Which characteristic applies to breach notification?

The correct choice indicates that breach notification applies when one person's Protected Health Information (PHI) is breached. This is significant because the Health Insurance Portability and Accountability Act (HIPAA) requires covered entities to notify affected individuals when their PHI has been compromised. This requirement is foundational in safeguarding patients' rights and ensuring they are informed about breaches that could affect their personal information.

Even a single instance of breach can have serious implications for an individual's privacy and security, therefore the requirement to notify individuals reflects the importance of addressing even minor breaches swiftly. This characteristic emphasizes the need for entities to have robust data protection and notification protocols in place, regardless of the scale of the breach.

On the opposite side, notifications for breaches involving larger groups or specific thresholds, like those mentioned in the other choices, are generally provisions for aggregating notifications or additional reporting requirements but do not override the necessity to notify affected individuals in cases of any breach, no matter how small.