MILWAUKEE (AP) -- A southeastern Wisconsin health care provider says about 43,000 patient records may be at risk because of a computer hacker.

Froedtert Health says a virus allowed access to a staff member's computer, which compromised patient files that include personal information. Froedtert says there's no evidence the information has been accessed or misused, but the health provider sent letters to patients this week as a precaution.

The Journal Sentinel says fewer than 3 percent of the files contained Social Security numbers.

The patients were treated Froedtert Hospital in Wauwatosa; Community Memorial Hospital in Menomonee Falls; St. Joseph's Hospital near West Bend and Froedtert Health Medical Group, formerly known as Medical Associates of Menomonee Falls and the West Bend Clinic.