Communicable disease threats report, 19 - 25 April 2025, week 17

This week’s topics Week 17, 19–25 April 2025 1. Overview of respiratory virus epidemiology in the EU/EEA 2. Influenza A(H5N1) – Multi-country (World) – Monitoring human cases 3. Avian influenza A(H9N2) – Multi-country (World) – Monitoring human cases 4. Poliomyelitis – Multi-country – Monthly monitoring of global outbreaks 5. Autochthonous chikungunya virus disease – Réunion and Mayotte, France, 2024–2025 Executive Summary Overview of respiratory virus epidemiology in the EU/EEA Respiratory virus activity is decreasing overall in the European Union/European Economic Area (EU/EEA) but remains elevated in some countries affected by ongoing flu and/or RSV epidemics. Overall influenza activity peaked in week 6, 2025 and continues to decrease. Most of the reporting countries have returned to baseline or low levels of influenza intensity. Co-circulation of influenza A and B viruses continues. RSV activity is lower than at the peak in week 52, 2204 but remains elevated. The greatest impact in secondary care has been in adults aged 45 years and above for influenza (with the impact increasing with age) and in children under five years for RSV. Excess mortality was observed between week 51, 2024 and week 9, 2025, affecting adults aged 45 years and above, with levels now having returned to the expected range. SARS-CoV-2 activity remains at a low level. Influenza A(H5N1) – Multi-country (World) – Monitoring human cases • Vietnamese authorities have reported a human case of...