10,000 years ago,

a deadly virus arose in northeastern Africa.

The virus spread through the air,

attacking the skin cells,

bone marrow,

spleen,

and lymph nodes of its victims.

The unlucky infected developed fevers,

vomiting,

and rashes.

30% of infected people died

during the second week of infection.

Survivors bore scars and scabs

for the rest of their lives.

Smallpox had arrived.

In 1350 B.C., the first smallpox epidemics

hit during the Egypt-Hittite war.

Egyptian prisoners spread smallpox

to the Hittites,

which killed their king

and devastated his civilization.

Insidiously, smallpox made its way around the world

via Egyptian merchants,

then through the Arab world with the Crusades,

and all the way to the Americas

with the Spanish and Portuguese conquests.

Since then, it has killed billions of people

with an estimated 300 to 500 million people

killed in the 20th century alone.

But smallpox is not unbeatable.

In fact, the fall of smallpox started

long before modern medicine.

It began all the way back in 1022 A.D.

According to a small book, called

"The Correct Treatment of Small Pox,"

a Buddhist nun living in a famous mountain

named O Mei Shan

in the southern providence of Sichuan

would grind up smallpox scabs

and blow the powder into nostrils of healthy people.

She did this after noticing

that those who managed to survive smallpox

never got it again,

and her odd treatment worked.

The procedure, called variolation,

slowly evolved

and by the 1700's,

doctors were taking material from sores

and putting them into healthy people

through four or five scratches on the arm.

This worked pretty well

as inoculated people would not get reinfected,

but it wasn't foolproof.

Up to three percent of people

would still die after being exposed to the puss.

It wasn't until English physician Edward Jenner

noticed something interesting about dairy maids

that we got our modern solution.

At age 13, while Jenner was apprentice

to a country surgeon and apothecary

in Sodbury, near Bristol,

he heard a dairy maid say,

"I shall never have smallpox, for I have had cowpox.

I shall never have an ugly, pockmarked face."

Cowpox is a skin disease

that resembles smallpox and infects cows.

Later on, as a physician,

he realized that she was right,

women who got cowpox didn't develop

the deadly smallpox.

Smallpox and cowpox viruses are from the same family.

But when a virus infects an unfamiliar host,

in this case cowpox infecting a human,

it is less virulent,

so Jenner decided to test

whether the cowpox virus could be used

to protect against smallpox.

In May 1796, Jenner found a young dairy maid,

Sarah Nelmes,

who had fresh cowpox lesions on her hand and arm

caught from the utters of a cow named Blossom.

Using matter from her pustules,

he inoculated James Phipps,

the eight-year-old son of his gardener.

After a few days of fever and discomfort,

the boy seemed to recover.

Two months later, Jenner inoculated the boy again,

this time with matter from a fresh smallpox lesion.

No disease developed,

and Jenner concluded that protection was complete.

His plan had worked.

Jenner later used the cowpox virus

in several other people

and challenged them repeatedly with smallpox,

proving that they were immune to the disease.

With this procedure,

Jenner invented the smallpox vaccination.

Unlike variolation, which used actual smallpox virus

to try to protect people,

vaccination used the far less dangerous cowpox virus.

The medical establishment,

cautious then as now,

deliberated at length over his findings

before accepting them.

But eventually vaccination was gradually accepted

and variolation became prohibited

in England in 1840.

After large vaccination campaigns

throughout the 19th and 20th centuries,

the World Health Organization certified

smallpox's eradication in 1979.

Jenner is forever remembered

as the father of immunology,

but let's not forget the dairy maid Sarah Nelmes,

Blossom the cow,

and James Phipps,

all heroes in this great adventure of vaccination

who helped eradicate smallpox.