Robert Fowler of Seabrook was diagnosed with the blood-borne viral disease in June, 14 months after he underwent a cardiac catheterization at Exeter Hospital. Fowler was treated at the hospital’s cardiac lab a month after it hired David Kwiatkowski, who is accused of stealing anesthetic drugs from the lab, injecting himself and contaminating syringes that were later used on patients. In a lawsuit filed Sunday in federal court in Nebraska, Boston lawyer Domenic Paolini alleges that Triage Staffing Inc. was negligent in hiring, employing and supervising Kwiatkowski as a traveling technician and in sending him to Exeter.