Assessing influenza activity variations in the Asian region during the pre- and post-pandemic period (2017–2023)

Abstract

Background The year 2021 witnessed a decline in seasonal influenza cases across Southeast Asia and the broader Asian region. However, a sudden surge in influenza cases during 2022–2023 necessitates comprehensive exploration and analysis to inform future prediction models. Objective Our study aims to evaluate the disease burden of influenza in Asian countries post-COVID-19, while comparing seasonal variations to the pre-pandemic influenza patterns. Methods We conducted an extensive analysis of data spanning from January 2017 to September 2023 across ten Asian countries, categorizing them into three WHO regions. Data was sourced from the WHO Flunet system, falling under the purview of the WHO Global Influenza Program. Findings and conclusion In conclusion, influenza epidemiology during the inter-pandemic period is characterized by seasonality influenced by factors such as population contact patterns, virus survival, and host immunity. The year 2020 witnessed a global decrease in influenza circulation due to widespread lockdowns and travel restrictions. However, a resurgence was observed in late 2021, notably with out-of-season activity in the Southern Hemisphere. Our analysis based on reviews indicates a probable significant increase in influenza cases in the upcoming seasons. To address this, the implementation of influenza vaccination programs and the promotion of vaccination for both children and adults are essential measures to alleviate the dual burden of influenza in the post-COVID era.