Aztec doctor treating people with smallpox (1500s AD, Codex Mendoza)
Like many other diseases, including the current pandemic, smallpox probably got started in Central Asia. Around 150 AD (almost two thousand years ago), smallpox spread from Central Asia west to the Parthians and east to China. Not long after that, smallpox reached Europe and North Africa with returning Roman soldiers (and probably other travelers). About two to five out of every ten people who caught it died, which is more than ten times as many as corona kills (the corona kills one or two out of every hundred people). In China, the smallpox epidemic may have helped to collapse the Han Dynasty about 200 AD.
There was another big outbreak of smallpox in Constantinople a few centuries later in the 500s AD, where it weakened Justinian’s Roman Empire and helped to prevent him from reconquering the western Mediterranean. But because once you’ve had smallpox you generally can’t get it again, the disease tended to die out when it couldn’t find anyone new to infect in your city.
By about 900-1000 AD, Indian and Chinese doctors had figured out how to inoculate people against smallpox by giving them tiny doses of it. Inoculation wasn’t completely safe – some people got smallpox from it, and died – but it was safer than having smallpox. So many people chose to be inoculated.
Nobody in the Americas had had smallpox. So when Europeans came to the Americas, they brought it with them accidentally and gave it to the Native Americans they met. More than half of the Americans who got it died – smallpox (together with other European and African diseases like malaria, dysentery, cholera, typhus, and yellow fever) killed so many Native Americans that they were unable to stop Europeans from taking over their land.
Smallpox was still killing Europeans too. Louis XV of France died of it in 1774. But in the late 1700s and early 1800s, doctors slowly figured out how to vaccinate people without killing them, by making smaller doses of weaker versions of the virus. In the 1900s, there was a worldwide campaign to get rid of smallpox entirely, and it worked. The last case of smallpox in the world was in 1977 – nobody has had smallpox since then.
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