Personal details of 1.2 million patients within the Cook County Health and Hospital System were exposed in a data breach earlier this year, the health agency said on Friday.

Perry Johnson and Associates Inc., a third party provider of medical transcription services, informed Cook County Health in July that it had experienced a “data security incident,” and an investigation was underway, according to the agency.

The investigation revealed that an unauthorized individual accessed the company’s systems where patient data was stored in April 2023. After learning patients’ information had been compromised, Cook County Health said it stopped sharing data with the company and terminated its relationship.

PJ&A acknowledged the following records of 1.2 million patients were among those affected: dates of birth, addresses, medical record numbers, encounter numbers, medical information, and dates/times of service.

Of the compromised records, approximately 2,600 may have included Social Security numbers, the health agency said.

Impacted patients are expected to be notified by mail starting next week, with a letter explaining more information about the incident and what steps they can take to protect their data. Those affected will also receive information on how to monitor their credit reports and place freezes on the reports if needed, according to Cook County Health.

Those whose Social Security numbers may have been accessed will be able to enroll in credit monitoring and identity protection services at no cost. Cook County Health said while it has no evidence that any personal information has been misused, it urges patients to monitor medical bills for any suspicious activity.