Final answer:
The most appropriate time to disclose the incident to the affected patients is when it is mandated by legal and regulatory requirements.
Step-by-step explanation:
The MOST appropriate response for the Chief Information Security Officer (CISO) of the hospital regarding when to disclose the incident to the affected patients is when it is mandated by their legal and regulatory requirements. In the case of a data breach, there are often laws and regulations in place that dictate when and how affected individuals should be notified. These requirements vary depending on the jurisdiction and the nature of the breach. By following legal and regulatory requirements, the hospital can demonstrate transparency and accountability to the affected patients.
Failure to comply with the legal requirements can lead to severe penalties, loss of patient trust, and damage to the hospital's reputation. Moreover, timely and mandated disclosure can also be seen as an ethical responsibility towards the patients, where their right to know and for privacy should be balanced against the hospital's operational procedures and reputational concerns.