The hospitalization burden of influenza: just the tip of the iceberg?

Introduction: The codes used to report hospital admissions due to influenza viruses are likely to underestimate the real incidence of influenza-related cases. Methods: In order to estimate this burden we ran a negative binomial model, in which the numbers of weekly admissions for respiratory and cardiovascular diseases were regressed based on influenza syndrome surveillance data (InfluNet), average temperature and seasonality terms. Results: On average over the 2008-2015 period, in addition to 4,407 admissions coded as influenza, we estimated 15,206 additional admissions attributable to influenza. Overall, the total estimated hospital burden attributable to influenza/influenza-like cases is about €37m per year. Discussion: This estimate should be used for policy making (e.g., vaccine strategies) and operation management choices (e.g., planning and staffing beds during influenza peaks) and encourage the involvement of general practitioners and pediatricians for early symptom control to avoid hospitalization for less severe cases