Incidence of hospital-acquired influenza in adults: A prospective surveillance study from 2004 to 2017 in a French tertiary care hospital

•The burden of hospital-acquired influenza (HAI) is not fully understood.•Having an underlying disease important characteristic hospitalized ILI.•HAI occurred at a rate 1 in 13 with influenza-like-illness (ILI) hospital.•The incidence HAI was highest the geriatric ward and increased over time.•HAI rates approximate those reported for Clostridium difficile. BackgroundHospital-acquired potentially leads to significant morbidity mortality already vulnerable patients, but its overall understood. We undertook this study estimate trends laboratory-confirmed among adults, compare clinical characteristics between community-acquired cases.MethodsThis prospective surveillance 11 years adults surgery, medicine wards tertiary acute-care hospital Lyon, France. Nasal swabs were systematically collected from ILI tested by reverse transcriptase-polymerase chain reaction national reference laboratory (Lyon, France).ResultsInfluenza confirmed patients who developed during their hospitalization. Having cases. Cardiovascular most frequent condition both influenza-positive influenza-negative patients. Complications more than The period.ConclusionsHospital-acquired poses risk Longitudinal data are essential support better recognition monitoring viral infections hospitals. Hospital-acquired This France). Influenza period.