There's some confusion as to who is the real 'Patient Zero' is (if such a thing can ever really be truly established).
I believe Darren James worked with Bianca Biaggi on that ill-fated trip to Brazil (I think the scene is in "Split That Booty 2"), but some people, like Gene Ross, have put forward the theory that perhaps Lara Roxx herself was patient zero in this outbreak.
I'm sure Bianca also turned up HIV+, and that she got it from working with a tranny. I'm pretty sure the time frames match up, so it's very possible she gave it to Darren James.
As to what happened to Bianca after that, no idea...maybe smartt could tell us?