There are no effective privacy protections for information provided to an employer. Employers have a general duty to maintain employee confidentiality. In practice, though, if your employer breaches the duty there may be no way to get a satisfactory remedy. Consider very carefully before disclosing your HIV status, because once you have disclosed, you cannot take the information back. While your current boss or supervisor may be understanding, if your HIV positive status is on file then your next boss will also have access to this information and he or she may have a very different attitude.
Source: HIV/AIDS Legal Centre, Sydney http://halc.org.au/publications/guides-to-hiv-and-the-law/