Ceará Confirms Three Cases of H3N2 Subclade K in Fortaleza Area

Overview

• The state identified three H3N2 subclade K detections from samples collected in Fortaleza and Caucaia between January 4 and February 7, corresponding to epidemiological weeks 1 to 5.
• Laboratory confirmation was carried out by the National Influenza Center at the Evandro Chagas Institute (NIC/IEC) and detailed in a Ceará Health Department technical note published on February 22.
• Authorities characterize K as a genetic variation within seasonal H3N2, with symptoms similar to typical influenza and no current evidence of increased severity.
• The influenza vaccine offered through Brazil’s public health system is reported to cover the K subclade, with the 2026 immunization campaign yet to begin.
• Officials underscore H3N2’s higher mutation rate relative to H1N1, reinforcing the need for continued surveillance, following Brazil’s first K detection in Pará in December and prior WHO/PAHO alerts.