As I follow the Charlie Sheen issue I have to wonder Where does his right to privacy end and the other person's right to know start? Considering he using Condoms and Precautions - Has a reasonable expectation that he will not infect any one - Does he have an obligation [legal or otherwise] to inform them of his status? This issue extends beyond that particular situation I wonder the same thing with the Transgender community. Where does their obligation to divulge their former gender come into play? Or Does it ever? Once they are 'reassigned' is their a legal obligation to inform their future lovers/spouse? I feel there are moral obligations but I think the legal obligations on informing people of various 'issues'/'situations' is very foggy. Rocket River
Not a lawyer but it seems the answer to every one of your scenarios is easily no, no obligation to disclose.
HIV, yes you should tell someone legally and morally. Transgender, no ones business unless in a relationship. Then I think there's a moral obligation.