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

Summary

Among 214,730 SARI cases, testing coverage was high (82% SARS-CoV-2, 73% influenza, 53% RSV) and epidemic peaks were driven by these pathogens. Median time to ICD-10 coding was 5 days, while nowcasting and alternative case definitions improved timeliness, especially in younger populations where including URIs increased capture.

Key Findings

• Identified 214,730 SARI cases; testing coverage was 82% for SARS-CoV-2, 73% for influenza, and 53% for RSV.
• Median time from admission to SARI ICD-10 coding was 5 days (IQR 3–10); nowcasting and alternative case definitions improved timeliness.
• ICD-10 codes for LRIs and COVID-19 captured only ~55% of cases in ages 0–29 compared with definitions including URIs.

Clinical Implications

Implement permanent registry-based SARI surveillance with nowcasting to detect surges early, guide ICU capacity, and tailor responses across age groups; include URI codes to improve case capture in younger populations.

Limitations

• Dependent on coding accuracy and completeness; limited clinical granularity and severity metrics
• Temporary system; external validity to other health systems may vary

Future Directions

Establish permanent SARI surveillance with real-time dashboards; integrate outcomes (ICU, mortality), vaccination status, and genomic data to refine attribution and forecasting.