The Plague question

Totalitarianism

The commonality we share as humans and how we can work together and help each other while knowing the fate we all share

The plague is any kind of issue challenging greatly the current, persevering attitude of the majority of people, something that challenges their idleness. Camus calls these "humanists" in the very beginning of the novel and says that they "forgot to be modest"

The Plague, and the novel itself, are a test in patience.

I am with Ian here. I think it is absolutely totalitarianism Camus has in mind. His own experience, and his famous ending with plague hiding among common items, reinforces this, IMO.