The patients right to privacy and confidentiality are valid ethical laws, although so is being honest, and not giving false information.
In any case that you feel, or the patient tells you that the parents may have been infected with AIDS on their stay, that is a different issue. "Good practice will incorporate protecting confidentiality when protecting that confidence does not harm others"(Hall 356). "The nurse cannot ethically (nor legally) keep confidences if that causes harm to the patient, or to other people"(Hall 356).
To the best of my knowledge the parents have not yet become infected, it is hospital standard to wear gloves and provide clean and sterile techniques; there may even be an isolation precaution up, to prevent the spread or contamination to others. Everything in my power would be done to prevent any family members or others from getting infected with the AIDS virus on their stay. .
The reason I choose not to tell the parents is to prevent all of the negative outcomes that may possibly happen as a cause of my telling. One for example is that the family may disapprove, he will then have a bad reputations that may spread to the rest of his family and friends, as well as the fact that his parents and family may decide not to stay at this point in his life where he is dying, and have no support. The patient is already facing death, but he may become depressed for these other reasons as well. On the other hand, another possible outcome may be that the information about his disease was revealed and the parents support their son's decision, and remain with him until he passes away. Giving him a more pleasant and supported and of life. There are other possible outcomes, but theses seem to be the prevailing reactions given by parents, to support or in a sense disown their son.
On the other hand it is also ethically just, to talk to the patient about informing any partners he may have had in the past.