The individual's right to privacy and your duty to maintain confidentiality are of prime importance and everything possible must be done to preserve them. There are situations, though, where other rules apply. For example, the Ontario Health Protection and Promotion Act provides that where a patient has or may have a reportable disease, the physician shall report it to the medical officer of health. Reportable diseases are listed in the regulations and include AIDS/HIV, gonorrhea, syphilis and herpes. The Ontario Personal Health Information Protection Act, the Policy Statement of the College of Physicians and Surgeons of Ontario, and the CMA Code of Ethics permit disclosure of personal heath information about an individual if the custodian of such information believes, on reasonable grounds, that it's necessary for the purpose of eliminating or reducing a significant risk of serious bodily harm to a person or group. In such cases, every reasonable effort should be made to obtain the patient's consent. It's further suggested that the physician document all details of the situation and that the patient be advised of the decision to disclose.

As a doctor, you must act in accordance with the law, and you must also use your best judgement. Given the importance of the confidentiality issue and the emphasis placed on physician-patient privilege, it might be advisable to consult with your college or the Canadian Medical Protective Association before making a final decision. This would help protect you should the patient ever lay a complaint of malpractice for disclosing information, or should the third party ever claim damages for failing to disclose and protect. This would be especially relevant in your case as the third party is also your patient and you have an obligation to consider his or her well-being and provide appropriate care.