That's a great post, but I think it's going too far to say that the Romans understood disease.
Sure, I agree that I oversold it, and should have worded it more carefully. But, I'll point out that "understand disease" is not a single threshold. One could contest the claim that we understand disease. The following claims seem to be individually more likely than not: some educated Romans knew that sanitation and disease were linked, designed sanitation around their knowledge of disease, and that epidemic diseases were caused by invisible agents that were physically transmitted. It seems much more likely than not that Roman knowledge of disease- both theoretical and practical- surpassed medieval knowledge of disease for the majority of the medieval period.
I think it's worth pointing out that early moderns didn't seem to notice that disease in army camps was a big deal.
Really? I get the impression that they knew disease inside a city could end the siege in the attacker's favor, and disease outside a city could end the siege in the defender's favor. I think they thought it was an unavoidable fact of life, though, which might cash out as 'not a big deal.' (For example, I get the impression that the British Navy lost a ton of men to scurvy, but didn't embark on many explicit attempts to figure out and prevent scurvy because it wasn't obvious to them that such a thing was possible / they didn't know where to start.)
Sorry I wasn't clear, as you can tell from the other thread with Lumifer, but I really do mean to object to the claim that Roman knowledge contributed to the design of the camps.
Yes, early moderns did notice that epidemics were important in sieges, but they didn't seem to notice that disease mattered at other times.
Related: Son of Low Hanging Fruit, Low Hanging Poop
A post by Gregory Cochran's and Henry Harpending's blog West Hunter.