transmissibility for sure, but it's no more contagious than any other cold virus. So usual precautions should keep you from getting it. But it would spread in the winter months when you've got, you know, sneezes and coughs happening everywhere and people back to work and back to school. That spread happens. But we will get over it. It's not usually a terribly virulent infection.

BRIAN GOLDMAN: And are the signs and symptoms... You've described it as a cold, basically sore throat, runny nose, maybe a little bit of a cough and a low-grade fever, or is there more to it?

SATCHAN TAKAYA: Yeah, it's usual symptoms. So it is an upper respiratory tract infection. The virus attacks the epithelial lining of our airways. So it does cause coughs, sneezing, runny nose -- the usual symptoms. Doesn't usually hit the gut too much, so there aren't a lot of people that describe diarrhea or nausea or vomiting with this. Sometimes you can get a fever, sometimes you can get a rash. But those things also happen with our usual suspects of, you know, enteroviruses or adenoviruses. And so it's usually typical. But there are always, with any other infection, those people that if they have an underlying immune deficiency or if they're at what we call the extremes of age, so if they're very young or very old and their immune system isn't either primed to the virus or if it's not as responsive, then they can get more severe disease, so where that upper respiratory tract infection goes lower and becomes more of a pneumonia or bronchitis. And so, severe illness can happen, but it's not common. There is a recognition that it can cause childhood pneumonias, especially in those kids that have never been exposed before. So they say about 1 in 10 can progress to a pneumonia rather than just being kind of a runny nose in a kid.

BRIAN GOLDMAN: And you've already anticipated my next question. This is predominantly an infection that affects kids.

SATCHAN TAKAYA: Yeah, usually children. So similar to RSV, which is again, in the same viral family, it hits kids between ages one to five. RSV targets more of the really young, the infant population. But they say most kids by the age of five have been exposed. So if you check their antibodies, and I think there are studies that have done that, to say most kids, you know, a majority have antibodies to human metapneumovirus by the age of five.

BRIAN GOLDMAN: And how long are people usually sick?

SATCHAN TAKAYA: They say about seven to ten days the symptoms can last. So it depends on whereabouts, I guess, in the airway it hits. If it goes a little bit lower and gives you that extra cough for a little while it can last a little bit longer. But usually about a week. So you catch the virus-- the incubation period is about three to six days, they say. So you might be a little bit contagious for a few days before, and then your symptoms last for about a week and shouldn't be any heavier than a usual cold.

BRIAN GOLDMAN: For those people who are immunocompromised or who have severe chronic ailments like chronic kidney disease, chronic obstructive pulmonary disease, heart failure, how serious can HMPV get?

SATCHAN TAKAYA: I'm not sure how bad it can get. When people present to the hospital for whatever it is they present for, if they have a fever or any signs of a respiratory tract infection, we do this thing called the expanded respiratory panel, where we look for all the viruses and we find it. Right? So there are some that become positive for the human metapneumovirus. But in, you know, doing infectious diseases call, I've yet to see a severe case of metapneumovirus. There are some, because of their immune status, that can be predisposed to a secondary bacterial pneumonia. Once they get that viral infection in the chest, it kind of weakens the immunity in the chest. And so you get a bacterial infection on top of that, and then you can get a severe bacterial pneumonia. But to say that human metapneumovirus is a key trigger, it's probably not the case. I don't know the numbers per se, but I have yet to see a severe case of human metapneumovirus. I think with any chronic illness or condition that can weaken your immune system, we always worry about that virus causing that initial insult that allows other infections to settle in and cause the damage.

BRIAN GOLDMAN: And can you get, you know, what we call a co-infection? Have you seen that, where there's been human metapneumovirus and, say, influenza or another virus?

SATCHAN TAKAYA: It can happen. And we were worried about that during the COVID times, right? We were worried about what they called the twindemic with flu and COVID happening at the same time. I haven't really seen that specifically with human metapneumovirus. Usually, you know, it would be really bad luck to have two cold viruses at once. But in the tests that I've come across, I've never seen more than one positive. Like I'll see a rhinovirus positive here, a human metapneumovirus positive there. But rarely do we see more than one virus positive at a time.

BRIAN GOLDMAN: For the vast majority of people who get this, it's a mild ailment and they're going to be better in seven to ten days. For people who are more seriously ill, are any of the antiviral medications effective?

SATCHAN TAKAYA: No, we don't have any effective antivirals for human metapneumovirus. Similar to many other cold viruses, we don't have anything that's been studied to say, this is the drug for you. There have been some studies in the past looking at things like Ribavirin, but they haven't shown any true effectiveness. So there's no real therapy other than conservative management, where we make sure that your airways are supported, that your oxygenation is supported while your lungs rest and recover. It's important to make sure you seek medical attention early if you are one of those people that have a weaker immune system more susceptible to more severe infection, and you do get an infection that you're worried could settle in a little more seriously to make sure to see somebody so that you can get that conservative management started early and that we can watch carefully.

BRIAN GOLDMAN: How common is it to be reinfected with this virus?

SATCHAN TAKAYA: Probably fairly common. Very similar to other cold viruses, right? So the immunity isn't lifelong, but there is a component of memory. So as I said before, most kids are exposed by the age of five. And the severe illness in childhood is because they've never been exposed before. So it's that primary infection that can cause the severe symptoms. Once you've had the infection, on re-exposure... so, I think the immunity wanes. Usually, with most viral infections, it's usually about, you know, three, maybe at the most, six months. After that, your antibodies kind of settle down and would need to be re-stimulated. But on re-exposure, those antibodies, those B cells are re-stimulated, and you have more antibody production. So, it's never as bad the second time around. So I don't know if they've looked at specific studies to say, okay, your antibodies will fade by this time. I think in general, the principle is with respiratory viruses that that does settle down after a few months. So the reinfection is definitely possible and probably does in fact happen. But it wouldn't be as severe on subsequent exposures unless there was something that affected the immune response.

BRIAN GOLDMAN: I'm going to guess that there is no vaccine under development for this particular virus.

SATCHAN TAKAYA: You know, there is now. And I think it was all... you know what, COVID has changed so many things, right? And so with COVID, we had the mRNA vaccine technology come around. And so with that, there's been an interest in developing a human metapneumovirus vaccine using mRNA technology. So Moderna is actually looking at a vaccine in children that targets both RSV and human metapneumovirus at the same time. It's still in phase one. I think they've closed enrollment, but they're looking to see if it decreases complications such as lower respiratory tract infections and hospitalizations. So, interesting to see what'll come of that. I believe that with vaccines, though, we need to make sure that there's a need, right. So that if the illness itself is not significant, why would you get a vaccine for it? Similar to treatment. When you weigh the risks and benefits, if the benefits don't heavily outweigh the risks, there's probably no reason to pursue that. For most people, they probably wouldn't need a vaccine for human metapneumovirus. But for those children that have never been exposed, that are at risk, definitely a vaccine would be helpful to prevent those severe respiratory exacerbations and things. So it'll be exciting to see what comes of that. But I believe it's in the early phases. And that's all I could come across for vaccines. There have been vaccine development attempts in the past. So where they tried to develop what we call protein subunit vaccines, where they manufacture through recombinant technology, they looked for the protein of the virus, right, and inject that. But they've never been successful because as an RNA virus, there's always room for error. So with little changes year to year or even infection to infection, that protein doesn't look identical every time. So to give a vaccine against that protein, it doesn't always work. So I think in the past, like as far as ten years ago, they looked at some subunit protein vaccines. But I haven't seen that released yet, so I presume that they didn't work. But the mRNA technology is now being applied to the metapneumovirus as well, so we'll see where that goes.

BRIAN GOLDMAN: Finally, you know, everything that you've said is very reassuring when it comes to this virus, and yet there was a lot of media attention about it. You know, we can say that that's a bad thing, but on the other hand, the fact that people are more sensitized to the possibility of a new virus and more, perhaps more vigilant, is a good thing, isn't it?

SATCHAN TAKAYA: I think so. But there's so many viruses and so many infections out there, right? And the ones that hit the media are just a handful. I think we're all a little traumatized from the pandemic. It did something that we've never seen before and really turned all of our lives upside down. And so nobody wants that again. The fear that I have of too much attention on viruses, particularly when we say viruses from a certain country, it does stigmatize a little bit. And so I think it's really important to not panic and really gain an understanding of whether that virus is even an emerging threat. So, you know, we have emerging infectious issues all the time. And it's, you know, it's kind of an area of study on its own, emerging infectious diseases. But with a better understanding, it's important to put that understanding when the virus does show itself in the media or social media -- and with the media the way it is, it just... one signal and it kind of blows out of proportion, I find. And so, yes, knowledge is important. Knowing about the virus, sure, it's great. But you do need to have the knowledge behind it to understand that it's not going to harm. It's no worse than what we normally know what to do. So, I think education is very important when we see increasing media articles on new viruses or things we haven't heard before. Like, metapneumovirus is not new in the ID world. We've always known about it, particularly in pediatric ID, right? But it's not known in the general population. And even in the hospital, like I often get stopped by an attending that sees a positive human metapneumovirus on the respiratory panel and say, well, what is this? So it's not, it's not common knowledge. But at the same time, it's really important to know not to induce that panic. I think there's just been so much trauma from the pandemic that we just need to take a step back and make sure that there's good understanding so that we don't go down that spiral.

BRIAN GOLDMAN: And to finish the thought that you were saying, you were talking about stigmatization. I think you're talking about stigmatizing the country that is the origin country of an outbreak.

SATCHAN TAKAYA: It's unfortunate. I think, you know, the reason it happened from China is just because of the differences in populations or difference in... There's different viruses in different animal populations, and we have what we call reservoirs. So, zoonotic reservoirs that unfortunately had, you know, kind of wrong place, wrong time, and it became a virus that jumped to a human, right? But that happens everywhere. And it's funny that China seems to be predominant in the news for these viruses coming out. Like we have MERS, right, and I don't think anybody knows about MERS. [laughs] But that's a Middle Eastern Respiratory Syndrome virus, and it doesn't get nearly the same press that, you know, human metapneumovirus out of China comes in. And MERS is so much worse than human metapneumovirus, yet that stigmatization, I think, has a lot to do with the attention that it gets. So hopefully we can move away from that with more knowledge, right? The more you know about the virus, the better the understanding of how these viruses happen. They just happened to happen in China I think with the SARS-CoV-2, but it's something that could happen anywhere. We just have to be very vigilant.

BRIAN GOLDMAN: And we certainly know more now about human metapneumovirus thanks to you, Dr. Satchan Takaya. Thank you so much for coming on to The Dose to talk about it.

SATCHAN TAKAYA: Oh, thank you so much for having me.

BRIAN GOLDMAN: Dr. Satchan Takaya is an infectious diseases specialist and clinical associate professor and division head of infectious diseases at the University of Saskatchewan College of Medicine. Here's your dose of smart advice. Human metapneumovirus is one of several respiratory viruses that circulate across the world each year. HMPV is common. It's part of the same grouping of viruses as respiratory syncytial virus, or RSV. Much like the flu and RSV, rates tend to go up in countries such as Canada with cold winters. In China, reported cases of HMPV have been rising since December, particularly kids 14 years of age and under. The World Health Organization says the increase has followed the predictable rise in cases during the winter months. The virus spreads primarily through droplets or aerosols from coughing or sneezing, through direct contact with an infected individual, or through exposure to contaminated surfaces. Basically the same ways people get colds, flus and COVID. HMPV is similar to respiratory syncytial virus, or RSV. HMPV causes flu-like symptoms such as cough, fever, nasal congestion and wheezing. Most infections with the virus resemble the common cold. A smaller percentage of patients get bronchitis or pneumonia. Patients with pre-existing lung conditions such as asthma, chronic obstructive pulmonary disease or emphysema are at higher risk of severe outcomes. Others at risk include infants, older adults, and people who are immunocompromised. There is no approved vaccine against HMPV, though a vaccine developed for children has been clinically tested. Likewise, there are no specific antiviral medications recommended for the virus. The initial reports from China have sparked fears of another pandemic, but there are several major differences between COVID-19 and HMPV. We know a lot more about HMPV than we did about COVID at the start of the pandemic. When COVID first arrived, it was a new virus to which we were not immune, and many people got seriously ill. HMPV has been around longer, and there is a general level of immunity across the population. Since most people get a mild illness, it should not tax the capacity of our health-care system to deal with it. If you have topics you'd like discussed or questions answered, our email address is thedose@cbc.ca. If you liked this episode, please give us a rating and review wherever you get your podcasts. This edition of The Dose was produced by Sameer Chhabra. Our senior producer is Colleen Ross. The Dose wants 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. Until your next dose.

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What do I need to know about HMPV? - Transcript

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