Emergence of influenza A(H3N2) subclade K in northeast Ohio in autumn 2025
Abstract
KEYWORDS whole-genome sequencing, subclade K, A(H3N2), influenza A newly emerged influenza A(H3N2) subclade, designated K (formerly J.2.4.1), was identified in June 2025 and rapidly spread worldwide (1-3).This drifted subclade exhibits antigenic divergence from the current northern hemisphere vaccine strain (1, 2).Early observations also indicate that subclade K may be contributing to an unusually early start of the 2025-2026 influenza season in several countries (3).Here, we report the identification of subclade K during clinical validation of a laboratory-developed test for influenza A virus (IAV) subtyping by whole-genome sequencing (WGS) and describe its prevalence in northeast Ohio in autumn 2025.A convenience cohort of nasopharynx/nasal swab specimens with IAV detected with cycle threshold
Fields of Study & Subjects
Influenza Virus Research Studies
Respiratory viral infections research
Data-Driven Disease Surveillance
Publication details
- Journal / source
- Journal of Clinical Microbiology
- Publisher
- American Society for Microbiology
- Volume
- 64
- Issue
- 3
- Pages
- e0181325–e0181325
- Publication date
- 27 January 2026
- Language
- EN