The Antonine Plague
A devastating pandemic — likely smallpox — swept through the Roman Empire, killing an estimated 5 million people and weakening Rome's military and economic foundations.
In 165 CE, Roman soldiers returning from campaigns in Mesopotamia carried a deadly disease back to the heart of the empire. The Antonine Plague, named after the ruling Antonine dynasty, spread across the Roman Empire over 15 years, killing an estimated 5 million people — roughly 10% of the population and up to a third of the army in some regions. The physician Galen documented symptoms consistent with smallpox: fever, diarrhea, and skin eruptions. Among its victims was co-emperor Lucius Verus in 169 CE; Marcus Aurelius himself may have succumbed to a recurrence in 180 CE. The plague weakened Rome's military capacity, disrupted trade routes, and accelerated the social and economic pressures that would eventually contribute to the empire's decline.
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