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The Bubonic Plague Is Older Than You Think - Video học tiếng Anh
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The Bubonic Plague Is Older Than You Think
The Bubonic Plague Is Older Than You Think
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0:00
We’ve got a problem.
0:01
A big problem that’s been bothering humans for a really long time.
0:06
You might even say that this problem has been… plaguing us.
0:10
Yeah, it’s the plague.
0:11
More specifically the bubonic plague,
0:13
of “Black Death” fame, during the Middle Ages.
0:16
But that was neither the first nor the last time it afflicted us.
0:20
In fact, people are still getting plague to this very day.
0:23
So let’s explore the ancient history of
0:25
humanity’s most infamous disease.
0:30
[♪INTRO]
0:31
Scientists discovered the cause of bubonic plague back in 1894.
0:36
It wasn’t the wrath of god; it wasn’t an
0:38
astrological misalignment of the planets.
0:40
It’s a type of bacteria called Yersinia pestis,
0:44
or Y. pestis if you’re in a hurry.
0:46
You’ll notice that 1894 is several
0:49
hundred years after Europe’s medieval era.
0:52
So before then, people also used the term “plague” pretty willy-nilly,
0:56
to describe both globe-spanning pandemics and personal annoyances.
1:00
But these days, “plague” means Y. pestis, which comes with fever,
1:05
chills, pain in your limbs, and…
1:07
when the bacteria infect your lymph nodes…
1:09
the infamous lumps called buboes.
1:11
You can also say buboes, and therefore the bubonic plague.
1:16
Which I think sounds a little more appropriate, because ew.
1:25
And that’s right. Y. pestis actually causes different plagues,
1:29
depending on where it infects you. In addition to bubonic plague,
1:33
there’s also septicemic plague, which infects your blood
1:36
and can lead to blackened tissues from gangrene,
1:39
and pneumonic plague which gets into your lungs.
1:42
For the record, the bubonic variety is
1:44
actually the most survivable of the three.
1:46
Despite knowing quite a lot about plague,
1:49
for quite a long time, scientists are still finding
1:52
out new information about this very old disease.
1:55
In 2021, one team found evidence for the oldest known case of plague:
2:00
a man who lived in present-day Latvia more than 5000 years ago.
2:03
The researchers analyzed the ancient Y. pestis DNA
2:06
from the man’s remains, and they concluded
2:08
the strain probably wasn’t super contagious.
2:11
Nevertheless, the man probably got infected by a rodent bite,
2:15
had septicemic plague, and died a few days later.
2:17
Then, in 2023, another research team tracked
2:20
the plague’s progress to Britain, 4000 years ago.
2:24
They found Y. pestis DNA in the teeth of people buried at two
2:27
different sites on the island, about a four and a half hour drive apart.
2:30
This specific strain of plague is called
2:32
the Late Neolithic Bronze Age lineage,
2:34
or LNBA for short. Between roughly 2900 to 500 BCE,
2:39
it appeared all over Eurasia, from Mongolia to Western Europe.
2:43
But it’s a bit unclear how it managed to do that.
2:46
This seems to be a few centuries before Y. pestis
2:49
developed an adaptation that vastly improved
2:52
its ability to hitch a ride and spread via flea bites.
2:55
That adaptation was a brand new gene, called ymt,
2:59
which one lucky Y. pestis cell acquired from an interaction with some
3:03
other microbe’s DNA, and then passed it on to all its descendants.
3:06
ymt helps the bacteria survive in a flea’s digestive tract.
3:10
While Y. pestis was still infectious without it,
3:13
it wasn’t infecting people directly through flea bites as much.
3:16
A different study, published in 2025, may help explain things.
3:20
Because researchers found some LNBA-era plague DNA
3:24
in the bones of a sheep from the modern-day
3:26
Russian region of the Eurasian steppes.
3:28
This was a domesticated sheep, and its variety of plague
3:31
had a close genetic match to samples from infected humans
3:35
who lived in the same region around the same time.
3:38
It’s likely this sheep came into contact with an infected wild animal.
3:42
The plague then passed from the sheep to humans
3:44
when the sheep was being handled and consumed.
3:46
So Y. pestis may have originally infected most humans via
3:50
their livestock. But eventually, fleas got their time to shine.
3:54
Researchers haven’t found the genetic mutation required for flea
3:58
transmission in any Y. pestis samples more than 3,700 years old,
4:03
but it’s extremely common in those younger than 3,000 years.
4:06
But be it a sheep, or be it a flea, a spillover from
4:10
animals to humans is a good way to start a pandemic.
4:13
And in 541 CE, we got the start of our first proper plague pandemic.
4:18
The Plague of Justinian, named after the Byzantine emperor
4:21
at the time, is often considered to be both the first plague
4:24
pandemic and the first recorded pandemic, ever.
4:28
It probably started around Egypt and the Mediterranean,
4:30
and it killed anywhere between 25 and 100 million people.
4:35
Contemporary accounts of the symptoms led scientists
4:38
to speculate this pandemic was caused by Yersinia pestis.
4:42
They also uncovered contemporary samples of Y. pestis,
4:45
but some researchers felt these weren’t close enough
4:47
to the outbreak’s supposed epicenter to be definitive proof.
4:51
It wasn’t until 2025, and the bacterial DNA hiding
4:55
in eight teeth unearthed from a mass grave in Jordan,
4:58
that they decided, “Yeah; it was definitely plague plague, guys.”
5:03
Now, the Plague of Justinian was not a one-and-done incident.
5:07
The initial round of outbreaks lasted until about 549 CE,
5:12
but the particular strain of Y. pestis behind
5:14
it stuck around for two more centuries.
5:17
It triggered another 18 or so waves of plague outbreaks.
5:21
Then, it disappeared.
5:22
This seems to be a common pattern for plague.
5:24
Any given strain tends to die out after just a few centuries,
5:28
most likely due to anyone with a natural genetic resistance
5:32
to the disease surviving and passing that onto their offspring.
5:35
Over time, this would increase the population’s
5:38
overall resistance, reducing disease spread.
5:42
But as history knows, Yersinia pestis
5:45
wasn’t even close to being done with us.
5:47
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5:49
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7:00
In 1346, the Black Death kicked off
7:03
humanity’s second plague pandemic.
7:05
Scientists have tried to track down
7:07
the origins of the Black Death for centuries.
7:10
The stories used to go that it started in China,
7:12
and quickly spread down the Silk Road to Europe.
7:15
It turns out those stories were just that: stories,
7:18
originating from a 14th century poet who wrote about a fictional
7:22
trickster spreading the plague from China to the Mediterranean.
7:25
Even though this particular tale was never meant to be taken as fact,
7:29
its author did later write historical pieces.
7:32
People apparently mistook his trickster tale for history as well.
7:36
So if you’ve ever felt bad because a movie
7:38
taught you something very wrong about history,
7:40
take comfort that one of your ancestors
7:43
would experience something similar.
7:45
Fortunately, we now have modern
7:47
tools to analyze ancient Y. pestis DNA.
7:50
And by analyzing how mutations accumulate
7:52
over time and space–
7:54
and the power of statistics–
7:56
researchers can identify where certain genomes are most likely from.
8:00
In a study in 2022, researchers collected
8:03
ancient DNA from 14th century plague victims.
8:06
They sequenced the plague genomes that they found in the bodies,
8:10
and compared those to other genomes of known geographical location.
8:13
Turns out, this strain of plague probably
8:16
got its start in Central Asia. Not China.
8:19
Even though the Black Death only lasted a handful of years,
8:22
it managed to wipe out at least one third of Europe’s population.
8:26
So many people died that the remaining population passed along
8:30
a very particular set of genes that protected their descendants.
8:33
Which is great, although not always.
8:36
Some versions of these plague-protecting genes are also
8:39
associated with an increased prevalence of autoimmune disorders.
8:43
So if you’ve got Crohn’s Disease and a European ancestor,
8:47
congrats on probably being a direct descendant of a plague survivor!
8:51
Now, I did say the Black Death kicked off the second plague pandemic.
8:55
In fact, that pandemic didn’t end until the 1800s.
8:59
And genetic evidence reveals Y. pestis probably
9:02
re-entered Europe multiple times over the centuries.
9:05
In which case, there was probably a reservoir of this specific
9:08
strain outside Europe, likely involving some kind of rodent.
9:12
A reservoir is a niche in the environment where a disease
9:15
can hang out, multiply, and continue existing in the wild.
9:19
They’re super important for understanding the existence and
9:22
spread of plague. because it’s not just the fleas that
9:25
we have to worry about. It’s also the animals that the fleas feast on.
9:29
With the movement of both people and animals,
9:32
the Black Death strain kept circulating throughout Western Europe.
9:35
Along the way, natural selection did its thing,
9:38
and one Y. Pestis strain split into two major lineages.
9:42
One of them is the evolutionary ancestor
9:44
to all modern strains of plague…
9:46
which we’ll get to in a moment.
9:48
The other lineage died out by the 1800s.
9:51
The exact reasons for this extinction aren’t totally clear.
9:54
Some scientists think this branch of the Y. pestis family tree
9:58
evolved to hang out in an animal reservoir that no longer exists.
10:01
Another hypothesis has to do with
10:03
the genetics of the plague strains themselves.
10:05
In both of the pandemics we’ve talked about so far,
10:08
the Y. pestis strains evolved to be less deadly after about 100 years.
10:13
According to a paper published in 2025, this decrease in
10:16
mortality is associated with fewer copies of a gene called pla.
10:20
The pla gene helps Y. pestis fly under your immune
10:23
system’s radar until it reaches your lymph nodes.
10:27
So if you’re Y. pestis, it sounds pretty nifty to have as
10:30
many copies of pla as possible in your DNA, right?
10:33
Well, when the plague strain has more copies of pla,
10:36
it’s more deadly more quickly, so the host doesn’t
10:39
have as much time to spread the disease to others.
10:42
Meanwhile, when there are fewer copies of pla, the host lives longer
10:46
and the disease is less severe, so it can pass on to more hosts.
10:50
In other words, there’s an evolutionary advantage
10:52
for the bacteria to stop having so much pla.
10:56
But not everyone agrees with this pla hypothesis, so the jury’s still out.
11:00
FYI, the fact checker for this script noted that we missed out on
11:00
saying this hypothesis was pla-sible. Thanks, Angela.
11:00
As for the Black Death lineage that kept on cooking, in the late 19th
11:04
century, a third plague pandemic broke out in Yunnan, China.
11:07
It spread all across Asia, then globally until the 1950s,
11:12
causing 12 million deaths in a century.
11:15
Thankfully, we are not currently in the middle of a plague pandemic…
11:19
as of the day we’re filming, at least.
11:21
But that doesn’t mean humanity has had its last one.
11:24
The plague is definitely still around in the 21st century.
11:27
We’ve just traded our plague doctor masks for N95s.
11:31
Today, Y. pestis is most commonly found in Madagascar,
11:34
the Democratic Republic of the Congo, and Peru.
11:37
Thankfully, even though the plague comes and goes in those areas,
11:40
the number of infections tend to stay pretty low:
11:43
hovering under 50 cases, each.
11:45
The United States sees about seven plague diagnoses per year,
11:49
and extremely low death rates.
11:51
But in July 2025, a person from Arizona died of pneumonic plague.
11:56
While the official report didn’t share how this person got the plague
11:59
in the first place, animal reservoirs for Y. pestis in the US tend
12:03
to be rodents, especially prairie dogs, squirrels, and chipmunks.
12:06
I don’t care if they’re cute, DO NOT TOUCH THE WILD ANIMALS!
12:11
So, what tools do we have to fight and prevent plague?
12:14
If you’ve ever seen Monty Python and the Holy Grail,
12:17
the monks going around bashing themselves in the head
12:19
are probably loosely based off of a real-life
12:22
anti-plague belief during the Black Death.
12:25
People thought that the plague was the wrath of God, and hitting
12:28
themselves was a way to punish themselves to earn forgiveness.
12:31
Fortunately, we have more effective ways of dealing with plague.
12:35
Masks do prevent transmission,
12:37
at least the human-to-human kind,
12:39
and we have plenty of antibiotics that are
12:41
effective if they’re given early enough.
12:43
Unfortunately, some strains of Y. pestis
12:45
have already developed resistance to antibiotics,
12:48
but that doesn’t seem to be an
12:50
immediate concern to health professionals.
12:52
They’re focusing on other bacteria that are
12:55
already showing anti bionic resistance at the moment.
12:57
Meanwhile, we don’t have many vaccine options available,
13:01
but scientists are working on it. In this case,
13:03
it tends to be a challenge of making a vaccine that works
13:06
well at an affordable price for mass manufacturing.
13:09
They’d better keep at it, though,
13:10
because thanks to the existing environmental reservoirs,
13:13
there is a very real risk of a fourth plague pandemic.
13:16
And I’m not just talking about the prairie dogs,
13:19
or a select group of flea-carrying rodents.
13:21
Over the years, scientists have learned Y. pestis can
13:24
chill out in human body lice, soil, and amoebas in water!
13:28
And for those of you with feline friends,
13:30
I should mention cats are susceptible to severe cases of plague.
13:34
So if your cat keeps leaving you decapitated presents,
13:37
maybe keep an eye out.
13:39
It looks like this bacteria might plague us for a while longer.
13:47
[♪OUTRO]
