A laptop computer containing information on 4,310 patients was stolen from a University of California at San Francisco School of Medicine employee on Nov. 30, 2009, and has since been recovered.
The laptop files included data on UCSF patients and their treatment from 2008 and 2009. The laptop also had patient data files from the worker's prior employer, 621-bed Beth Israel Deaconess Medical Center in Boston.
Patient names, medical record numbers, ages and clinical information were on the computer. The files didn't have Social Security numbers or other financial data for the patients, according to UCSF.
Both UCSF and Beth Israel Deaconess sent letters to patients about the data security breach in January.
The laptop was recovered on Jan. 8. There is no evidence of unauthorized access to the files or the laptop, UCSF said in a news release.
UCSF said it is continually modifying its systems to enhance security.