The origins of smallpox
Not much is known about the origins of smallpox. Most likely it evolved from a virus affecting animals, such as cowpox, horsepox, or camelpox.
(Right) Carving from the ancient Mesopotamian city of Nineveh, approx 1400BC © unknownScientists believe the virus made the leap from animals to humans in about 10,000BC, when the first farmers made settlements in the river valleys of Egypt, the Middle East, India and China.
Smallpox in ancient history
Classical writers describe epidemics of a sometimes-fatal disease that caused a rash across the body. This was probably smallpox, although it’s hard to be sure because ancient authors didn’t distinguish between similar diseases like smallpox and measles.
(Right) Alexander the Great, whose troops were ravaged by smallpox during his march on India. (Mosaic found in the house of the faun, Pompeii) © unknwon Smallpox changed the fortunes of ancient civilizations. In 1350BC, Hittite armies were ravaged by smallpox caught from infected Egyptian prisoners of war. A thousand years later, the Carthaginian and Athenian empires suffered in their turn, and when Alexander the Great attempted to invade India in 327BC, his foot soldiers were struck down by a virulent and often fatal rash – almost certainly smallpox.
The disease entered China in about 250BC. The Chinese had built a wall to keep out the Huns, but it failed to keep out the virus they carried, and an “epidemic throughout the empire” followed.
Smallpox arrives in Europe
We don’t know exactly when smallpox reached Europe – but we know that ‘pox houses’ were built in the era of the Crusades, along the routes from Europe to the Holy Land. It’s likely that the movement of armies across Europe in these years hastened the spread of the disease.
(Right) Constantine the African inspects samples of urine. Public domain Some historians believe smallpox in the medieval period was just a minor variant of the disease – a childhood illness like measles, but less severe. It certainly wasn’t feared like bubonic plague was feared. But in the two hundred years that followed the Black Death, smallpox grew more and more deadly. By the 16th century it was a major killer.Smallpox was ‘endemic’ throughout Europe – meaning it was a constant presence. When the virus reached a dense population with low immunity, it became ‘epidemic’, and a major outbreak occurred. Epidemics were cyclical; with each passing generation, as immunity levels dropped, epidemics recurred.
Smallpox crosses the Atlantic
From the late 15th century onwards, adventurers sailed to the Americas in search of fish, fur and gold, and they founded colonies in the New World. They brought to the Americas many species previously unknown there, including horses, cows, wheat, honeybees and earthworms, transforming the ecology of the New World in the process. But without realizing it, they also brought something more deadly: the smallpox virus.
The native populations of the Americas had never experienced smallpox before. None were immune; they were a ‘virgin population’. So the disease spread with devastating effect. From the moment the first Europeans arrived in the Caribbean, whole tribes were wiped out. Half the native population of Puerto Rico died of smallpox within a few months in 1519.
Smallpox devastates the Nahuatl Natives. An illustrated panel from the Florentine Codex, c.1585. Public domain Later that year, when Spanish explorers encountered the Aztec civilization of Mexico, they carried the virus with them, and the natives “died in heaps, like bedbugs”. Within a few months half the Aztec population of thirty million people had died, and a few hundred Spanish conquistadors were able to conquer an ancient civilization.
Smallpox in North America
In North America, too, European viruses wiped out Native tribes. In the three years before the Mayflower landed on the coast of New England, ninety percent of the Massachusetts Natives died of disease.
An image of the "Great Dying," the cataclysmic scourge brought upon the native American population by epidemics in the early 17th century. © unknown Enormous epidemics soon swept westwards, inflicting terror and mass death among tribes along the Great Lakes: the Hurons and the Iroquois were especially hard hit. The tragedy continued well into the 19th century, as white America expanded westwards across the face of the continent.
White America suffered too. The city of Boston experienced eight epidemics in the 18th century, and in some of these epidemics more than half of the population were infected. During the Revolutionary Wars between the British and American colonists, smallpox altered military strategy and shifted the course of battles.