Do you inform?

Your best friend has a new partner who you don't like at all because you don't trust him. Every time you try explain this to your friend she just seems to ignore you and tells you how amazing he is.

One day you are carrying out HIV/AIDS testing on samples (you are a medical laboratory scienctist) and discover that her new partner is positive for HIV. You know to respect patient confidentiality you are not to tell anyone else, but you also know he is highly unlikely to inform her himself. You need to decide whether you should inform your best friend as it is highlyy unlikely he will do it himself or do you respect patient confidentiality and leave it up to him to inform anyone he wants to.