Nicole Pasulka provides a primer on HIV transmission laws:
According to the Center for HIV Law and Policy, 32 states and two US territories have some sort of HIV-specific criminal transmission statute. 45 states have laws against HIV-positive people not disclosing their status during sex, acts of prostitution, needle exchanges, or when making organ, blood or semen donations or have prosecuted people for these behaviors under general felony laws. In 13 of those states, there are laws against HIV-positive people spitting on or biting someone, neither of which has ever been proven to transmit HIV.
One issue here is whether other comparably transmissable diseases – like Hepatitis C for example – are treated the same way. I suspect not, but I don't know the answer.
The Dish 