An unauthorized party accessed systems at Oakdale, Calif.-based Oak Valley Hospital District and was able to gain access to files that contained patient data.
On July 18, the hospital noticed suspicious activity on its systems and launched an investigation into the incident.
The investigation revealed that an unauthorized party gained access to its systems between April 21 and July 18, gaining access to files that contained patient information, according to a Sept. 15 news release from Oak Valley.
The following patient information was in the files: names, health insurance information and information regarding their care. For some patients, Social Security numbers may have also been compromised.
Oak Valley is currently mailing letters to all affected patients.
The hospital did not mention how many patients were affected.