Plague - The Destroyer of Empires

[Nathan Ross]

Regarding mortality numbers... I'm inclined to believe mortality higher than 50%, perhaps much higher. 

As I mentioned above, it's hard to assess these things, but those who've studied the Antonine Plague have come up with mortality figures ranging from 1-2% to about 15%. Certainly nothing like 50%!

These studies use epigraphy, literary accounts, papyrus evidence of tax payments, coin issues, evidence from later legislation and possible mass burials - they are not guesswork.

One interesting recent study might be this one: Modeling the Antonine Plague. But sadly only the introduction is available in English...

If it's 50% or higher, then that's enough to cripple the state.  If it was 10-15%, perhaps not so much. 

The Roman state was not crippled during this period, so we have our answer to that one!

centralized civilization in central Europe did not exist prior to the Black Death. 

I'm pretty sure it did! Medieval history is not my thing, but large stable monarchies had existed all over Europe for many centuries before the Black Death, while the Italian states had a republican system in place throughout the middle ages. 'Feudalism' was a social system, not a form of government.

Find one example where a plague has hit a civilization and that civilization remained intact without changing it's form of government. 

The Black Death did not cause the collapse of monarchy (or even of individual nation states) in Europe. The Great Plague of 1665 caused no political change in England.

Why do you assume that the Antonine Plague wasn't absolutely devastating?  Because it wasn't recorded in literature like other epidemics?... That could in fact be evidence that it was even more virulent and deadly than other epidemics, because the death toll was so high that it prevented historians from recording that period of history.

In fact, almost nothing is known from 160-200 AD.  It's shrouded in darkness.

On the contrary, we have surviving works by quite a few contemporary writers of the period: Marcus Aurelius himself, the historians Herodian and Cassius Dio, and the medical writer Galen, amongst others. Later historians fill in further details. It's the later period of the 'third century crisis' that's comparatively dark.

Oddly enough, those writers alive at the time make only occasional references to the plague. Marcus Aurelius mentions it three times in his Meditations, while Galen (who was in Aquileia during the outbreak there) says that the troops suffered greatly, but does not imply there was anything unusual about that.

Cassius Dio describes the later outbreak in Rome under Commodus as the worst ever - that's where his figure of 2000 deaths a day comes from, which isn't too huge in a city of c.1 million, and is comparable to previous reported outbreaks under Nero and Titus. Christian writers of the third century refer only to periodic outbreaks of plague, but do not suggest any major lasting depopulation.

It's only later writers - 4th and 5th century - who describe the Antonine Plague as a major catastrophe. It could be that, with the benefit of hindsight, they were able to see a pattern in what had appeared at the time as scattered individual events. But it could be that these later writers had exaggerated a series of relatively minor outbreaks into a major global epidemic. We can't tell either way.