Influenza Virus Characteristics in Department of Defense Populations, 2024-2025

The influenza virus constantly evolves through antigenic shift and drift, requiring annual review to inform the development of seasonal influenza vaccines. The Department of Defense Global Respiratory Pathogen Surveillance Program and Global Emerging Infections Surveillance program-funded partner laboratories perform routine respiratory pathogen surveillance across a wide-reaching global network of service members and their beneficiaries, U.S. civilians, and some foreign national populations. This report describes the influenza viruses circulating during the 2024-2025 influenza season.