The covered entity (CE), Cook County Health & Hospitals System (CCHHS), reported that its business associate (BA), Experian Health (Experian), discovered an error in the upgrade of two billing platforms which resulted in the delivery of protected health information (PHI) to the wrong recipients. The PHI involved included names, dates of birth, treatment information, and health insurance information. This breach affected 727 individuals. CCHHS notified HHS, affected individuals, the media, and provided substitute notice. To mitigate this issue, Experian reverted back to its older billing platform to rectify this issue.