Elsie
Shopaholic
I suppose he could get hit by a car or something, but with a case that involves a deadly substance like thallium, I'd be willing to bet a few bucks that Sid fighting for his life involves that. (As I said before, that's my interpretation of limited information.)
That would seem to be a likely scenario, based on the limited information. I don't know anything about thallium (or if a situation like this would happen in reality), but if others have died, presumably from something to do with touching/handling the book or whatever, then Sid, by processing the body, would presumably get sick too (a bit like the itching powder in Child's Play is how I'm imagining it, he gets up close and personal with the body so is much more likely to come into contact with a dangerous substance on it).
Poor Sid, I do hope he's OK. As for seeing his family? That would be really great, but I'm not getting my hopes up that it will happen.