Froedtert Health, a three-hospital health system based in Milwaukee, announced  a data breach, reporting that one of its employee’s computer account was hacked. The breach, according to a report from the Milwaukee-Wisconsin Journal Sentinel, may have affected more than 40,000 patients, although the health system says it found no evidence that any personal information or medical records were accessed.

Froedtert Health’s officials learned of the breach on Dec. 14, 2012, but did not clarify when it actually happened. To examine what happened, the health system hired a computer forensics company, which couldn’t rule out the possibility the virus was able to obtain information stored in the employee's work computer account. The health system did note the computer contained a file with some patients’ information, including names, addresses, telephone numbers, dates of birth, medical record numbers, names of health insurers, diagnoses, other clinical information, and in some instances Social Security numbers.

Recently, the Carpinteria, Calif.-based Redspin Inc., a provider of IT security assessments, issued a report that found of large-scale health data breaches increased from 2011 to 2012.