Wastewater-Based Surveillance of Respiratory Syncytial Virus Epidemic at the National Level in Finland

The purpose of this study was to evaluate the potential of wastewater-based surveillance in the monitoring of epidemics at the national level in Finland. The 2021-2022 respiratory syncytial virus epidemic in Finland was analyzed from wastewater and the Finnish National Infectious Diseases Register. The study was performed using 150 samples that were collected monthly from May 2021 to July 2022 from ten wastewater treatment plants that cover 40% of the Finnish population. Respiratory syncytial virus detection in 24 h composite samples of influent wastewater was performed using reverse-transcription quantitative polymerase chain reaction (RT-qPCR). Respiratory syncytial virus wastewater data were positively correlated with the National Infectious Diseases Register-based sampling week incidence (correlation coefficient, CC min = 0.412, max = 0.865) and the four-week cumulative incidence (CC min = 0.482, max = 0.814), showing the potential of wastewater-based surveillance in estimating the course of epidemics. When the register-based incidence of respiratory syncytial virus was at least four cases/100,000 persons/sampling week, it was detected in all wastewater samples. This study showed that wastewater surveillance can be used to surveil respiratory syncytial virus epidemics at the national level, and its potential in the surveillance of other epidemics should be explored further.