This undated file photo provided by the U.S. Attorney's Office in New Hampshire shows David Kwiatkowski, a former lab technician at Exeter, N.H. Hospital Kwiatkowski was arrested in July at a hospital in Massachusetts where he was receiving medical treatment and charged in New Hampshire with tampering with needles and infecting at least 31 people who were treated at Exeter Hospital's cardiac catheterization lab with hepatitis C. Thousands more people treated at hospitals where he worked are being tested. Records and interviews conducted by The Associated Press show that authorities could have halted Kwiatkowski's career four years ago, after he was fired from a Pittsburgh hospital. But he went on to work at 10 more hospitals, none of which knew about his history.