Background Data on influenza in the healthcare setting are often based on retrospective investigations of outbreaks and a few studies described influenza during several consecutive seasons. The aim of the present work is to report data on influenza like illness (ILI) and influenza from 5-year prospective surveillance in a short-stay geriatrics unit. Findings A short stay geriatrics unit underwent 5 years of ILI surveillance from November 2004 to March 2009, with the aim of describing ILI in a non-outbreak context. The study was proposed to patients who presented ILI, defined as fever >37.8°C or cough or sore throat. Among 1,353 admitted patients, 115 presented an ILI, and 34 had hospital-acquired ILI (HA-ILI). Influenza was confirmed in 23 patients, 13 of whom had been vaccinated. Overall attack rates were 2.78% and 0.02% for HA-ILI and HA-confirmed influenza respectively, during the 5 seasons. Conclusions This 5-year surveillance study supports the notion that influenza infections are common in hospitals, mostly impacting the elderly hospitalized in short-stay units. It highlights the need for appropriate control measures to prevent HA-ILI in geriatric units and protect elderly patients.