All language subtitles for The.UnXplained.S03E10.WEB.h264-BAE_[English] (SUBRIP)

William shatner:
From the plagues of egypt

to the black death,

smallpox,

cholera,

and the spanish flu,

humans have repeatedly faced
contagious diseases

that have the power to change
the course of history.

We like to think
that modern medicine

can protect us against
almost everything, but...

Is that really true?

Or are we destined
to face a future

of ever more potent illnesses

that attack without warning

and can bring civilization
to its knees?

Well...

(sucks air through teeth)

...That is what
we'll try and find out.

♪ ♪

shatner:
News reports surface that a new,

highly contagious disease first
discovered in wuhan, china,

is spreading like wildfire.

In a matter of weeks,
the lethal virus--

known as "coronavirus"
or "covid-19"--

sweeps the globe.

On March 11,

as the number
of infections and deaths

continue to climb,

the world health organization
declares

that the outbreak has become
a worldwide pandemic.

Raj dasgupta:
What separates, clinically,

coronavirus from other
common viruses such as influenza

is that it knows
how to hide itself.

It has what we call a period
where you could be asymptomatic.

That means without symptoms.

That's a chance to pass
that virus to other people,

keeping the disease going on
and spreading.

Most of the time, when you wait
for these symptoms,

you've already missed it.

Shatner:
In the wake
of the harrowing effects

of the coronavirus outbreak,

scientists have been compelled
to reexamine

the nature
of viruses themselves.

Viruses are very mysterious,

because you can't see them.

You need
a very powerful microscope

to be able to see them.

And we didn't even know
that they were around

until relatively recently.

Kirsten fisher:
A virus is essentially a bit
of nucleic acid,

either dna or rna,

encapsulated
in some sort of coating. Right?

So it needs to-- it needs
to get into another organism

and then essentially hijack that
organism's cellular machinery

to make more copies of itself.

Dasgupta:
It needs to

actually take over
another living cell.

And whether that's
the living cell of a human,

animal,

plant or even a bacteria,

it needs that.

It's making more
and more viruses

till that cell
is not needed anymore.

Fisher:
A virus relies on either

direct transmission
through sneezing or coughing

or touching, um,
a viral particle

from a person who's expelled it.

Or they rely on a mosquito
or some other organism

to be transmitted
between people.

And so the density of people

will facilitate
quicker spread of viruses,

especially if it's, um,
relatively contagious

and-and easy to-to transfer
from one person to another.

Shatner:
According to experts,

the origins of many viruses

remain shrouded in mystery.

Dasgupta:
It's so difficult

to determine
the origin of viruses because,

when you want to study
that virus,

you have to separate what is the
natural history of that cell.

So one of the important things

that epidemiologists
are looking at right now is,

what did we learn from the past?

What should we be looking at?

Where should we be looking?

Some of the earliest records
of plagues

are found in ancient india,

china, the middle east,

and they talk
about plagues occurring

before the very first
civilization,

around 3200 bc.

Shatner:
Throughout human history,

there have been accounts
of devastating afflictions

that defied understanding
at the time they happened.

But perhaps a closer examination
of these plagues

will provide some lessons
about infectious diseases

and how they begin.

(gull calling)

emperor justinian
sits atop a powerful throne.

But lurking in the shadows
is a hidden enemy

about to consume his kingdom.

A plague

started by a bacteria

comes out of the east

and infects.

This simple bacteria

ended up killing

almost one half the population
of the entire old empire.

With that type of death toll,

the economic
and social ramifications

were catastrophic.

Everything
that justinian had tried

was now collapsing.

His military collapsed,
his economy collapsed.

And everything
that he tried to do

was of no avail.

(coughing)

fisher:
Justinian plague
is caused by a bacterium,

yersinia pestis.

It can either enter humans
directly, um, through--

from saliva or-or coughing.

It usually manifests itself

in terms of swelling
of the lymph nodes.

The skin turns black
and basically dies.

And then there's
a progression of fever

and chills and eventual death.

Tzadok:
As justinian's empire
was collapsing and breaking

and his military strength
was waning--

because the science of medicine
in those days

was far more primitive
than we have today.

People cry out, "why?

Why is this happening?"

shatner:
The plague of justinian,
as it became known,

ultimately killed
an estimated 50 million people.

The vast byzantine empire
was crippled

not by an invading army

but by an enemy they could
not see and did not understand.

At the time,

since the existence
of bacteria and viruses

had not yet been discovered,

many believed that the invisible
force that caused the plague

was god himself.

It was a belief
that was widely accepted,

because people would read
in the bible

about how pestilence
from the past

had been created
by the hand of god.

Whenever humanity is infected

by something greater
and beyond human understanding,

it has always been
psychologically understood

to be an expression
of the wrath of god.

We have in the book of exodus

the famous ten plagues of egypt.

Moses had come back
after seeing god on the mountain

to free the hebrews
from slavery.

He went before the pharaoh
and asked to let his people go.

Of course, the pharaoh said no.

Therefore, the hebrew god sent a
number of plagues through egypt.

Tzadok:
The bible stories are clear.

The order of the plagues are
well-documented in the bible.

We know, of course,

that there was the turning
of the nile into blood.

There were the frogs,
the lice,

the pestilence and, of course,

the great plagues
of the three days of darkness

and, of course,
the death of the firstborn.

Bidmead:
The biblical writer
who is writing what happens

and is inspired by god

does say that the plague stopped

after the hebrews
were finally free.

So, perhaps there was some
divine intervention from god.

But we'll never know,

because miracles
are very difficult to prove.

Shatner:
Was there a higher power
involved

that both started and ended
the plagues of egypt

and the plague of justinian?

Perhaps more clues as to what
causes devastating plagues

can be found by examining
the disease responsible

for claiming more lives
than any other.

Officials from the california
odepartment of public health

alert residents
that a woman has tested positive

for a dangerous
and quite unexpected disease.

The bubonic plague,

otherwise known
as the black death.

Dasgupta:
Does the bubonic plague
still exist?

The answer is... Yes.

And it's amazing

how, many centuries later,

you could say this
with a calm voice.

What is the difference?

The answer is antibiotics.

We know that if you have
symptoms early

that antibiotics
can save your life.

Fisher:
While it's not as prevalent
anymore,

the plague is certainly still
in circulation.

In the united states, right,
in more rural areas,

where people come into contact
with-with rodents

that might be infected with it,

it's still known to, like,
crop up here and there.

The worst case of the bubonic
plague that there was

was known as the black death,

in the middle of the 1300s.

And that wiped out

60% of all
of europe's population.

Shatner:
12 trade ships arrive

from the black sea

and drift into the port
of messina to unload freight.

As dockworkers

approach the vessels,

they discover
a disturbing scene.

Dasgupta:
The port master goes on board

to see the crew,
and, to their surprise,

it was almost like
there were zombies on the ship.

Gangrene fingers.

Big boils.

And if I saw

a crew that had black fingers

and boils, let's be honest:

It sounds like
a zombie apocalypse.

The black death
seemed to have been introduced

via the silk road,

which is a major trading route

in the early medieval period
from central asia

where the bubonic plague
regularly pops up.

Europe seems to have been
largely unprepared

for this devastating event.

This is in the 1300s.

It went for quite a few years,

and whole villages and areas
were wiped out.

And like many plagues, uh,
people wondered why.

Dasgupta:
These cities
would get the plague,

and no one knew why.

And then we always have
the advantage

of looking back on history
and tracing.

Historians could look back
and say, "wait a minute.

"all the cities with ports

"that do a lot of trading
were infected.

And what were going
to all these ports? Ships."

phillips:
The black death

was spread by fleas
that lived on rats.

And wherever these rats went,
the fleas went,

and they bit people.
That's what made them ill.

Christine colby:
The flea would actually
vomit the bacteria

onto the person's skin
while biting them.

The disease spreads
to the body's lymph nodes

and causes buboes,

which are infected sores

which get to be
about the size of an egg.

And they eventually burst
and expel bloody pus.

The body goes through

such horrific
and gruesome transformations

that from the time you contract
the bubonic plague until death

can sometimes only be
a matter of days.

Shatner:
During the middle ages,
many believed

that demons were responsible
for the black death.

-(coughs)
-and people who were deemed

to be wicked or unworthy

were punished

in hopes
of driving the demons away.

Tzadok:
Many people believed

that the source of this plague

was caused by evil spirits,

witchcraft and the like.

The powers of the occult.

And this led many people

to seek out
any type of expressions

of the occult,
witchcraft and the like...

...And to root it out

in the attempt to placate god.

(screams)

shatner:
Some were so convinced
that the black death

was a scourge
brought by evil spirits,

they were willing
to scourge themselves.

One common occurrence during
the time of the black death

was to see, uh, people that were
called flagellants, which...

They were under the belief
that they were being punished

by god for their sins,
so they would publicly atone,

and they would March
through the town square,

flogging themselves
in the name of god.

(groaning)

thompson:
This flagellation movement
really exploded.

Whole towns
flagellating themselves.

Those that didn't were accused
of being with the devil.

Phillips:
Something else that came
from the black death was

the practice
of selling holy relics.

When the black death
was decimating europe,

the church were saying,

"come to us,

and we can cure you."

the bones of a saint

or something that had
once belonged to a saint

kept in these churches.
They were called relics.

And people believed
that if they went there

or close to such relics,

prayed, that god may intervene

and protect them
from the plague.

Now, they weren't curing anyone,

but people were still flocking
to the churches

just on the hope
that they could be cured.

Dasgupta:
So, when we talk
about the many lives

that were lost
during the black death,

I think about a horror movie.

Shatner:
Historians estimate
that the black death

wiped out anywhere
from 50 to 200 million people,

at least a third
of europe's population.

So it's little wonder

that most people thought
that something so destructive

must have been some kind
of punishment from god.

But today, we have
a much different understanding

of this disease.

Gronvall:
We call it the black death,

but it's-it's a bacteria
called yersinia pestis.

But it's not as dangerous
as it was then.

Now we have antibiotics.

We can detect it.

You know, you can treat it.

In any case,

yersinia pestis
is still around today,

which begs the question,

is it possible

to actually kill off
a fatal disease

once and for all?

Perhaps the answer can be found

by examining a deadly plague

that, believe it or not,

has been infecting humankind

for more than 10,000 years.

Shatner:
The valley of mexico.

Spanish conquistadors
led by hernán cortés

arrive at tenochtitlán,
the capital of the aztec empire,

bearing dreams of conquest

and an insatiable desire
for gold.

But they also brought with them
a lethal, infectious disease.

Thompson:
Smallpox is introduced

into the americas
very dramatically

at a specific point in time

and alongside
the european invasion.

This is a tremendous
sort of clash of civilizations,

the likes of which
the world had never seen before

and will never see again.

The single most deciding factor

as to why native american
civilizations fell so rapidly

was the introduction
of smallpox.

Fisher:
So, smallpox is a virus.

It causes these
sort of irregularly spaced,

pustule-y skin lesions

and had a devastating effect

on-on native americans,
um, in the new world.

Gronvall:
In europe, most people
had experienced smallpox.

They had the scars,

or they had it as children.

But there was no immunity
in the new world.

There was no immunity
among kids.

There was no immunity
among adults.

And so,
when this new disease came,

everybody was vulnerable.

And so
it spread like wildfire.

Shatner:
Although the exact numbers
will never be known,

many experts estimate

that a staggering 95%
of the indigenous population

would eventually die
from smallpox.

But what's even more chilling

is the fact
that smallpox ran rampant

for thousands of years.

Gronvall:
I am astounded

by how far back smallpox goes.

For most
of human recorded history,

we believe it's the same strain

that was infecting
one person after another,

this human chain of infection.

The egyptian pharaoh ramses v
had scarring on his face

that's consistent with
smallpox.

Shatner:
It is estimated that smallpox
has killed

between 300 and 500
million people

in its more than
10,000-year existence.

Which begs the question:
How did we finally beat it?

Well, it just so happens
that the cure for smallpox

was discovered in a small
english village in the 1790s.

Gronvall:
In the late 1700s,
doctors were noticing

that milkmaids did not seem
to be affected by smallpox,

and their complexions remained
unscarred.

And people were starting
to make that connection

that there might be immunity
from catching

a different kind of pox virus,
cow pox.

So milkmaids were exposed
to the cow pox virus,

probably got infected,

and were then immune
to smallpox.

Edward jenner was
an english physician,

and decided to test
this observation,

and took a piece of an ulcer
from a cow

that was infected by cow pox,

and gave it to
an eight-year-old boy.

And then, a little bit later,

gave this little boy
a dose of smallpox.

Fortunately, the eight-year-old
boy did not develop smallpox

and was actually protected.

Because it wasn't, like,
a direct viral intake,

you would get, like, a slightly
lesser version of the disease.

But because you had been
exposed to it,

you would, of course,
then have immunity.

So it was probably
the first instance

of a crude version
of vaccination.

Shatner:
As it turns out, edward jenner's
revolutionary experiment

is remembered today
for its inspiration,

its sheer audacity

and because it provided
a new defense

against infectious disease,

which we now refer to as
"the vaccine."

the word "vaccine" comes from
the virus name "vaccinia,"

which was the virus that was
the cow pox-derived virus

that left people
immune to smallpox.

Vaccines prevent disease,

and some vaccines
can last for decades,

and some vaccines need to be
given every year.

For smallpox, people had to
get vaccinated every ten years.

Shatner:
Vaccines are humanity's
single greatest weapon

against plagues.

Rooted in science
and not superstition,

they provide a powerful way
to fight outbreaks.

Gronvall:
The last naturally occurring
case of smallpox

was identified in 1979,
and in 1980,

the world health organization
declared

that smallpox was eradicated.

So no longer spreading
from person to person.

Eradicating smallpox was the
biggest public health victory

in the history
of the human race.

Shatner:
The eradication of smallpox
is the most famous use

of a highly-effective vaccine,

but there are some diseases
that are harder to cure.

Michio kaku:
There are viruses

for which we have
no vaccines at all,

because they mutate too rapidly.

And so, because viruses mutate,

there's a certain limitation to
what you can do with vaccines.

Dasgupta: The minute
you get too confident,

and you think that
we defeated mother nature,

somehow, it always
finds a way to come back.

Shatner:
Vaccines are one of mankind's

greatest scientific triumphs.

But not all medical recoveries

can be easily
explained by science.

Sometimes, the body's reaction

to an infection is so bizarre
and so inexplicable

that it can only be
described as...

Miraculous.

Shatner:
July 4, 1863.

Gettysburg, pennsylvania.

On the morning after
the bloodiest battle

of the civil war,

thousands of dead
soldiers lay strewn

across the blood-soaked
farmland.

But while the brutality of the
civil war is well-documented,

approximately two-thirds
of the more

than 600,000 deaths in the war

weren't caused by injuries
sustained on the battlefield,

but rather... By disease.

Fisher:
The civil war represents

the last major conflict that,
um, that humans experienced

um, before the,
sort of, the inception

or the origins of germ theory.

You can imagine the conditions

that soldiers live in,
crowded together,

substandard sanitation.

In some cases,

open wounds that aren't
being treated correctly.

Wynn:
It's really gross.

Everything smells terrible.

Uh, these doctors aren't
washing their aprons.

They can't explain where they're
getting these diseases from,

how they may be spreading it.

Shatner:
As uncontrollable
infections ravaged

both union and
confederate encampments,

soldiers and their doctors
debated the cause

of their afflictions.

Many came to believe that
the air itself was poisoned.

Dasgupta:
When we talk about

some of the deadliest viruses
that we know,

some of them get transmitted by
respiratory droplets, the air.

When you cough, when you sneeze,
just by talking.

So maybe they weren't too off
by saying the air is bad.

Shatner:
In the mid-nineteenth century,

little was known
about disease control

or preventing
the spread of germs.

But as the scope
of the war widened

and the ferocity
of infectious outbreaks resulted

in even more
horrific causalities,

doctors were forced to expand
their knowledge of diseases

and how to contain them.

Wynn:
They realize that

maybe a barn isn't
the best place to be doing

amputations and open surgeries.

So, as the war goes on,

there's beginning
to be an understanding

of what medicine should be.

Things like triage,

things like an ambulance system,
hospitals--

these are all established
during the civil war

in the united states
for the first time.

Shatner:
In many ways, the civil war
marked the beginning

of medical science as we know it

and the end of mankind's

superstitious attitude
towards disease.

But there is one event
on the battlefield

that medical historians still
struggle to explain to this day,

because it simply
defies understanding.

April 7, 1862,
hardin county, tennessee.

Union and confederate forces
square off

in one of the bloodiest
confrontations

of the civil war--
the battle of shiloh.

After two days
of vicious fighting...

(yelling)

...More than 20,000 men
lie dead or dying.

Wynn:
So, ulysses s. Grant
is the commander

of the union army
at this battle.

He went out, and looked
over the battlefield,

and he could see that there were
so many soldiers who had been

wounded and killed that he could
have walked across one side

of the battlefield to the other

without ever
touching the ground,

walking from body
to body to body.

Shatner:
As night falls
over the battlefield,

many injured soldiers
lie helpless,

hoping to be rescued before
their wounds become infected.

What happens next is one
of the enduring mysteries

of the civil war.

Wynn:
Soldiers are out
between the lines,

wounded during the course
of the battle.

It's cold at night.
They're out there shivering.

And they happen to look down
at their shattered arm or leg,

and they notice this soft,
faint, bluish-greenish glow

seeming to come off
their wounds in the darkness.

There was a connection that was
being made amongst the soldiers

that those who experienced
this glowing wound effect

seemed to have better outcomes

when they went back to the
field hospital, and it seemed

as though their wounds may not
have been as infected.

Bidmead:
They termed
this bluish-green glow

angel's glow.
Why?

Because, to them,
it looked like a halo.

Mystical light surrounding them.

So, it was a way
of them thinking that god

or the angels were protecting
these particular soldiers.

Shatner:
Was the so-called angel's glow

a type of divine intervention

that somehow protected certain
soldiers from deadly infections?

Perhaps. But recently,
a new theory has surfaced--

one that suggests
this phenomenon

may have had a more
conventional explanation.

It wasn't until many years,
like 150 years later,

that a 17-year-old high
school student visited shiloh,

and he decided
for his science project

to research bacterium
that glows.

And they were able to find out
that there was a bacteria

that would emit some sort
of parasitic worm.

It would get into the veins,
and then it would glow.

Shatner:
Could the angel's glow

really have been a sign
of a type of bacteria,

rather than guardian angels?

And if so, could this bacteria
have actually been responsible

for saving the lives
of the wounded soldiers?

Presumably, what happened
with those soldiers

with the angel's glow

is that those bacteria were
actually infecting their wounds.

And because those bacteria
exude a lot of antibacterial

and antimicrobial compounds,
they actually reduce the level

of infection in the soldiers

that they, that they,
uh, colonized.

Shatner:
The bacteria theory

is the best scientific
explanation we have

for what caused
the angel's glow.

If this incredible theory
is true,

then it seems
that some forms of bacteria

can actually help us
in the fight against disease.

But the soldiers
whose lives were saved

at the battle of shiloh
believed that what healed them

could only have
been sent from heaven.

Wynn:
We can't know what
those soldiers experienced

out there on the battlefield
between the lines.

They're in the dark,
they're suffering from shock.

Who's to say that they didn't
experience that

or that they did
experience that?

Guardian angels,
reaching down to comfort

and even cure dying soldiers
during the american civil war?

To some it sounds
like pure fantasy.

But to others, especially those

who've had their own
close calls with death,

there's no doubt that such
a notion is entirely plausible.

Let's face it: When dealing
with deadly diseases,

it's hard to be certain
of pretty much anything.

Not only do we often
know very little

about how to cure an illness,

we know even less about
where an illness comes from.

For instance, what if I told you

that what we commonly refer to
as the spanish flu

didn't come from Spain at all,
but from a remote army base...

...In kansas?

Shatner:
At the height of world war I,

more than 50 years after the end
of the american civil war,

soldiers from more
than 30 nations are engaged

in trench warfare
all over europe...

...And a new, unexpected enemy
emerges...

-(coughing)
-...The spanish flu.

Wynn:
Europe is awash

in the influenza virus.

They had a massive outbreak
of influenza,

and these soldiers serving
at the front lines

are directly impacted
on both sides of the conflict.

-(coughing)
-the symptoms
were pretty horrific,

and so these soldiers
were not capable of performing

their duties, and many of them
actually die of the disease.

Gronvall: We're used to the flu,
but the 1918 flu

had more severe symptoms
and lingering effects.

When the flu
first started spreading,

their skin turned blue.

They just had no oxygen
in their blood.

It was not uncommon for people
to lose all their hair.

It was not uncommon to have
neurological side effects.

Wynn:
The 1918 influenza strain

caused an incredibly high fever,
it caused coughing.

In many cases, patients' lungs
would fill with fluid

as this virus
is taking over their body.

That would cause
an immune system overreaction

and they would
essentially drown.

Shatner:
Medics on the front lines,

prepared for the ravages
of war,

look on in horror
as young, healthy soldiers

begin to die within days,

or even hours of showing
symptoms.

The spanish flu was caused by,
um, an h1n1 influenza virus.

And the particular strain
of the h1n1 virus

was a little unusual
amongst influenza viruses

in that it was much more
contagious, it was much easier

to expel and spread
between people.

In 1918, we still really were

sort of incapable
of stopping its spread.

This was right at the end
of world war I,

and so soldiers were, of course,
kept in close quarters

and barracks together.

And then, also, people were
sort of moving around the world

more than they probably normally
would have been

sort of traveling.

Um, and so those were some
of the factors

that caused it to spread
really rapidly.

Shatner:
Since finding a cure
for a mysterious virus

in the midst of a world war
is a difficult,

if not impossible undertaking,

both the central powers
and the allied powers

decided the best course
of action

was to downplay the threat posed
by the disease.

In fact, the 1918 flu
is called the spanish flu

not because it came from Spain,
but because,

initially, Spain was
the only country willing

to acknowledge its existence.

Gronvall:
The reason we think of it
as the spanish flu

is because Spain had
a free press at that time,

and the rest of the world
did not.

Spain was not involved
in world war I,

and their king ended up getting
the 1918 flu.

So it was a matter
of national interest,

and most americans
learned of the flu

from the spanish papers.

Shatner:
The so-called spanish flu
is estimated to have infected

one third of the world's
population at the time,

roughly 500 million people.

But while the press created
a lasting nickname

for the 1918 flu,

some researchers have suggested
that it actually originated

in the heartland
of the united states.

March 4, 1918.

Fort riley, kansas.

Before the so-called spanish flu
outbreak was reported in europe,

a private at this remote army
base in the united states

starts to feel ill.

Wynn:
In March of 1918, an army
private named albert gitchell--

he's a cook with the army--

he reports symptoms,
so he goes to the hospital.

Uh, he's sick,
he's-he's not feeling well.

He's got a bit of a cough,
bit of a fever.

In the end, he ultimately
goes in to work,

feeding all of these soldiers
in this army camp.

In the weeks that follow,
the members of this camp

come down with a pretty nasty
flu strain.

And there are no other outbreaks
similar to this at this point,

which suggests that
this outbreak is starting

at that camp, and potentially
with that soldier.

Colby:
There were 1,127 cases
just at fort riley itself,

and 46 people died.

So all these soldiers
at fort riley are thinking

they just had a bad cold,
or maybe even a mild flu.

They were eventually
all put on trains,

which spread all over
the country

going to various ports.

And then they were all
shipped off to europe

to fight in the war.

Shatner:
Many scientist now believe that
army private albert gitchell

was the first man
to contract the 1918 flu.

Gitchell spread it
to his fellow servicemen

when he served them food.

And soldiers
then were sent overseas

to fight in the war,
and they unwittingly

spread the disease
around the globe.

But of course that explanation
is only a theory.

The situation
fits the epidemiology,

the number of people
who got sick afterwards.

But whether we will
ever know for sure

who patient zero was,

or whether it absolutely
came from kansas,

it's hard to be absolutely sure.

It's really hard to learn
where any virus starts,

where any pandemic starts,
because you're not recording

everywhere all the time,

and having the scientific tools
in place

to be able to detect it.

Wynn:
The great mystery
of any of these pandemics

or public health crises
is where did it start?

And, ultimately,
why did it start?

And what were the circumstances
that allowed that to happen?

It's the story of how
we interact with one another,

and how we spread diseases
amongst each other.

If you track that
and you find that out,

we could prevent it
happening again in the future.

Shatner:
The spanish flu outbreak
lasted for three long years

and killed an estimated
50 million people

before society finally developed
enough collective immunity

for the virus to die out.

History shows us that no matter
how lethal a disease may be,

humankind has always found
a way to endure it,

whether by employing
medical breakthroughs

or sheer patience.

But what kind of illnesses will
we have to face in the future?

Could they be different than

what we've experienced
in the past?

And might they come to our
planet from another world?

Shatner:
British astronomer
sir fred hoyle

publishes a book titled
astronomical origins of life:

Steps towards panspermia.

In it, hoyle investigates
the controversial theory

of panspermia,
which suggests that

life on earth
did not originate here

but rather in space,

and that asteroids
carried the microbial

building blocks of dna
to our planet.

Kaku:
You cannot dismiss
the possibility

that maybe life
came from outer space.

That we were seeded.
Seeded by asteroids or comets

that then put
their organic materials

onto the planet earth.

And so there's a new theory
in astronomy that says that

the solar system
is like a ping-pong game

with meteorites carrying
microbial lifeforms,

going back and forth
between venus, mars,

the earth and the moon.

This has given momentum
to the panspermia theory.

Shatner:
Some scientists have suggested
that if the theory

of panspermia is true,

then it's possible that
extraterrestrial viruses

could also travel here,
bringing with them diseases

that would be much different

from the ones
that exist on earth.

Michael dennin: When you
think about the core elements

of viral plagues-- those
are the four genetic codes,

dna or rna within
a protein shell--

that's something that's
easier to imagine being stable

deep inside an asteroid,
and safe.

And so any sort of virus
or plague,

you can imagine them
starting from

one of these asteroid events.

A space plague
is a leap into the unknown.

We have no way of knowing
what kinds of dna,

or maybe a modified dna version
exists in outer space.

We have never seen other kinds
of viruses from outer space

that can infect earthlings.

So right now we simply
don't know the answer.

Dennin:
I think if a plague
came from outer space,

just like the way some
of the plagues we know

jump from animals
to humans, suddenly,

any sudden change
in the viruses

or bacteria that are
attacking you as a human,

your immune system will not
have a defense to, most likely.

These dramatic events,
whether it's from space

or a sudden jumping
from animals to humans,

are the reason these plagues
can be so devastating.

Shatner:
A plague from outer space?

While that may seem
like a far-fetched notion,

it's a possibility that
science must be prepared for.

Wynn:
There are always
these viruses out there,

these things that
we can't explain.

It's important for us to
always be vigilant, to be aware

and to have our public
health authorities

always on the lookout.

So we can never
put our guard down.

Dennin:
Hopefully, the faster we are

and the better we are
at bioengineering,

the faster we can make vaccines
and countermeasures.

It's key to have them so that
we can make ways

to protect ourselves.

Preparing for any disease
is complex,

and it requires a lot of, um,
mobilization of government,

public health, and the science
to be able to figure out

what happened, and to prevent it
from happening again.

To be able to halt transmission
of this disease, whatever it is.

It becomes a detective story
as well.

You need to figure out
where it came from

and how to attribute
the disease.

It's a mystery that
our lives depend on,

and we need people
to be working on that

and thinking about that.

Perhaps what makes
deadly diseases so frightening

is that we never know when
they're going to strike next.

And that uncertainty
is also what forces us

to ask ourselves
are we really safe?

Well, the truth is that
only time will tell.

Which means that,
at least for now,

these questions
will remain unexplained.

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