A traveling hospital worker accused of stealing drugs and infecting patients with hepatitis C through contaminated syringes has pleaded not guilty to the charges in New Hampshire federal court.

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 only said “yes” when asked in court Monday if he understood his rights. Trial was set for the first week of February.

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 in 18 hospitals in seven states. Patients in Arizona, Georgia, Kansas (Hays), Maryland, Michigan, New York and Pennsylvania have since been tested for hepatitis C.