The Decibel - A virologist on COVID variant XBB 1.5

Episode Date: January 11, 2023

The XBB 1.5 variant of COVID is quickly becoming the dominant strain in the US, and we’re seeing more cases here in Canada too. The WHO has called it the most transmissible variant of the virus we��ve seen so far.Some people are calling it ‘The Kraken.’ But not Dr. Angela Rasmussen. She’s a virologist at VIDO, the Vaccine and Infectious Disease Organization at the University of Saskatchewan, and she’ll walk us through what we know about this variant, what we don’t know, and how concerned we should be.Questions? Comments? Ideas? Email us at [e-mail]

The World Health Organization says we're seeing the most transmissible strain of COVID yet. This subvariant, XBB1.5, is quickly becoming the dominant strain in the U.S. And we're seeing more and more cases here in Canada. Dr. Angela Rasmussen is a virologist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan. And she has a PhD in microbiology and immunology. She's here to tell us about this sub-variant of COVID and why she really doesn't think we should be calling it the Kraken. I'm Maina Karaman-Wellms and this is The Decibel from The Globe and Mail. Angie, thank you so much for taking the time to speak with me today.

It's a pleasure to be here, Maynika. Let's just start with the basics here of this XBB 1.5 variant. Can you just start by telling me, when did it emerge and how did it start? So XBB 1.5 emerged probably a month or two ago. It was first detected anyways. Primarily, it's spreading right now in the northeastern United States, but it's a derivative of another variant that's been around since the summer called XBB, not very different in terms of its name. And that's because it's essentially the grandchild of XBB. It is a virus that resulted from people who were infected with XBB acquiring a couple mutations and becoming XBB 1.5. And in fact, that's what

those names mean. They refer to the virus's evolutionary lineage. And so what happened, I guess, when we're specifically talking about XBB 1.5, what happened to create this subvariant? Do we know? Yeah, we do, actually. So all of these, I think the first thing to point out to the layperson is that all of these different variants, this whole alphabet soup of subvariants that we've been hearing about, are all Omicron. Unfortunately, because the virus has had so many opportunities to replicate as it's been spreading through the human population, we've been seeing ever more of these subvariant children, if you will, emerging. So there were two sub-variant lineages of BA2, and they recombined. And that's

essentially when a person is infected with two of these variants at once, and they essentially cut and paste their genomes together to make what we call a recombinant genome. So this is actually a combination of two different BA2 derivatives that then went on to infect other people and acquired still more mutations and became first XBB and then eventually became XBB1.5. And you said then someone was infected with two variants at once. Is that a common thing then? Increasingly, unfortunately, it's not very uncommon because there is so much Omicron around. There are there have been multiple waves since Omicron first emerged over a year ago. And that means that people have the opportunity to be exposed to potentially more than one Omicron variant. So co-infections of two different variants at the same time are not uncommon.

And we have seen other recombinants emerge in this way. In fact, BA3 is a recombinant virus itself of two different Omicron sublineages. Wow. And if you were infected like that, would it feel any different, your experience of COVID? Probably not, because these are still both BA2 derivatives. So they do share many of the same mutations relative to other Omicron lineages or other variants. So you probably wouldn't even know then, really. You probably wouldn't even know. It would just feel like you had Omicron. And I've heard this variant is called the Kraken. Why is that? Why are we calling it that?

Well, we are actually not calling it that. And by we, in this case, I mean virologists who actually study SARS coronavirus 2. Some people have decided to start nicknaming many of these subvariants. Their argument is that it helps with communicating to the public about these variants and some of their different properties. But one of the reasons why a lot of virologists actually aren't using this terminology is really twofold. First of all, the XBB1.5 name actually does mean something. It refers, again, to the virus's evolutionary history. And then there's the other reason, and that is that maiming subvariants after these mythological monsters effectively really implies something about them that may not be true. And that is that this is somehow worse than other Omicron subvariants that may be circulating, may not have a nickname.

And I don't think we actually have the data to suggest that this is going to be any worse. We heard the same sort of things about other variants, including, I believe, Hippogriff was XBB. And over the summer, it was predicted to be the worst variant ever. And it did not become dominant in the places that it was circulating. And I fear that by saying, oh, this variant is so much worse than this other one, it really obscures the message that it was circulating. And I fear that by saying, oh, this variant is so much worse than this other one, it really obscures the message that we should be taking the same steps for all of these different viruses. Yeah, fair point there. Of course, one of the reasons why we are talking about this variant, though, is because it is spreading

really rapidly, particularly in the U.S. And I want to ask you about this, Angie. Do we know how quickly is it actually spreading these days? So this is really challenging because of both data collection gaps over the holidays, as well as the fact that we're just not collecting as much data as we used to. There are fewer molecular tests being performed. There are fewer sequences being obtained. Many people, if they get sick and they don't have to actually go to the hospital or seek medical treatment, will either not test or use a rapid test at home, which doesn't get reported and doesn't distinguish which variant is causing the infection.

So it can be very tricky. And that's kind of what we saw in the U.S. But in a period of about a week, week and a half, two weeks, we saw the cases of XBV1.5 go from about 5 to 10 percent of all of the COVID cases that were being detected to anywhere between 25 and 40 percent. So more than doubling there. More than doubling. Yes. And that really does indicate that XMV1.5 may be outcompeting the other variants that are circulating in the population and causing a disproportionately higher number of infections. Now, whether we're going to see that in Canada or not, it's still early days and it's very difficult to tell. But that's certainly a possibility. And that's something that I and all of my colleagues are keeping a close eye on. How many cases do we have in Canada then? So as of this week, we have fewer than 50 cases. It's in the low 40s. Our detections,

I should say, because that can include wastewater detections. It could be many more, however. And again, that's because it was over the holidays, so there can be a lag in collecting some of that data and getting some of those sequences. It also is affected by people not necessarily going to get a molecular test, a PCR test, which is then used for sequencing. People, if they use rapid tests at home or if they don't test, those cases will essentially be lost to the data. So it could be more. It almost certainly is more than the 40 some cases that have been detected. But right now, because it is still such a small number, we can't really say for sure how many cases there actually are in Canada. We'll be back in a moment. Let's get into a bit of the biology if we can here, Angie, because we talked,

you talked about mutations and different variants and how those those can change. So what mutations specifically does this variant have that are maybe making it spread so quickly? Yeah, so this is a really great question. And I think this is one of the areas where being alarmist has really not served us well, because XBB1.5 has a single mutation in its receptor binding domain of the spike protein that distinguishes it from XBB. So that interaction of the spike protein receptor binding domain allows the virus to actually get into the cell and cause an infection. If you don't have that interaction, the virus can't get in, the virus doesn't cause an infection. So essentially, does this mutation, I guess,

make it like stick better to our cells? Is that a way of understanding it? So that's possible. And some early studies have indicated that that might be exactly what this mutation is doing. It makes it actually more capable of binding that receptor and getting into the cell. So all of our vaccines are designed against the spike protein. And that's because when antibodies are directed at the spike protein, And that's because when antibodies are directed at the spike protein, they can block that interaction with the receptor and render the virus effectively non-infectious. So having a mutation there means that some of the antibodies that have been elicited by the vaccines aren't necessarily going to be neutralizing because they aren't going to be targeting the same receptor binding

domain effectively. So essentially, this variant then could evade our immunity in a better way, it sounds like. That's right. But the caveat there is that this is a single mutation. Now, XBB itself already has other mutations relative to older, to its ancestors in the receptor binding domain, which is one reason why Omicron in general is more immune evasive than any variants that we've seen before. But relative to XBB, XBB1.5 is not that different. Now, that's not to say that this might not have an impact. It could explain why this is more transmissible, but it doesn't necessarily indicate that it's going to completely evade immunity. And in fact, there is some data suggesting that especially the bivalent boosters

do offer pretty significant neutralizing antibody protection against XBB. So XBB 1.5 should not be that different. Okay. Okay. So it looks like potentially more transmissible. We're also hearing though that it might be less virulent. Can you talk to that? So all of the Omicron variants can be extremely virulent. They can cause extremely severe disease, particularly in people who are vulnerable. But we are not seeing in the Canadian population where most people have at least had the primary series of the vaccine and a whole bunch of other people have had Omicron as well. We are not seeing the same proportion of people getting really, really sick and going to the hospital and dying. Now, that's not to say that this virus is inherently milder. It's to say that the population actually has a significant level of immunity against all of the Omicron subvariants, and that's mitigating their impact a

bit. The problem, a big problem with Omicron is not necessarily its inherent virulence. It's the fact that it's so transmissible and people are not necessarily up to date on their boosters and we have fewer precautions that people are taking. And so it's infecting a lot of people. And any time you have a whole lot of people infected, even if the proportion of those people that get sick, very sick, is lower, that still translates to an absolute number of people getting very sick that's still very high. I'm really glad you brought this up because I was wondering about the numbers here. We were seeing stuff about how 2022, the latest year, was actually the deadliest year for COVID so far in Canada,

just over 19,000 deaths in 2022. Compare that to 14,000 in 2021 and 15,000 in 2020. Is that what's going on here then? It's the increase in deaths is because of the sheer amount of people who are infected? That's exactly right. If you have a lot of people getting infected, you're going to have, even if it's a lower overall percentage, you're still going to have a lot of actual individual people showing up at the hospital, getting really sick and dying of covid, unfortunately. And and this really explains to me the fact that that we have seen more deaths as mask mandates have been lifted. Travel restrictions have been lifted. Mandatory testing have been lifted, travel restrictions have been lifted, mandatory testing has been lifted. It's harder for people to get access to tests in many places. And there's also

no policies that have made it easier for people to do things like stay home when sick, since there's not universal sick leave. All of those things contribute to more widespread transmission. That results in overall a larger number of people getting sick and still a larger number of people, even though it's a smaller relative proportion, ending up in the hospital and unfortunately dying. And because this subvariant is more transmissible, potentially can invade immunity better as well. Are people likely to be reinfected with COVID now? So certainly, if people aren't taking precautions, they are more likely to be infected with COVID. And as I mentioned briefly before, there is some preliminary data that suggests the

bivalent boosters can really boost neutralizing antibodies specifically that work against XBB. About a month ago, a study came out from the CDC in the U.S. showing that a BA.5 bivalent booster could reduce your risk of symptomatic COVID. So that means essentially getting infected with COVID by about 30 percent. Now, the protection they provide against severe disease is incredibly high, over 50%. So people really do need to think about getting a bivalent booster because the bivalent boosters are going to, whether it's a BA1 or a BA5 bivalent booster, they are going to increase immunity specifically to Omicron and to all of the variants and sub-variants in the Omicron family. Now, in Canada, a majority of people have not yet had a bivalent booster.

So it is really important, I think, for us to encourage people, if you don't do anything else, go out and make sure that you're up to date on your booster shots, including a bivalent, if you are eligible to get one. And that means if it's been four months since your last booster or your last COVID infection. In addition to that, people really should consider applying other measures as well. So wearing a mask in public spaces, avoiding crowded situations, improving ventilation or using air purifiers or air filters if you can, using rapid tests to determine if you're infected and then self-isolating if you are, and staying home if you're sick, if you are able to do so again. I think that adding some of those additional mitigation measures on top of an

up-to-date vaccination regimen will significantly reduce transmission risk, both in the population as well as for you as an individual. Just before I let you go here, Angie, given everything that we've talked about here, everything that we're seeing with this new subvariant, what do you think we're in for in the coming months? I mean, I think we're in for more waves of COVID, unfortunately. And that's not necessarily because of XBV 1.5. That's just due to the fact that we aren't doing a good enough job to reduce respiratory virus transmission in general. And we haven't done a good enough job making sure that people are up to date on their boosters. I'd argue that we really need to be focused too on policy measures and investments that could

mitigate it further. So developing better vaccines, vaccines that would be covering all potential variants really robustly, vaccines that could induce potentially sterilizing immunity and reduce infections more. Also, things like infrastructure upgrades, like improving indoor air quality, improving ventilation, improving air filtration in public spaces. You know, that doesn't happen overnight, and that requires a significant financial investment. But that's something that long term would really, I think, pay off big time because that would reduce transmission of all respiratory viruses. So people really do need, I think, to get this message that we're going to be living with SARS coronavirus 2 for a long time, potentially our entire lifetimes. This virus isn't going away. It's entrenched in the human

population. It can infect other animal species, which can create reservoirs for it. We're not going to eradicate it. And certainly with the policies that we have in most other countries in the world have right now, we're not even going to eliminate it. So our goal needs to be making sure that it has as minimal of an impact as possible on us as individuals, on our communities, and on our healthcare systems.

And I think that we really can get there, but we do need to do a better job of making people aware of what they can do to reduce their own risk. Angie, thank you so much for taking the time to help us understand this. Oh, it's my pleasure. Thanks so much for having me. That's it for today. I'm Mainika Raman-Wilms. Our producers are Madeline White, Cheryl Sutherland, and Rachel Levy-McLaughlin.

David Crosby edits the show. Kasia Mihailovic is our senior producer, and Angela Pichenza is our executive editor. Thanks so much for listening, and I'll talk to you tomorrow.