An EMT was stabbed by a maniac on a Queens street Thursday afternoon — in an unprovoked attack that occurred as she went to grab food, authorities said. Lt. Alison Russo-Elling, a 61-year-old department veteran who was a World Trade Center responder on Sept. 11, 2001, was stabbed multiple times by an assailant at 20th Avenue and 41st Street around 2:20 p.m., police said. She was on duty at the time and was about half-block from Station 49 on the sidewalk when she was attacked, NYPD Chief of Detectives James Essig said.