David Kwiatkowski, whom prosecutors have called a "serial infector," is charged with stealing painkillers from New Hampshire's Exeter Hospital and replacing them with saline-filled syringes tainted with his own blood. He pleaded not guilty earlier this month to 14 federal drug charges and has been in jail since his arrest in July.

Thirty-two New Hampshire patients have tested positive for the same strain of the liver-destroying disease Kwiatkowski carries, and a dozen other cases have emerged in some of the 18 hospitals in seven states where he previously worked.

Maryland health officials announced four new cases on Friday, all involving patients at The Johns Hopkins Hospital, where Kwiatkowski worked from July 2009 to January 2010.

The previously reported cases include one from the Baltimore VA Medical Center and six from Hays Medical Center in Kansas. Another case has been confirmed at the University of Pittsburgh Medical Center in Pennsylvania, a hospital spokeswoman told The Associated Press this week.

Over the years, Kwiatkowski was fired twice over allegations of drug use and theft, including from UPMC, where he was just a few weeks into his temporary stint when a co-worker accused him of swiping a fentanyl syringe from an operating room and sticking it down his pants. Citing a lack of evidence, hospital authorities didn't call police, and neither the hospital nor the medical staffing agency that placed him in the job informed the national accreditation organization for radiological technicians.

In Maryland, the Department of Health and Mental Hygiene said Friday that no drug diversion allegations involving Kwiatkowski were reported to the agency during his time there, but the five linked cases adds to the concern that such activity took place. The department expects to release a report early next year on potential vulnerabilities and steps to prevent future outbreaks.

Kwiatkowski was sent to Johns Hopkins by a staffing agency that assured the hospital it had followed a vigorous vetting process, hospital spokeswoman Kim Hoppe said.

"This includes a criminal background check, credentials and licensure verification, health and drug screening and two references," she said. "In this case, none of the information that Medical Solutions provided about this health care worker suggested a history of drug diversion or any other criminal activity."