Right. Saying plague = fascism makes fascism sound like "just one of those unlucky things" that sometimes happens and nobody is implicated in it. Which is crap.
I can sort of see the quarantined city = life in a totalitarian state, except that the quarantine was such a minor part of the novel, for me. Like, it was a psychological blow, for all the people who couldn't leave; but mostly it was just a thing that you do when you've got plague in your city, another detail to chafe at. People weren't restricted from going to churches -- there were standing room only crowds! -- and bootlegging and smooching and smuggling all continued as always.
And anyway, the point of the novel, for me, was that the plague would run its course, and some would die and some wouldn't, and all that could be done was pitch in an ease the suffering of the ill and the frightened. Dilletante Volunteer Boy's death isn't a tragedy or a wild statement against fascism or plague or anything -- it's just a death, and the virtuous as much as the shitty are cut down. And after all, the only thing the doctor could offer was comfort, in his doctoring people, and memory, in his recording what he witnessed.
Nunberg's article brought up a Camus quote (didn't say where it's from) to the effect that Robespierre-style "terror" was in love with the absolute, and thus akin to fascism, which I think is true, but I can't for the life of me relate that to The Plague.