- (1) report using a needle or syringe after someone else 2 or more different times in the past 3 months and (2) report using a needle or syringe after 3 or more different persons in the past 3 months. (This second criterion could be met in 3 episodes of injection with a single injection partner, if the participant used a needle or syringe after a different person each time. Alternatively, the criterion could be met in a single episode of injection, if the participant used a needle or syringe after 3 or more persons had used a single set of works.)