Mannahnin
Scion of Murgen (He/Him)
If it's any consolation, JMal didn't use that word in the first article of his I found on the topic. I don't know if he used it elsewhere.It could equally be that they didn't think real-world infectious diseases had enough (or the right) resonance for many western audiences in the early 00s. Or the simple 'D&D isn't set in the real world' mindset that made them remove Lucerne hammers and include double-bladed swords, etc.
Regardless, while I'm dubious of any grand meaning to the disease charts (any more than whether ST:ToS has Spock suffering from space-measles instead of leukemia or diphtheria), I think it is a reasonable premise -- and significantly more persuasive than a notion that everyone has to read a specific select list of supporting fiction or some other claim. That said, if Maliszewski actually used the term "decadent," I'm going to roll my eyes a little, because, good lord, can't we just say we prefer X over Y without having to imply that Y is somehow indulgent, inferior, condescending, worthy of condescension, or reflecting a state of moral or cultural decline?
I could imagine him using it, though I imagine it'd be at least a bit ironic. He has tended to take a very nostalgic, and sometimes elegiac, tone.