CONCORD, N.H. (AP) -- A traveling hospital worker accused of stealing drugs and infecting patients with hepatitis C through contaminated syringes pleaded not guilty to the charges in federal court on Monday.

David Kwiatkowski, whom prosecutors describe as a "serial infector," was indicted last week on multiple charges of tampering with a consumer product and illegally obtaining drugs.

Kwiatkowski, who was handcuffed, said only "yes" when asked in court if he understood his rights. His trial was scheduled for the first week of February, although U.S. Attorney John Kacavas said given the complexity of the case, it probably would take place later in the year.

Kacavas could not say how much federal prison time Kwiatkowski could get if convicted but said prosecutors will seek a substantial sentence. He said the investigation continues, and further charges against Kwiatkowski could not be ruled out.

Until May, Kwiatkowski worked as a cardiac technologist at Exeter Hospital, where 32 patients were diagnosed with the same strain of hepatitis C he carries. Before that, he worked as a traveling technologist in 18 hospitals in seven states, moving from job to job despite having been fired twice over allegations of drug use and theft.

Thousands of patients in Arizona, Georgia, Kansas, Maryland, Michigan, New York and Pennsylvania have since been tested for hepatitis C, a blood-borne viral infection that can cause liver disease and chronic health issues. In addition to the New Hampshire patients, a handful of patients in Kansas and one in Maryland have been found to carry the strain Kwiatkowski carries.

In Exeter, Kwiatkowski is accused of stealing fentanyl, injecting himself and then re-filling the tainted syringes with saline to be used on patients.

The charges refer to seven incidents between January and March, and were handed up after prosecutors were twice given more time to present the case to the grand jury. In requesting the delays, prosecutors said they were still conducting interviews and complex scientific analysis in multiple states, though the indictments only address Kwiatkowski's time in Exeter.

Though New Hampshire cannot charge him for possible violations in other states, it can use evidence gathered in those jurisdictions in its trial, Kacavas said.

He said other states are waiting to see the outcome of New Hampshire's case before deciding whether to file charges.

Kwiatkowski, who was arrested in July, had suggested that a co-worker had planted a fentanyl syringe found in his car.

Exeter Hospital officials have said that while employees raised concerns about Kwiatkowski's appearance -- some described him as shaky and sweaty -- none suspected him of diverting medication. In each case, Kwiatkowski provided plausible explanations related to either personal medical issues or family crises, the hospital said. Kwiatkowski held the required certification for the job and was given good references from his previous two employers.

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