Work

Clinical outcomes during the 2025-2026 and 2024-2025 influenza seasons in a US EHR network: an ecological comparison during A(H3N2) subclade K predominance

Year: 2026

Type: article

Abstract: Background The influenza A(H3N2) subclade K virus has predominated in the 2025–2026 season. This study compared the clinical severity of influenza between 2025–2026 and 2024–2025 seasons. Methods In this retrospective cohort study, a multicenter electronic health record database (TriNetX) was used. The clinical outcomes following influenza infection confirmed by nucleic acid detection were ecologically compared between the 2025–2026 and 2024–2025 seasons with propensity score matching. Results There were 8,965 and 8,937 children and 7,488 and 6,947 adults with confirmed influenza A(H3N2) infection in the 2025–2026 and 2024–2025 seasons, respectively. Following each propensity score matching, the odds ratios for children and adults were not assessed (due to the small number of events) and 0.87 [95% confidence interval 0.71–1.05]; p=0.148 for death, 1.32 [1.10–1.59]; p=0.003 and 0.91 [0.82–1.02]; p=0.092 for critical care admission, 1.06 [0.97–1.16]; p=0.191 and 1.01 [0.94–1.08]; p=0.083 for hospitalization, 0.88 [0.73–1.07]; p=0.197 and 0.93 [0.83–1.04]; p=0.194 for mechanical ventilation and 1.10 [0.91–1.32]; p=0.320 and 0.93 [0.83–1.03]; p=0.177 for vasopressor use, respectively.. Conclusions In this EHR-based season-level comparison, no consistent adjusted differences were observed; however, the study could not directly assess subclade K-specific severity or rule out clinically relevant differences. Rapid and timely monitoring of clinical characteristics and severity in case of an emerging influenza strain or subclade is important to guide preventive and therapeutic strategies against influenza.

Source: IJID Regions

DOI: 10.1016/j.ijregi.2026.101025

Authors: Taito Kitano, Sayaka Yoshida

Institutions: Nara Prefecture General Medical Center, Japan Institute for Health Security

Language: English

Topic: Influenza Virus Research Studies

Subfield: Epidemiology

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: gold

Estimated APC paid: $1,380