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. 2025 Dec;21(1):2440206.
doi: 10.1080/21645515.2024.2440206. Epub 2025 Jan 27.

Disease burden of influenza in Spain: A five-season study (2015-2020)

Iván Sanz-Muñoz  1   2   3 , Irene Arroyo-Hernantes  4 , Alejandro Martín-Toribio  1   5 , Marina Toquero-Asensio  1   2 , Javier Sánchez-Martínez  1   2 , Carla Rodríguez-Crespo  1   2 , Silvia Rojo-Rello  1   4 , Marta Domínguez-Gil  1   6 , Marta Hernández-Pérez  1   5 , Eduardo Tamayo  5   7   8 , Ruth Gil-Prieto  9 , Ángel Gil-de-Miguel  9   10 , José M Eiros  1   4   5   6
Affiliations

Disease burden of influenza in Spain: A five-season study (2015-2020)

Iván Sanz-Muñoz et al. Hum Vaccin Immunother. 2025 Dec.

Abstract

Influenza accounts for 30% of the total morbidity and mortality in the European Union. However, the specific burden in different European countries is largely unknown, and more research is needed to ascertain the reality of this disease. In this retrospective study, we analyzed the burdens of hospitalization, intensive care unit (ICU) admission and in-hospital mortality in Spain over five seasons (2015-2020) via publicly available Minimum Basic Datasets (MDBS). The data revealed that influenza had a major impact in Spain, with approximately 29,000 hospitalizations, 2,200 ICU admissions, and 1,600 deaths each season. In this period, approximately 7.8% of those hospitalized required ICU admission, and 5.7% died in the hospital due to influenza, with wide differences in these parameters depending on the season due to the virological characteristics of the major circulating viruses. More than 60% of those hospitalized were over 65 years of age, and approximately 82% of those who died were elderly, demonstrating that the greatest burden of hospitalization and mortality is centered on this age group. The annual direct cost of influenza was approximately €128 million per season, with more than 80% of this cost centered on people over 45 years of age.

Keywords: Influenza; burden of disease; economic burden; in-hospital mortality; length of stay.

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Conflict of interest statement

No potential conflict of interest was reported by the author(s).

Figures

Figure 1.
Figure 1.
Hospitalizations, ICU admissions, and deaths associated with an influenza diagnosis in Spain between 2015–2016 and 2019–2020. Figures 1a and 1b present the number and prevalence of hospitalizations of patients with influenza, respectively. Figures 1c and 1d present the number and proportion of patients admitted to the ICU. Figures 1e and 1f present the number and proportion of deaths (in-hospital death rate), respectively.
Figure 2.
Figure 2.
Hospitalizations, ICU admissions, and deaths associated with an influenza diagnosis in Spain between 2015–2016 and 2019–2020 by age group. Figures 2a and 2b present the number and prevalence of hospitalizations for influenza, respectively. Figures 2c and 2d present the number and proportion of patients admitted to the ICU. Figures 2e and 2f present the number and proportion of deaths (in-hospital death rate), respectively.
Figure 3.
Figure 3.
Average length of stay (LoS) of hospitalization and ICU admissions with an influenza diagnosis in Spain between 2015–2016 and 2019–2020 by season and age group. Figure 3a represents the average LoS by season, whereas figures 3b and 3c represent the average LoS by age group in hospitalized patients and those admitted to the ICU, respectively.
Figure 4.
Figure 4.
Average direct health care cost (DHCC) in € of influenza cases diagnosed in Spain between 2015–2016 and 2019–2020 by season and age group. Figures 4a and 4b represent the average and total DHCCs by season, respectively, whereas figures 4c and 4d represent the average and total DHCCs by age group, respectively.
See this image and copyright information in PMC

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