Early Prediction of Type‐Specific Influenza Incidence Using Wastewater‐Based Epidemiology

ABSTRACT This study aimed to predict type‐specific influenza incidence using viral RNA concentrations in wastewater. The RNA concentrations of influenza A and B viruses were measured in weekly wastewater samples collected from three treatment plants in Osaka Prefecture, Japan, between April 2023 and April 2025. Influenza cases in the catchment were apportioned by type using pathogen surveillance data. Models were developed to predict influenza A and B cases per sentinel health surveillance based on viral RNA concentrations in wastewater for the first 69 weeks using hierarchical multiple regression analysis. Their performance was validated over the subsequent 31 weeks. Type‐specific influenza cases were predicted with high accuracy ( R 2 = 0.859 for influenza A + B cases during the validation period). Influenza incidence estimation through wastewater‐based epidemiology is useful for public health measures such as hospital bed allocation because it can provide information approximately 1 week earlier than clinical data publications under same‐day laboratory analysis.