According to a recent survey,

respondents had the following privacy concerns regarding their health records:

• 16% were concerned with health records held by their health insurer
• 14% were concerned with records held by their hospital
• 11% were concerned with records held by their physician
• 10% were concerned with records held by their employer
• 5% said they have been notified that their medical records were compromised or accessed without their permission

Source: "Health Poll, Data Privacy," Truven Health Analytics/NPR, November 2014, http://truvenhealth.com/Portals/0/NPR-Truven-Health-Poll/NPRPulseDataPrivacy_Nov2014.pdf