I know this. This week, I have become almost an expert on AIDS. When you get HIV, the virus incubates with almost no symptoms at all, just quietly, slowly eating away at your T-cells (your immune system). This occurs for about ten years, although it's different for everyone. When your T-cell count drops below 200, that's when the virus has technically become AIDS. Drugs like AZT only delay this moment. Once you have full-blown AIDS, it can take a year and a half for your body and mind to completely waste away. People get really sick really quickly.
Presumably, Roger contracted the virus relatively recently, since he found out he had it from April less than a year ago. He almost certainly hasn't had it long enough for him to be physically ill. We don't know about anyone else, but that explains him.
Another explanation is that HIV weakens your immune system. So it's very easy to get sick. People can die from pneumonia when they have AIDS. I'm guessing Mimi caught something or other while she was living in the park and her body wasn't able to fight it.
Just a theory.
Also, when Benny says, "You, me, Collins, and Maureen," he's responding to Roger saying, "Remember? You lived here." So I always assumed he was using the plural "you" and referring to both Mark and Roger.
Nothing matters but knowing nothing matters. ~ Wicked
Everything in life is only for now. ~ Avenue Q
There is no future, there is no past. I live this moment as my last. ~ Rent
"He's a tramp, but I love him."