THREAD: Photo of a smallpox patient, 1908. Smallpox is one of the deadliest & most contagious diseases known to mankind. The virus killed over half a billion people in the twentieth century alone—three times the number of deaths from all of the century’s wars combined. 
The human species is the only natural host of smallpox. No other organism can harbor the virus. Once inside the body, it begins replicating itself millions of times over. The incubation period is around ten days, during which time an infected person shows no signs of being ill.
Afterwards, the patient develops a high fever and aches, followed by a rash on the face, hands, and feet. Smallpox blisters are hard to the touch, and filled with a clear, faintly opalescent pus. Some cases develop into hemorrhagic smallpox, which causes the skin to slough off.
On May 8, 1980, the World Health Organization (WHO) announced the eradication of smallpox. This was an unprecedented event in history, signaling the first and only annihilation of a human disease. It has since been hailed the single greatest humanitarian achievement of all time.
The victory—which saved tens of millions of lives—was brought about through a campaign of rigorous vigilance and systematic vaccination, led by the American epidemiologist and “disease detective” Donald A. Henderson.
But the story of mankind’s struggle with smallpox is much older than most people realize, for the WHO’s announcement in 1980 fulfilled the lifelong dream of the English country doctor Edward Jenner, who first tested his vaccine on a human on May 14, 1796.
Jenner had noticed that dairymaids who contracted cowpox never developed smallpox. Working from this observation, he infected an eight-year-old boy named James Phipps with the cowpox virus by inserting infective matter into an incision he had made in the boy’s arm.
Phipps developed mild symptoms of the disease, which disappeared within days. Two months later, Jenner exposed the boy to pus from a fresh smallpox lesion. To his delight, the virus did not affect him. Phipps had developed immunity to smallpox.
The prominent Scottish physician Sir Walter Farquhar advised Jenner that if he kept the nature of the vaccine a secret, it could yield him a nest egg of as much as £100,000. But Jenner nurtured no such ambitions.
In 1798, he had a windowless hut built in the corner of his garden. Jenner christened it the “Temple of Vaccinia.” It not only became a beacon of hope for the poor who sought protection against smallpox, but it was also the site of the first public health service in Britain.
The concept of vaccination dates back much further than most people realize. You can visit @DrJennersHouse and the Temple of Vaccinia today. Follow them for more on Edward Jenner and the history of vaccines.
