CONCORD, N.H. — A hospital worker accused of injecting himself with stolen drugs and contaminating syringes that infected at least 30 patients with hepatitis C was charged Thursday with federal drug crimes.

David Kwiatkowski, a former technician at Exeter Hospital, was arrested Thursday morning at a Massachusetts hospital where he was receiving treatment. U.S. Attorney John Kacavas called Kwiatkowski a “serial infector” who worked in at least six other states, including one in which he is a suspect in a similar incident involving a hospital operating room. Kacavas declined to name any of the other states but said they are not clustered in one part of the country.

“We are closer to the beginning of our investigation than the end,” Kacavas said.

Kwiatkowski, originally from Michigan, worked at Exeter’s cardiac catheterization lab from April 2011 through this past May, when he was fired. He told investigators that he learned he had hepatitis C in May, but Kacavas said there is evidence he had the liver-destroying disease since at least June 2010.

“This serial infector has been contained, and the menace he posed to public health and safety has been removed,” Kacavas said.

Authorities didn’t say in what hospital Kwiatkowski was being treated so he couldn’t be contacted for comment.

Investigators believe Kwiatkowski, 33, stole syringes containing fentanyl, a powerful anesthetic more potent than morphine, and injected himself with them. They said he then put another liquid, such as saline, into the syringes, which were later used for patients. They said a search of his vehicle found an empty fentanyl syringe and several needles.

According to an affidavit, Kwiatkowski sometimes left the lab sweating profusely and attended procedures on his off days. One witness said he appeared to be “on something.” At least once, he was sent home for the day after a colleague told a supervisor that he was unfit to perform medical care, Kacavas said.

Kwiatkowski was what is known as a “traveler,” a technician hired by hospitals for temporary stints around the country. In a statement, Exeter Hospital said he underwent drug testing and a criminal background check when he was hired.

“It is deeply disturbing that the alleged callous acts of one individual can have such an impact on so many innocent lives. As a result of his alleged actions, people in our community, who in many cases are the friends and neighbors of the 2,300 people who work here, now face the challenge of a potentially chronic disease,” hospital president Kevin Callahan said.

The hospital declined to comment further about Kwiatkowski, citing the ongoing investigation.

Hepatitis C is a blood-borne viral infection that can cause liver disease and chronic health issues. Altogether, 31 people, including Kwiatkowski, have tested positive for the same strain of the disease since the investigation began in late May, including an 89-year-old woman who was treated for a heart valve problem in February.

The woman lives with her niece, who also got tested for hepatitis C because she was exposed to the woman’s blood while helping her after she suffered a deep cut on her leg in April. The niece’s test was negative, but she will get tested again in six months, she said Thursday.

The niece, who asked not to be publicly identified because of the stigma associated with the disease and because she wants to protect her aunt from the media, said she hopes the criminal charges will deter others from similar schemes. She said she was happy to hear that Kwiatkowski had been arrested.

She said the ordeal has turned her family’s life upside down.

“We should be able to go into a hospital, put our lives in their hands and know that we’re going to be OK,” she said.

State and local health departments aren’t required to report such outbreaks to the Centers for Disease Control and Prevention, but in a report released in June, the agency said it was notified of 13 outbreaks nationwide between 2008 and 2011. Of those, seven occurred in outpatient facilities; most were traced to unsafe injection practices.

At least two have resulted in criminal charges, including a Colorado woman who was convicted of stealing syringes filled with painkillers from two hospitals where she worked and replacing them with used syringes. The syringes were later used on surgical patients, and up to three dozen patients were found to have hepatitis C after being exposed.

Kacavas said New Hampshire is working with the CDC, law enforcement and departments of public health in other states where Kwiatkowski worked.

“I’m unaware of such a scheme with such reach,” he said. “This one has the potential for very far-reaching implications.”

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