Ethical Dilemma

You are a doctor, a pediatrician. You have a patient who is 16 and was born with HIV. He has no idea. His parents and you know, but they have decided to wait until he is older to tell him and because he is under 18 you have a verbal confidentiality agreement with the parents. This kid comes in alone without his parents for a check up. He tells you he wants to have sex with his girlfriend and they're thinking about it. You can't tell his parents because of the confidentiality agreement you have with him because he is your patient. What do you do? You can't say anything to either party that alludes to the danger or situation, but if you do nothing you risk a 16 year old girl getting HIV.