Banner Health data breach affects more than 50,000

Phoenix-based not-for-profit health system Banner Health accidentally exposed personal information of more than 50,000 people in a gaffe that resulted in their Medicare identification or Social Security numbers showing up on magazine address labels.

The identification numbers were printed on address labels attached to the winter 2014 edition of Banner Health's quarterly magazine, Smart & Healthy, though it is currently unclear how many of the labels showed Social Security numbers versus how many revealed alternate Medicare identification numbers. It is also not clear at this time how the error occurred.

A spokesperson for the health system confirmed the incident. Banner Health told the Arizona Republic newspaper Monday that it is investigating what went wrong and that health system officials will send a letter to those affected.

Magazine recipients are members of Banner's Medicare Pioneer accountable care organization. Though Banner operates in seven states, the magazines in question were only mailed to addresses in Arizona, with most of those going to Maricopa County, where Phoenix is located.

Follow Rachel Landen on Twitter: @MHrlanden