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. 2025 Feb;19(2):e70080.
doi: 10.1111/irv.70080.

Registry-Based Surveillance of Severe Acute Respiratory Infections in Norway During 2021-2024

Elina Seppälä  1 , Håkon Bøås  1 , Jesper Dahl  1 , Jeanette Stålcrantz  1 , Melanie Stecher  1   2 , Ragnhild Tønnessen  1   3 , Gunnar Øyvind Isaksson Rø  4 , Hilde Kløvstad  1 , Trine Hessevik Paulsen  1
Affiliations

Registry-Based Surveillance of Severe Acute Respiratory Infections in Norway During 2021-2024

Elina Seppälä et al. Influenza Other Respir Viruses. 2025 Feb.

Abstract

Background: In 2021, the Norwegian Institute of Public Health established temporary registry-based surveillance of severe acute respiratory infections (SARI). We aimed to describe the surveillance system and evaluate selected attributes to inform the establishment of a permanent SARI surveillance system.

Methods: SARI cases were defined using ICD-10 discharge codes from national health and administrative registries, including codes for acute upper or lower respiratory infection (URI and LRI), COVID-19, acute respiratory distress syndrome, pertussis or otitis media. Data from polymerase chain reaction (PCR) analyses were available for 10 respiratory pathogens including SARS-CoV-2, influenza virus and respiratory syncytial virus (RSV). We included data from 28 September 2020 to 31 March 2024 and calculated the following parameters: the proportion of cases tested for SARS-CoV-2, influenza virus and/or RSV; time between admission and registration of a SARI-related ICD-10 code; and proportion of cases with URI, LRI and COVID-19.

Results: We identified 214,730 SARI cases, of whom 82%, 73% and 53% were tested for SARS-CoV-2, influenza virus and RSV. Case peaks were predominantly driven by one or a combination of these pathogens. Median time between admission and a registered SARI diagnostic code was 5 (lower-upper quartile 3-10) days. Nowcasting and alternative case definitions for SARI with COVID-19, influenza and RSV improved the timeliness. The ICD-10 codes for LRIs and COVID-19 captured only ~55% of the cases in the age group of 0-29 years compared to the routine case definition, where URIs were included.

Conclusions: Registry-based SARI surveillance provides timely data for handling epidemics of respiratory infections in Norway. We recommend establishing a permanent SARI surveillance system.

Keywords: COVID‐19; RSV; hospitalisation; influenza; registry‐based surveillance; severe acute respiratory infection (SARI).

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

FIGURE 1
FIGURE 1
The key data sources and data flow for the Norwegian surveillance system for severe acute respiratory infections (SARI), 2021–2024.
FIGURE 2
FIGURE 2
Weekly number of admissions per 100,000 with severe acute respiratory infection (SARI), SARI‐COVID‐19, SARI‐influenza and SARI‐RSV, Norway, 28 September 2020–31 March 2024.
See this image and copyright information in PMC

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