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Ten thousand years ago,

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a deadly virus arose in northeastern Africa.

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The virus spread through the air,

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attacking the skin cells,

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bone marrow,

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spleen,

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and lymph nodes of its victims.

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The unlucky infected developed fevers,

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vomiting,

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and rashes.

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Thirty percent of infected people died

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during the second week of infection.

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Survivors bore scars and scabs

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for the rest of their lives.

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Smallpox had arrived.

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In 1350 B.C., the first smallpox epidemics

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hit during the Egypt-Hittite war.

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Egyptian prisoners spread smallpox

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to the Hittites,

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which killed their king

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and devastated his civilization.

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Insidiously, smallpox made its way around the world

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via Egyptian merchants,

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then through the Arab world with the Crusades,

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and all the way to the Americas

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with the Spanish and Portuguese conquests.

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Since then, it has killed billions of people

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with an estimated 300 to 500 million people

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killed in the 20th century alone.

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But smallpox is not unbeatable.

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In fact, the fall of smallpox started

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long before modern medicine.

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

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According to a small book, called

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"The Correct Treatment of Small Pox",

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a Buddhist nun living in a famous mountain

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named O Mei Shan

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in the southern providence of Sichuan

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would grind up small pox scabs

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and blow the powder into nostrils of healthy people.

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She did this after noticing

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that those who managed to survive smallpox

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never got it again,

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and her odd treatment worked.

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The procedure, called variolation,

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slowly evolved

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and by the 1700's,

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doctors were taking material from sores

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and putting them into healthy people

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through four or five scratches on the arm.

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This worked pretty well

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as inoculated people would not get reinfected,

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but it wasn't foolproof.

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Up to three percent of people

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would still die after being exposed to the puss.

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It wasn't until English physician Edward Jenner

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noticed something interesting about dairy maids

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that we got our modern solution.

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At age 13, while Jenner was apprentice

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to a country surgeon and apothecary

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in Sodbury, near Bristol,

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he heard a dairy maid say,

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

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I shall never have an ugly, pockmarked face."

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Cowpox is a skin disease

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that resembles smallpox and infects cows.

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Later on, as a physician,

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he realized she was right,

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women who got cowpox didn't develop

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the deadly smallpox.

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Smallpox and cowpox viruses are from the same family.

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But when a virus infects an unfamiliar host,

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in this case cowpox infecting a human,

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it is less virulent,

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so Jenner decided to test

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whether the cowpox virus could be used

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to protect against smallpox.

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In May 1796, Jenner found a young dairy maid,

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Sarah Nelmes,

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who had fresh cowpox lesions on her hand and arm

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caught from the utters of a cow named Blossom.

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Using matter from her pustules,

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he inoculated James Phipps,

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the eight-year-old son of his gardener.

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After a few days of fever and discomfort,

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the boy seemed to recover.

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Two months later, Jenner inoculated the boy again,

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this time with matter from a fresh smallpox lesion.

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No disease developed,

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and Jenner concluded that protection was complete.

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His plan had worked.

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Jenner later used the cowpox virus

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in several other people

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and challenge them repeatedly with smallpox,

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proving that they were immune to the disease.

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With this procedure,

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Jenner invented the smallpox vaccination.

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Unlike variolation, which used actual smallpox virus

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to try to protect people,

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vaccination used the far-less dangerous cowpox virus.

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The medical establishment,

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cautious then as now,

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deliberated at length over his findings

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before accepting them.

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But eventually vaccination was gradually accepted

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and variolation became prohibited in England in 1840.

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After large vaccination campaigns

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throughout the 19th and 20th centuries,

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the World Health Organization certified

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smallpox's eradication in 1979.

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Jenner is forever remembered

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as the father of immunology,

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

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Blossom the cow,

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and James Phipps,

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all heroes in this great adventure of vaccination

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who helped eradicate smallpox.