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Also, this episode was filmed on March 9th 2021. For our most up to date episodes regarding the
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Lately, we’ve been talking a lot about new variants of SARS-CoV-2 that arise through
mutation — the small genetic changes that can accumulate over time.
But in early February, scientists in the US said
they’d found a different type of variant — a recombinant virus.
That’s a hybrid of sorts with chunks of genetic information from two variants that came together
in a host through a process called recombination.
And while this development is concerning, it’s actually not surprising, given what we already
knew about coronaviruses.
Plus, there’s a hopeful side to all this. According to other recent findings, it seems
that the habit for recombination these viruses have may also be a vulnerability that we can use
against them.
Now, this recombinant virus is a preliminary finding,
and there’s zero evidence that it’s circulating in the population.
It came up in a sample from one patient, and it could even be an artefact that occurred after the
sample was taken.
But it’s notable because the scientist who found it thinks it could be the
most compelling evidence to date of a recombination event happening “in the wild.”
And, well, a lot of people are talking about it.
But again, it’s not a huge surprise.
Scientists have been looking for recombinant viruses throughout this pandemic. Like,
some of the first concerns were published in March 2020.
But, while there’s been the occasional paper, the general consensus is that there just hasn’t
been enough evidence for researchers to agree these recombinations were happening.
One reason they’ve been monitoring this so closely
is because of what they’ve seen with other coronaviruses that infect livestock.
Recombination in a couple of these viruses has led to big changes that let them “escape”
vaccines. That’s a term that scientists use when a vaccine isn’t as effective
against a new variant.
At this point, there’s no reason to think we have a vaccine escapee.
Still, this specific situation is something researchers are keeping
an eye on — especially because of who the parent viruses seem to be.
One is the B.1.1.7 variant first seen in the UK,
which appears to be more transmissible than other variants.
The other is B.1.429, a variant first seen in California,
which seems to be better at evading immune defenses.
And, according to this preliminary report, the new one, or offspring if you will,
has key genetic features that could mean it’s both of those things!
But in practice, we don’t yet know anything about how it would behave,
because no one ran tests on it.
As for how this virus came to exist?
Well, this type of recombination can happen when someone is infected with two different SARS-CoV-2
variants at once, because coronaviruses do something a bit weird while they’re reproducing.
You see, inside an infected cell, specific viral proteins move along the length of the
virus’s RNA genome to make copies of it, some of which later get wrapped up and exported as new virus particles.
But, the proteins usually don’t make these copies all in one go. They hop on and hop off.
So, if there are two different viral genomes floating around,
they can start copying one genome, and then hop over to the other one when they continue.
That can lead to new viruses with chunks of genetic information from both variants.
But the real takeaway here is that researchers have been expecting this sort of thing!
Because we’ve known for a long time that recombinatio n is common in coronaviruses.
In fact, most scientists think it was a recombination event that gave
SARS-CoV-2 the ability to infect human cells in the first place.
In a bat — or, more likely, some other animal — a bat coronavirus
met up with another coronavirus, did this genome-mixing thing,
and ended up producing a virus that happened to be really good at infecting us.
And it’s actually pretty likely that recombination has been occurring all along.
It’s just that scientists don’t sequence the genome from every sample, or even most,
so there could be things happening that don’t get recorded. And, when variants
don’t have a lot of genetic differences, recombination events may be harder to detect.
There's also new evidence that recombination in coronaviruses isn't just common;
it's a fundamental part of their life cycle.
In a study published in January, researchers infected cells in the lab with coronaviruses
and looked closely at all the genome copies they made.
And they saw evidence for a lot of that jumping on and off that leads to recombination.
That led them to conclude that it’s an important part of the viruses’ everyday existence.
Now, the idea that coronaviruses are especially prone to mixing genomes
might sound like a bad thing, given these mixes can carry the worst traits of their parents.
But the process can just as easily
mash up less useful traits to create wimpier variants — you just don’t hear about those.
And, fortunately, it looks like it’s still pretty
rare for someone to be infected with two variants at once.
Plus, prevention measures like distancing, hand washing, masking, and vaccination
should make it even less likely for that to happen.
But also: the encouraging news here is that what the researchers saw suggests recombination
is essential to coronaviruses.
The jumping on and off while copying seems to be a key part of how they
make the instructions that tell the cell they’re infecting to build new viruses.
And if that’s the case, then the thing that
makes these viruses seem so scary may also be a giant weak point.
We may be able to develop drugs that specifically
target the proteins involved in recombination to mess up their ability to replicate period.
It’s another example of how, the more we learn about how these viruses work,
the more ideas we get for stopping them.
You can also take some comfort in knowing that scientists are out there monitoring
the situation, which will leave us better equipped to deal with whatever
happens next.
There’s a lot we want and need to know about recombinant viruses. But if you
need a break from learning all this need-to-know stuff,
you might enjoy a brand-new podcast called Things You Don’t Need to Know.
It’s hosted by Ari Cagan, an 8th grade dropout who’s spent his life since learning
all sorts of fascinating if not so everyday-relevant things.
And now, by listening to his weekly podcast, you can also learn these
new and unconventional things! Like, how to defuse a bomb, or invent a new food.
And hey, even if you never use the skill in your daily life,
it’s sure to spark some fun conversations!
You can find it by searching for Things You Don’t Need to Know
on the podcast platform of your choice or clicking the link in the description.
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