Excess mortality and hospitalisations associated with respiratory syncytial virus, influenza, and COVID-19 among adults in Denmark (2015-2024): a modelling study

Amanda Marie Egeskov-Cavling; Chelsea L Hansen; Caroline Klint Johannesen; Birgitte Lindegaard; Samir Bhatt; Cecile Viboud; Thea K Fischer

doi:10.1016/j.lanepe.2025.101396

Excess mortality and hospitalisations associated with respiratory syncytial virus, influenza, and COVID-19 among adults in Denmark (2015-2024): a modelling study

Amanda Marie Egeskov-Cavling^*, Chelsea L Hansen, Caroline Klint Johannesen, Birgitte Lindegaard, Samir Bhatt, Cecile Viboud, Thea K Fischer^*

^*Corresponding author for this work

2 Citations (Scopus)

Abstract

BACKGROUND: Understanding the long-term epidemiology trends of RSV, influenza, and COVID-19 is essential for planning of vaccination strategies and healthcare system epidemic preparedness. This is the first study to provide a comprehensive estimation of both excess mortality and hospitalisations among adults for these respiratory viruses in a European setting. We aim to estimate excess mortality and excess hospitalisations for RSV, influenza, and COVID-19 among adults ≥18 years in Denmark from January 2015 to March 2024.

METHODS: This nationwide time-trend modelling study investigates weekly mortality and hospitalisation rates surpassing the seasonal baseline for RSV, influenza, and COVID-19 among adults in Denmark. Data from the Cause of Death Register, the Danish National Patient Registry, and respiratory virus surveillance data were analysed with Generalized Additive Models (GAM) using a negative binomial likelihood function, including RSV, influenza, COVID-19 variants, and time effects to account for seasonality and trend.

FINDINGS: We estimated 3944 RSV-attributed, 5675 influenza-attributed, and 5636 COVID-19-attributed deaths. Among adults aged 65 or older, the annual mortality rates were 31.2 per 100,000 for RSV, 42.9 for influenza, and 88.5 for COVID-19. Furthermore, we estimated annual admission rates for those aged 65 and older of 177.4 per 100,000 for RSV, 164.6 for influenza, and 398.7 for COVID-19.

INTERPRETATION: This modelling study reveals a substantial impact of RSV on individuals aged 65 and older, with a notable increase in RSV-attributed deaths and hospitalisations in recent years likely due to expanded respiratory testing after the COVID-19 pandemic. Our findings highlight the need for increased awareness in previously considered lower-risk patients, and establish benchmarks for evaluating preventive interventions.

FUNDING: This study received funding from Independent Research Fund Denmark.

Original language	English
Article number	101396
Journal	The Lancet regional health. Europe
Volume	55
Pages (from-to)	101396
DOIs	https://doi.org/10.1016/j.lanepe.2025.101396
Publication status	Published - Aug 2025

Keywords

Adults
Burden of disease
COVID19
Hospital admission
Influenza
Mortality
RSV
Respiratory tract infections
Time series analysis

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10.1016/j.lanepe.2025.101396

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Egeskov-Cavling, A. M., Hansen, C. L., Johannesen, C. K., Lindegaard, B., Bhatt, S., Viboud, C., & Fischer, T. K. (2025). Excess mortality and hospitalisations associated with respiratory syncytial virus, influenza, and COVID-19 among adults in Denmark (2015-2024): a modelling study. The Lancet regional health. Europe, 55, 101396. Article 101396. https://doi.org/10.1016/j.lanepe.2025.101396

Excess mortality and hospitalisations associated with respiratory syncytial virus, influenza, and COVID-19 among adults in Denmark (2015-2024): a modelling study. / Egeskov-Cavling, Amanda Marie; Hansen, Chelsea L; Johannesen, Caroline Klint et al.
In: The Lancet regional health. Europe, Vol. 55, 101396, 08.2025, p. 101396.

Research output: Contribution to journal › Journal article › Research › peer-review

Egeskov-Cavling, AM, Hansen, CL, Johannesen, CK , Lindegaard, B, Bhatt, S, Viboud, C & Fischer, TK 2025, 'Excess mortality and hospitalisations associated with respiratory syncytial virus, influenza, and COVID-19 among adults in Denmark (2015-2024): a modelling study', The Lancet regional health. Europe, vol. 55, 101396, pp. 101396. https://doi.org/10.1016/j.lanepe.2025.101396

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title = "Excess mortality and hospitalisations associated with respiratory syncytial virus, influenza, and COVID-19 among adults in Denmark (2015-2024): a modelling study",

abstract = "BACKGROUND: Understanding the long-term epidemiology trends of RSV, influenza, and COVID-19 is essential for planning of vaccination strategies and healthcare system epidemic preparedness. This is the first study to provide a comprehensive estimation of both excess mortality and hospitalisations among adults for these respiratory viruses in a European setting. We aim to estimate excess mortality and excess hospitalisations for RSV, influenza, and COVID-19 among adults ≥18 years in Denmark from January 2015 to March 2024.METHODS: This nationwide time-trend modelling study investigates weekly mortality and hospitalisation rates surpassing the seasonal baseline for RSV, influenza, and COVID-19 among adults in Denmark. Data from the Cause of Death Register, the Danish National Patient Registry, and respiratory virus surveillance data were analysed with Generalized Additive Models (GAM) using a negative binomial likelihood function, including RSV, influenza, COVID-19 variants, and time effects to account for seasonality and trend.FINDINGS: We estimated 3944 RSV-attributed, 5675 influenza-attributed, and 5636 COVID-19-attributed deaths. Among adults aged 65 or older, the annual mortality rates were 31.2 per 100,000 for RSV, 42.9 for influenza, and 88.5 for COVID-19. Furthermore, we estimated annual admission rates for those aged 65 and older of 177.4 per 100,000 for RSV, 164.6 for influenza, and 398.7 for COVID-19.INTERPRETATION: This modelling study reveals a substantial impact of RSV on individuals aged 65 and older, with a notable increase in RSV-attributed deaths and hospitalisations in recent years likely due to expanded respiratory testing after the COVID-19 pandemic. Our findings highlight the need for increased awareness in previously considered lower-risk patients, and establish benchmarks for evaluating preventive interventions.FUNDING: This study received funding from Independent Research Fund Denmark.",

keywords = "Adults, Burden of disease, COVID19, Hospital admission, Influenza, Mortality, RSV, Respiratory tract infections, Time series analysis",

author = "Egeskov-Cavling, \{Amanda Marie\} and Hansen, \{Chelsea L\} and Johannesen, \{Caroline Klint\} and Birgitte Lindegaard and Samir Bhatt and Cecile Viboud and Fischer, \{Thea K\}",

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year = "2025",

month = aug,

doi = "10.1016/j.lanepe.2025.101396",

language = "English",

volume = "55",

pages = "101396",

journal = "The Lancet regional health. Europe",

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T1 - Excess mortality and hospitalisations associated with respiratory syncytial virus, influenza, and COVID-19 among adults in Denmark (2015-2024)

T2 - a modelling study

AU - Egeskov-Cavling, Amanda Marie

AU - Hansen, Chelsea L

AU - Johannesen, Caroline Klint

AU - Lindegaard, Birgitte

AU - Bhatt, Samir

AU - Viboud, Cecile

AU - Fischer, Thea K

PY - 2025/8

Y1 - 2025/8

N2 - BACKGROUND: Understanding the long-term epidemiology trends of RSV, influenza, and COVID-19 is essential for planning of vaccination strategies and healthcare system epidemic preparedness. This is the first study to provide a comprehensive estimation of both excess mortality and hospitalisations among adults for these respiratory viruses in a European setting. We aim to estimate excess mortality and excess hospitalisations for RSV, influenza, and COVID-19 among adults ≥18 years in Denmark from January 2015 to March 2024.METHODS: This nationwide time-trend modelling study investigates weekly mortality and hospitalisation rates surpassing the seasonal baseline for RSV, influenza, and COVID-19 among adults in Denmark. Data from the Cause of Death Register, the Danish National Patient Registry, and respiratory virus surveillance data were analysed with Generalized Additive Models (GAM) using a negative binomial likelihood function, including RSV, influenza, COVID-19 variants, and time effects to account for seasonality and trend.FINDINGS: We estimated 3944 RSV-attributed, 5675 influenza-attributed, and 5636 COVID-19-attributed deaths. Among adults aged 65 or older, the annual mortality rates were 31.2 per 100,000 for RSV, 42.9 for influenza, and 88.5 for COVID-19. Furthermore, we estimated annual admission rates for those aged 65 and older of 177.4 per 100,000 for RSV, 164.6 for influenza, and 398.7 for COVID-19.INTERPRETATION: This modelling study reveals a substantial impact of RSV on individuals aged 65 and older, with a notable increase in RSV-attributed deaths and hospitalisations in recent years likely due to expanded respiratory testing after the COVID-19 pandemic. Our findings highlight the need for increased awareness in previously considered lower-risk patients, and establish benchmarks for evaluating preventive interventions.FUNDING: This study received funding from Independent Research Fund Denmark.

AB - BACKGROUND: Understanding the long-term epidemiology trends of RSV, influenza, and COVID-19 is essential for planning of vaccination strategies and healthcare system epidemic preparedness. This is the first study to provide a comprehensive estimation of both excess mortality and hospitalisations among adults for these respiratory viruses in a European setting. We aim to estimate excess mortality and excess hospitalisations for RSV, influenza, and COVID-19 among adults ≥18 years in Denmark from January 2015 to March 2024.METHODS: This nationwide time-trend modelling study investigates weekly mortality and hospitalisation rates surpassing the seasonal baseline for RSV, influenza, and COVID-19 among adults in Denmark. Data from the Cause of Death Register, the Danish National Patient Registry, and respiratory virus surveillance data were analysed with Generalized Additive Models (GAM) using a negative binomial likelihood function, including RSV, influenza, COVID-19 variants, and time effects to account for seasonality and trend.FINDINGS: We estimated 3944 RSV-attributed, 5675 influenza-attributed, and 5636 COVID-19-attributed deaths. Among adults aged 65 or older, the annual mortality rates were 31.2 per 100,000 for RSV, 42.9 for influenza, and 88.5 for COVID-19. Furthermore, we estimated annual admission rates for those aged 65 and older of 177.4 per 100,000 for RSV, 164.6 for influenza, and 398.7 for COVID-19.INTERPRETATION: This modelling study reveals a substantial impact of RSV on individuals aged 65 and older, with a notable increase in RSV-attributed deaths and hospitalisations in recent years likely due to expanded respiratory testing after the COVID-19 pandemic. Our findings highlight the need for increased awareness in previously considered lower-risk patients, and establish benchmarks for evaluating preventive interventions.FUNDING: This study received funding from Independent Research Fund Denmark.

KW - Adults

KW - Burden of disease

KW - COVID19

KW - Hospital admission

KW - Influenza

KW - Mortality

KW - RSV

KW - Respiratory tract infections

KW - Time series analysis

UR - https://www.scopus.com/pages/publications/105010964474

U2 - 10.1016/j.lanepe.2025.101396

DO - 10.1016/j.lanepe.2025.101396

M3 - Journal article

C2 - 40727239

SN - 2666-7762

VL - 55

SP - 101396

JO - The Lancet regional health. Europe

JF - The Lancet regional health. Europe

M1 - 101396

ER -

Excess mortality and hospitalisations associated with respiratory syncytial virus, influenza, and COVID-19 among adults in Denmark (2015-2024): a modelling study

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