Introduction - Influenza is an infection that can be nosocomial in origin, but nosocomial transmission is poorly documented, particularly in short-stay settings. A study was conducted at Édouard Herriot Hospital in Lyon to describe cases of nosocomial influenza and any potential in-hospital transmission. Methods - Over three winter seasons from 2004 to 2007, hospitalized patients and healthcare workers presenting with influenza-like illness were included in this study. For each case, medical data were collected and a nasal swab was taken to establish the virological diagnosis. Cases were defined as follows: index cases, secondary cases, community-acquired cases, and nosocomial cases. The case’s daily contacts were documented to describe potential transmissions that may have occurred within the hospital. Results - Among the 276 individuals included in the study, confirmed influenza was identified in 61 people (22%). Nosocomial transmission was identified in 11 patients (28%) and 10 healthcare workers (45%). Potential transmissions were observed during each season. Conclusion - The presence of nosocomial influenza as well as cases of human-to-human transmission within the facility each season underscore the importance of hygiene measures and vaccination. (R.A.)