While living on the streets, why is Alice sick?

Alice is sick because of the elements (she has a cold and a fever), because she is frightened and lonely, and most of all.... she is sick because she is going through withdrawal.

The goddamned rain is even worse than yesterday. It's like the whole sky is pissing on us. I tried to go out once, but my cold is so bad I was chilled to my ass before I'd even gotten to the goddamned corner, so I came back and went to bed with my clothes on, trying to curl up enough so my body heat would at least keep me from dying. I guess I've got a high fever, because I keep drifting off—that's the only bejesus thing that keeps me from croaking. Oh, I need a fix so bad! I want to scream and pound my head against the wall and climb the damned dusty, faded stringy curtains. I've got to get out of here. I've got to get the hell out of here before I really blow my cool all the way. I'm scared and lonely and I'm sick. I'm as sick as I've ever been in my life.