Changed epidemiology of influenza and RSV hospitalizations after the emergence of SARS-CoV-2 in Norway, 2017 – 2024.

Publication date: Jun 19, 2025

Many countries reported missing and atypical influenza and RSV seasons during the COVID-19 pandemic. Here we describe the incidence and seasonality of COVID-19, influenza, and RSV hospitalizations in Norway between 2017-2024, and the disease burden between 2022-2024. Using nationwide data on ICD-10 discharge codes, procedure codes and laboratory results, we calculate the incidence of COVID-19, influenza, and RSV hospitalizations, by age group, week and surveillance year between January 2017 to April 2024, and report proportions receiving intensive care, deaths and length of stay between 2022-2024. The transmission of influenza and RSV was interrupted the first year of the COVID-19 pandemic and reemerged with epidemics outside of the normal seasonality in 2021/2022, after COVID-19 restrictions were removed. Between 2022-2024, COVID-19 was a greater contributor to hospitalizations than influenza and RSV, with higher mortality rate within two weeks of admission. The use of ventilatory support/intensive care admission was highest among patients hospitalized with RSV. The transmission of influenza and RSV was interrupted during the first year of the COVID-19 pandemic, followed by an unusual seasonality. Although many hospitalizations are caused by RSV and influenza, COVID-19 was the largest contributor of these three to hospital burden in the first years with co-circulation.

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Concepts Keywords
Hospitalizations COVID-19
Influenza Disease Burden
Norway influenza
Surveillance Length of stay

Semantics

Type Source Name
disease MESH influenza
disease MESH COVID-19 pandemic
disease MESH respiratory infections
disease MESH Infection
disease MESH Emergency
disease MESH Communicable Diseases
disease MESH death
disease IDO infectious agent

Original Article

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