WHO and PAHO Warn of Early Flu Uptick Driven by H3N2 ‘K’ Subclade

Overview

• The WHO says seasonal influenza has increased globally since October, with H3N2 responsible for the largest share of infections.
• Overall activity remains within expected seasonal ranges, though some regions are seeing earlier or stronger circulation than usual.
• The J.2.4.1 genetic subclade, widely referred to as “gripe K,” has grown since August with detections across Europe, Asia, and North America, yet available data do not indicate more severe illness.
• WHO and PAHO call for expanded vaccination and early diagnosis for vulnerable groups, emphasizing that current vaccines still provide protection against drifted viruses and other included strains.
• Preliminary analyses cited by WHO indicate vaccines are reducing hospitalizations this season—around 70–75% in children and 30–40% in adults—while southern South America’s earlier 2025 wave was driven mainly by H1N1 pdm09.