Original subtitles

how smallpox kills

variola is highly infectious

and catches a ride in small droplets you breathe in

immediately

it begins to infect the cells that line your throat

and starts killing them to cause chaos

why

to trick your body into giving it a lift

whenever cells in your body die of violent death

your immune cells

immediately stream to the site of infection

to help out in this case

that back fires horribly

as immune cells begin cleaning up dead cells

eating viruses and killing infected cells

variola infects a crucial cell of your immune system

your dendritic cells

intelligent cells that gather information

and leave the battlefield

to get help they enter your lymphatic system

a highway network that spans your entire body

and connects hundreds of immune bases

in these bases your heavy defenses are activated

and should be the last place

an enemy would want to invade

but Variolo wants to get here

for about 12 days

the virus quietly infects civilian and immune cells

jumping from cell to cell

infecting more and more of them

at some point a critical threshold is reached

and variola starts its attack for real

millions of viruses use the lymphatic highway

to spill into your blood and organs

infecting your whole body

suddenly variola is everywhere

but despite this global attack

your adaptive immune system is struggling to wake up

your immune cells look for

and use critical transmitters

called interference

to mobilize the body against viruses

interference as the name suggests interfere

significantly slowing down virus infections

but also

quickly activating millions of anti virus weapons

but variola is able to deactivate interference

which stuns the anti virus side of your defense system

other systems would usually help

like the complement system

a sort of mobile minefield that can destroy viruses

but variola manages to shut this down too

and so with little resistance

variola spreads everywhere

and infects billions of your cells all over your body

among the infected are your capillaries

the smallest blood vessels in your body

which die in great numbers

all this death activates an immune cell

that you really don't need right now

but that's attracted by death

the neutrophil normally an efficient killer of invaders

great and small

it's not very effective against smallpox

and even worse

neutrophils fight by vomiting deadly chemicals

which kills even more of yourselves

on top of that they order inflammation

fluids streaming from your blood vessels

into your tissue all over your body

as first millions then billions of yourselves die

you get a rash that only gets worse and worse

puss and a cellular junk fills it up

as your body swells up with hundreds of lesions

all over your skin and inside

even on your organs

all filled with billions of variola viruses

now the critical phase begins as you fight for survival

you burn up in a high fever

thousands of battlegrounds drain your blood of fluid

that streams into your tissue

and organs blood clotting appears all over your body

while floods of toxins from dead cells build up

and can cause organs to fail

your lungs fill up with fluid

making it harder and harder to breathe

one of two things happens now

either your immune system wrestles back control

heavy weapons have been dispatched

killing infected cells

cleaning up the thousands of infections one by one

killing variolo wherever it can be found

so you can slowly begin to recover

the immune system will forever remember variola

making you immune forever

or you die overwhelmed by the infection

and your immune system's panic

reaction to the body wide infection

about a third of people who can track smallpox

don't survive and if you survive

you're very likely branded by scars

and may even lose your eyesight or hearing