Thursday, January 06, 2022

Plagues and Pandemics (3) Bubonic Plague in Rome

By the fifth century, the Roman Empire was under serious pressure with large hostile population groups were invading from the East. The Black Death first appeared in Egypt in AD 541 and from there it quickly diffused throughout the Empire. It persisted for two centuries. The last recorded cases were in AD 749.

The Black Rat that carried the plague-bearing, oriental rat fleas were prolific breeders. They were crafty climbers and willing travellers on ships and waggons. The Rome Empire had hundreds of granaries storing grain to feed soldiers, so it was an ideal home for rats. The plague spread swiftly by sea and slowly by land to every part of the empire.

The agent that causes bubonic plague is a bacterium called Yersinia pestis. It lives and travels on rats. When the rat’s immune system fought back against it, the bacterium concentrated in the blood of the dying rat. When the rat population died, the desperate fleas would jump onto humans looking for more blood to feed on.

The injected bacterium multiplies and blackens the tissue under the skin. The lymphatic system drains the bacteria into the nearest lymph node, where they multiply explosively, causing the node to swell, forming buboes, often in the groin or under the arms. A secondary infection in the blood would cause haemorrhages that appeared as small black spots. Blood vomiting and diarrhoea would follow.

Victims first suffered pain, fever and boils, then swollen lymph nodes and blotches on the skin. After that, they vomited blood and died within a few days. Case fatality was often as high as 80 percent. The bacterium can also be spread by aerosol droplets causing pneumonic plague. This caused fever chest pain and a bloody cough. Case fatality was often 100 percent.

The ultimate death toll is hard to estimate, but the best estimates are that half the population of the empire were carried off by the plague. The population of the city of Rome dropped from over a million to as few as 20,000.

The economic and military consequences were serious. Harvests rotted in the fields, so food was scarce. Taxation was impossible to collect, so the State struggled.

The Roman army fielded half a million men who were supported by an extensive logistical system. With dwindling taxation, the army could not be paid, so the defence of the empire collapsed. The plague decimated the Roman soldiers so people from the periphery of the empire had to be recruited to take their place, but they were not as loyal to Rome.

The plague destroyed the trade that had sustained the wealth of the empire. Towns shrunk in size and many villages and manor farms disappeared. Many people went back to subsistence farming as the collapse of markets reduced their ability to trade. Building stopped, so demand for labour collapsed.

The persistence of the plague strangled hopes of a recovery. Environmental change made the situation worse. In AD 536, a year without sun, possibly caused by a serious volcanic eruption somewhere in the northern hemisphere, ushered in a season of bad weather and poor crops. This colder period lasted for a century and a half.

War, plague and climate change reversed a millennium of material advance and contributed to the collapse of the Roman empire.

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